35 Cenozoic Creatures As Awesome (Or Even More So) Than Dinosaurs

Hey there every peoples.

Guess what… It’s my 100th post!

When I started this thing 5 years ago, i didn’t know it would grow into the marginal success it is today. But what do you do for such a special occasion? Can’t just be some run of the mill topic. It can’t be the epic rant/expose on that terrible situation almost a year ago (i wouldn’t want to soil the mood with that sordid affair). Luckily, a recent article by good ol’ Brian Switek gave me an idea.

The giant tantrum thrown by the dinosaur fanboys over the upcoming film Jurassic World also played a role. I’d say it’s all been rather pathetic (one guy on Facebook seems to have what can only be called a personal vendetta against the movie) and short sighted. Dinosaurs overwhelmingly dominate all things prehistoric. Movies, books, tv, documentaries, and museum displays. People see giant skeletons they automatically assume it’s a dinosaur. Whenever I tell people I’m pursuing paleontology, they automatically assume it’s about dinosaurs. But it still doesn’t seem to be enough for the fanboys. They are getting another love letter to their beloved “terrible lizards” but it’s still not enough. I’ll save that for another post to avoid a ranting tangent. Point is, dinosaurs reign supreme in the public conscience.

But prehistory doesn’t begin and end with them. The period after the dinosaurs, the Cenozoic era, hosted (and continues to host) a staggering diversity of creatures equally as awesome. In fact, I’d go so far to say that many of the denizens of the Cenozoic are even more spectacular than dinosaurs. That’s just me, but hopefully you’ll understand why at the end of this post. Switek’s article was brief and only touched upon mammals. While mammals dominate the Cenozoic, they weren’t the only ones to experiment wildly with size, shape, and extreme adaptations. There are so many you could write a book about them. Hell, this post was originally supposed to contain 30 entries. But I had to cram in 5 more, and even then it was only achieved by making some of the entrants share slots. So without further ado, here is my list of 35 Cenozoic Creatures as Awesome as (or even more so than) as Dinosaurs.

1. Deinotherium

Proboscideans are among my favorite prehistoric animals. So let’s start off with one. Deinotherium was an oddball even compared to the elephants we’ll see later. T has a longer neck then you would expect. And it’s bloody big too. The largest species is a contender for one of the largest mammals ever. What? Oh right. Deinotherium is best known for its tusks. Many (if not most) ancient elephant lineages had lower tusks in addition to upper ones. But not only does Deinotherium lack upper tusks, but its lower tusks have grown down and back like a giant pair of fangs. This has lead to their unofficial nickname “hoe-tuskers”. But just how they were used is still a mystery. Did they use them to dig up roots and tubers? Were they used to pull and rip branches? Or were they used to strip bark from trees, the oldest of the hypotheses? Who knows if we’ll ever know, since there is nothing else like Deinotherium today or in the fossil record. So naturally that made it a great opener for a post like this.

A pair of Deinotherium wander through the forest of Miocene Europe. By my all time favorite paleo artist Mauricio Anton, from “National Geographic’s Prehistoric Mammals”

skeleton of Deinotherium at the Stuttgart Museum, Germany. From Wikipedia

Skull of Deinotherium giganteum at the Oxford Museum of Natural History. From Wikipedia

2. Amphicyon

Dogs are cool. So are bears. So you’d think a mashup of the too would be super cool. Well that is kind of what we have in Amhpicyon. It is the largest (and arguably the most successful, judging from its presence on 3 continents and nearly 8 million year existence) of the bear-dogs. They got that name because early scientists thought they were ancestral to both dogs and bears since they had traits of both. But we now know that dear-dogs were their own distinct group, the Amphicyonids. They have no modern descendants or close relatives. Apmphicyon was essentially the biggest carnivore of its time and place. It undoubtedly ate whatever it wanted. This obviously differed over its range. For example, study of a bonebed in Spain suggests one species regularly preyed on smaller fare like deer. The largest species, Amphicyon major, it’s estimated to have weigh over 600 pounds. All species, however big, possessed large skulls with powerful jaws and sharp canines. I think I’d want this guy on my side in a prehistoric bar fight!

Cast skeleton of Amphicyon at the Raymond Alf Museum of Paleontology.

A pair of Amphicyon major fight over a hot lunch in the middle Miocene wilds of Spain. By Mauricio Anton

3. Titanoboa

Funny story. When i was a kid we would go to brunch on mother’s day and then a movie afterwards. I am not exactly sure how, but we ended up going to see Anaconda. Because nothing says “celebrating motherhood” like watching people get eaten by a giant snake! The movie of course had to take liberties with the anaconda’s size so it could prey on humans. Anacondas are the heaviest snakes on earth; pythons are longer, but not as massive as anacondas. Estimating the size of anacondas is very difficult and so we don’t truly know how big they really get. Specimens over 20 feet long and weighing over 200 pounds have been reported. Now these snakes have been reported to attack humans (with a couple bodies being found bearings marks of the anaconda’s MO). While certainly capable of killing a human, they are unable to eat them. While anacondas can eat prey the size of a small deer, a capybara, or the smaller caimen species, these prey items are all somewhat narrow. Even the extraordinary flexing and stretching of a large snake skull can’t hope to get around a human’s broad shoulders (I had heard it hypothesized that a monster snake could swallow a human if they repositioned so that the shoulders are vertical, not horizontal. But even that seems like a stretch. No pun intended).

I tell you all this because even bigger snakes have been found in the fossil record. Wonambi of the Australian Pleistocene is the usual reference, but at 15-18 feet it is no bigger than a modern rock python. Go back further to the Pliocene and we find Australia’s true monster snake. Known as the Bluff Downs giant python, this snake is estimated to have measured 30 feet long and had the girth of a dinner plate. But fossils from the Eocene of Egypt hinted at an even bigger serpent. This snake is estimated to have stretched to 36 feet long. For a while this snake (Gigantophis) was the record holder. That is, until 2004 when paleontologists began trolling the Paleocene rocks of a Columbian coal mine.

The scientists found huge turtles, a wide array of crocodiles, fish, leaves, fruits, and seeds galore- the remains of an entire ecosystem, rivers and rainforests teeming with life. But something was off. The kept turning up strange vertebra. They looked like snake vertebrae, but at over 5 inches across they were far bigger than any other snake vertebra known.

On the left is the vertebra of Titanoboa. On the left is a vertebra from a 17 foot anaconda. From the website of the Florida Museum of Natural History

The snake was christened Titanoboa, the largest snake that ever lived. Based on the fossils found, it is estimated that Titanoboa was 42 feet long and weigh as much as 1.2 tons. It would have been an unthinkable 3 feet across at its widest point. Truly a monstrous reptile. Study of the plants found alongside it revealed why Titanoboa and its fellow reptiles at Cerrejon got so big. During the Paleocene global temperature was much higher than it is today. To give you an idea of how high, check out this lush forest:

A hippo-like pantodont feeds in an Eocene swamp. Taken from the exhibit “Extreme Mammals”

That is Elesmere Island. Of the coast of Greenland. Well above the arctic circle! The tropics (where Columbia resides) are notorious for being hot and humid today. Well it was even more so ~60 million years ago. Reptiles are ectotherms, meaning their body temperature is dictated by their surroundings. Large reptiles need a constantly warm environment or they will freeze to death. Since it was insanely warm during the Paleocene, this allowed reptiles to go supersize. One turtle from Cerrejon had a shell 6 feet long and over 3 feet wide- about the size of a pool table!

Shell of the giant snapping turtle Carbonemys coffrinii. From the website of the Florida Museum of Natural History

Titanoboa was undoubtedly a top predator. What did it eat? There were 6 foot lung fish for starters. There were many crocodiles, ranging from 6 to 22 feet. Most turtles may have been too wide even for Titanoboa to swallow (although smaller juveniles would certainly be fair game). Like it’s modern cousin the anaconda, Titanoboa probably spent most of its time in the water. It’s bulk made it slow and awkward on land; but the water, able to support it’s great weight, allowed Titanoboa to move quicker and more fluid. In a world overrun with giant reptiles, Titanoboa stood out as a terrifying, colossal monster. Clearly it reigned over the ancient Cerrejon ecosystem, unchallenged at the top of the food chain.

Fleshed out model of Titanoboa devouring a crocodile (with puny humans for scale). By Getty Images, from Wired.com

Or maybe not. Tantalizing evidence hints at another gigantic cold blooded terror prowling the ancient rivers. Remember that six foot turtle shell? You’d think something like that would be relatively invulnerable to predators. But lo and behold:

Bite marks on the shell of a giant turtle. From “Titanoboa: Monster Snake” by the Smithsonian Channel

Even the largest croc known from the site couldn’t have made bite marks like that. What could have? A partial vertebra sheds some light:

Partial vertebrae of a giant crocodile. From “Titanoboa: Monster Snake” by the Smithsonian Channel

Partial vertebrae of a giant crocodile compared to the vertebra of a saltwater crocodile, the largest extant crocodilian. From “Titanoboa: Monster Snake” by the Smithsonian Channel

Based on comparison with other crocs, it is estimated the Cerrejon specimen came from an animal 40 feet long. That’s almost as long as Titanoboa (and undoubtedly much heavier)! As if a giant snake isn’t bad enough, we have a giant crocodile as well. And not only that, but multiple giant crocodilians!

4. Purussaurus

There must have been something in the water of prehistoric South America. Not only did it produce the largest snake ever to live, but also the largest freshwater turtle to ever live (Stupendemys, with a shell 8 feet long). And it has also produced two contenders for largest crocodilians of all time. We already met one (the Cerrejon mystery giant). But much later in prehistory did another juggernaut would vie for the title. It is called Purussaurus.

“Om nom nom!” from Dinopedia

Purussaurus has been found in Peru, Venezuela, and possibly Brazil. It is thought to be related to alligators and caimans, based upon it’s short rounded snout and other features. Measurements of fossils peg Purussaurus at over 40 feet long. Biomechanical studies indicate it do the “death roll”. This is a technique used by modern crocodilians to subdue and dismember their prey. And when your head is this big:

Cast skull of Purussaurus at the Raymond Alf Museum of Paleontology.

There was virtually nothing this guy couldn’t consider food. The Amazon and it’s tributaries are already considered incredibly dangerous because of all the critters that could kill you. If Purussaurus were still alive today, it would render any river goer petrified with fear.

Life-size model of Purussaurus at a museum in Peru. By deviant art user Pyroraptor42

5. Thylacosmilus

Yet another overlooked but marvelous South American native is Thylacosmilus, the “marsupial” sabertooth. Dinosaurs are always trumpeted as marvels of evolution. But I think the Cenozoic era provides the strongest examples of various evolutionary phenomena. For example, convergent evolution. Convergent evolution posits that animals lving in different parts of the world will evolve similar traits to fill similar niches. And you couldn’t ask for a better example than Thylacosmilus. It looks so much like a sabertooth cat. If you showed it to any lay person (and probably many scientists), they would think it was a sabertooth cat. But it wasn’t.

For most of the Cenozoic era, South America was an island continent, cut off from the rest of the world. The animals there evolved in complete isolation, This allowed many primitive orders of animals to fill the ecological roles occupied elsewhere by more familiar species. Dogs, cats, bears, nimravids, and other carnivores were absent in South Ameica. So several groups of primitive mammals called metatherians rose to the challenge. Thylacosmilus belongs to a group called thylacosmilids. These animals filled the niche occupied elswhere by sabertooth nimravids and true cats.

Skull of the sabertooth ripoff Thylacosmilus. From Wikimedia.

Originally, these primitive carnivores were thought to be marsupials. But more recently they have been given their own families inside the larger group Metatheria. This has really been itching my brain. Marsupials are famous for reproducing via a pouch. Did metatherians (which marsupials belong to) also reproduce this way? Because Thylacosmilus means “pouched knife”. It would be a little awkward to keep a name like that and not actually be applicable.

Fleshed out reconstruction of Thylacosmilus. By Mauricio Anton, from “The Big Cats and Their Fossil Relatives”

Thylacosmilus was the last and largest of the Thylacosmilids. It died out ~4 million years ago. It is thought that competition from more advanced placental carnivores drove these archaic predators to extinction. But before then, Thylacosmilus undoubtedly reigned supreme. It was short and stocky, like many sabertooth predators. But it walked on the flats of its feet, unlike true cats that walk on their toes. This means thylacosmilus was an ambush predator, using surprie and power in place of speed. Just like most sabertooths are thought to do. Thylacosmilus may have been a fake sabertooth, be he was a damn good fake.

6. Megalania*

Another record breaking reptile. While debate goes on over just how big it was, fossils show that it was much bigger than the largest giving lizard, the komodo dragon. Estimates by Ralph Molnar place Megalania at ~18 feet long an ranging from 600-1000 pounds. Of course these are just estimates. The number of Megalania fossils known number in the double digits. The paucity of fossils have made study of its life and evolution quite difficult. But if it was anything like the komodo dragon, than Megalania was certainly a top predator. There was probably nothing it couldn’t tackle, although the 3 ton Diprotodon may have been too much even for it. It has been suggested by some that Megalania may have been venomous like komodo dragons. However, there is no way at present to determine this.

Reconstructed skeleton of Megalania assembled by Gondwana Studios.

Megalania appears to have died out with the rest of the Australian megafauna between 40,000 and 50,000 years ago. This is suggested to have overlapped with the first humans to have entered the continent. Titanoboa, Purusaurus, and the dinosaurs all died out long before hominins walked the earth. But Megalania was around when humans were. It must have been a terrifying sight to the first Aborigines. Humanity at that point likely had experience with lizards a few feet long tops. But now they were confronted with a beast the size of a grizzly bear. Given these early people were armed only with spears and javelins (both probably consisting of sharpened sticks with fire hardened tips), Megalania must have been a worthy adversary.

A scene set in the Pleistocene of Australia. One Megalania feeds on the carcass of the rhino-size marsupial Diprotodon. Another Megalania, perhaps attracted by the smell of the kill (or carrion) approaches from the left. By one of my favorite paleoartists Mark Hallet. Used as the cover for “Dragons in the Dust: the Paleobiology of the Extinct Lizard Megalania” by Ralph Molnar.

In my post about Megalania, I alluded to a study by an anthropologist who thinks Megalania may have survived into the Holocene. They base this idea on analysis of a legend told by a tribe of southwest Australia. This sort of thing is exceptionally hard to prove, especially since science pays no heed to anecdotal evidence. But it may be equally hard to disprove, since Australia’s poor fossil record (compared to other continents at least) has provided so few fossils of Megalania and dingoes. It seems this awesome predator has many secrets yet to be revealed.

*(yes, I’m using the old name Megalania, even though it was officially changed to Varanis priscus. Ralph Molnar in his book said Megalania would probably live on as the common name. So that is what I’m doing. Because a name that translates to “giant ripper” is too awesome to let fall by the wayside. Besides, if Brian Switek can attempt to make the nickname “shovel-beaked” a thing, then I reserve the right to try to make Megalania the all too apt nickname of this “true dragon of the past”.)

7. Procoptodon

Kangaroos are the pretty much the official symbol of Australia. They are a ubiquitous feature of the landscape And at 150 pounds, the red kangaroo is the largest living marsupial. But not so long ago there was a kangaroo that put the modern champ to shame. Called Procoptodon goliah, it was the biggest kangaroo known. Standing 7-7 1/2 feet tall and weighing 400 pounds, it was a giant among marsupials. But size alone doesn’t set Procoptodon apart from the rest. It was part of an extinct subfamily of kangaroos called sthenurines. A trademark of these kangaroos was a short face. Procoptodon’s skull looks like a red kangaroo smashed into a wall cartoon style. The short deep skull facilitated powerful chewing muscles, a trait needed to process Australia’s rough forage.

Skull of Procoptodon goliah

Sthenurines were also very robust. Their bones are much thicker and heavier in appearance when compared to their more gracile cousins. These animals also possessed a single toe on each foot; in the case of Procoptodon, a large thick claw. It is debatable whether they were as fast as modern kangaroos. Though being browswers, they probably lived in more wooded habitats where speed isn’t as important. Speaking of browsing, sthenurines were capable of reaching up over their heads. They probably used their large claws to hook down branches to get at the leaves. Procoptodon was capable of reaching 9 feet up to grab lunch. It is because of this supposed feeding habit that I think the sthenurines were the Australian equivalent of ground sloths. Sloths are the closest fit, but basically they were the high reaching browsers; the same niche filled elsewhere by camels, giraffes, and deer. A critter further down the list has been suggested as being a ground sloth analogue, but I think these extinct kangaroos are a better fit.

Life rconstruction of Procoptodon goliah. From National Geographic

Like the rest of the Australian megafauna, Procoptodon is thought to have died out 40,000-50,000 years ago. Whether it was overhunted by humans or wiped out but by climate change is yet to be determined. What a loss I say. Australia’s deep past has always fascinated me. It reached its climax in the Pleistocene, with a fauna unlike anything in the world, before or since. I hope I have you hooked because you’ll be seeing plenty more of them.

8. Kelenken

I can hear the dino fan boys now.”You said you weren’t doing dinosaurs. Birds are dinosaurs! Haha, you can’t escape their awesomeness!!!1!”. Look, I won’t dispute the fact that birds are descended from dinosaurs. But I will never see birds proper as dinosaurs. I understand the joy and satisfaction you get in knowing that all those feathered things flitting around the park or your backyard are a physical connection to your favorite prehistoric animals. But does everything have to be about dinosaurs? Can’t a bird be a bird? To me, there is still a gulf of difference between this:

Great blue heron. Image from Wikipedia

And this:

Oviraptorosaur from the late cretaceous of North America. Art by Dr. Julius Csotonyi

Birds are a highly diverse, highly successful class of vertebrates. Apparently that means nothing unless we are constantly reminded that they are dinosaurs. Because dinosaurs are the COOLEST THINGS EVER!!! So yes it is technically a dinosaur, but kindly shut the fuck up about it while I talk about a bird that would make Alfred Hitchcock shit his pants.

As I said above South America was cut off from the rest of the world. While many distinct groups evolved to fill the niches fill elsewhere by more advance mammals, perhaps the most curious case is the large carnivore guild. We saw one side of this coin with the metatherian mammals. But the other side of that coin is what usually gets the attention. While the carnivore guilds of the world were dominated by mammals, South America’s landscapes were terrorized by birds.

Phorusrhacids of different sizes and bilds. By Alvarenga and Hoefling

The group is called the phorusrachids, commonly referred as “terror birds”. These flightless birds appeared in the Eocene epoch and survived until the late Pleistocene. They ranged in size from a stork to Brontornis (“thunder bird”), who towered 9 feet tall and weighed 700 pounds. I chose to do this guy because he’s relatively new and is one of the larger examples. The name Kelenken comes from a god of the local Native Americans where the remains were found (in Argentina, which I am now convinced has the best studied record on the continent). An apt name for a bird with a skull 28 inches long (the size of a horse’s). Also found was a partial foot bone. This foot bone allowed scientists to estimate its size. At 7 feet tall and 400 pounds, Kelenken is one of the larger members of the phorusrachidae.

Well the photo speaks for itself.

Kelenken was clearly a top predator, but how it dispatched prey is still a mystery. A relative, Andalgalornis, was estimated to run over 40 miles an hour. This hypothesis was reached by studying its surprisingly muscular legs. This would make it the fastest known biped. But the authors favored an alternative hypothesis: that Andalgalornis used its strong legs not to run fast, but to utilize a powerful stomp. This may have been to break open bones to access the nutritious marrow; or it may have been used to kill prey like a modern secretary bird. Keleken may have used a similar kick to kill prey. Or it may have used its strong sharp beak to jab at hapless victims. A National Geographic (before it became the crime channel) documentary suggested it may have been able to prey on the smaller species of glyptodonts by flipping them over and tearing at their vulnerable underbelly. Without more fossils of the predator and prey it’s impossible to say for certain.

A phorusrhacid tells a group of borhyaenids that this kill is taken.

Terror birds were thought to go extinct at the beginning of the Pleistocene. The cause, according to the hypothesis, was competition from mammalian carnivores. But it doesn’t look that simple. For starters, one species of terror bird called Titanis actually came north into the southeast United States and stuck around for 3.1 million years, amidst all the supposedly superior predacious mammals. Also, a fragment of foot bone of a phorusrachid found in Uruguay dates to just 40,000 years ago. Again, amongst all the “superior” mammalian predators. Was it differences in habitat, diet, or something else? There is a lot more that needs to be done on the terrifying terror birds and the strange world they lived in.

The end of the terror birds? By deviant artist Egan7

9. Odobenocetops

Convergent evolution can cause strange things to occur. So far we have seen a sabertooth cat that wasn’t, birds and lizards as top predators, and giant kangaroos. Now we come to yet another oddball born of the need to fill a niche in his own neck of the woods. During the Pliocene the marine mammal world saw the emergence of the earliest true walruses. What is not to love about walruses? They have a funny name, they make funny sounds, and they just look funny. Their most conspicuous feature is their two long tusks. Males are the ones with the long tusks, which they use to fight rivals; both sexes use their tusks to defend themselves from predators and to hook themselves up onto ice flows. Walruses are perhaps the strangest beasts of the arctic. So tell me: what happens when a dolphin tries to be a walrus?

You get Odobenocetops. This weirdo lived along the coast of Peru ~4 million years ago. The name is translated as “whale that walks on its teeth”. The walrus’s name is Odobenis, which means “tooth walker”. I doubt the name similarity is a coincidence. Anyway this guy is so weird he is placed in his own family, the Odobenocetopsidae. As if a tusked dolphin wasn’t odd enough, Odobenocetops took the weird factor to another level. Females sported tusks one foot long. The males, however, rocked one tusk a foot long and the other tusk three feet long. It is though males used their tusks to spar with each other, much like walruses do. I’m sensing a theme here…

Cast skull of Odobenocetops at the Natural History Museum of Los Angeles County

Odobenocetops lived in the warm shallow waters of a coastal ecosystem. It is thought to have vacuumed up mollusks from the sea floor. It would then use its tongue like a piston to suck the tasty invertebrates out of their shells. This feeding style is based on the fact that Odobenocetops possesses a strongly arched palette combined with a total lack of teeth (save for the tusks). How do those features suggest suction feeding? I’ll give you one guess. That’s right. It’s the same equipment used by walruses to suction feed on clams and other shellfish. Odobenocetops was a dolphin everywhere on its body… except its head, where it was a walrus.

Two male and one female Odobenocetops. From Wikipedia

Not to steal the “walrus dolphin’s” thunder, but he shared his habitat with another complete weirdo. It was called Thallasocnus. It was a ground sloth, an animal usually thought of as slowly pondering around on land. But Thallasocnus was an aquatic ground sloth. Its remains have been found exclusively in marine deposits, the same deposits as Odobenocetops, sharks, and other whales. Modern tree sloths are actually pretty good swimmers, which I guess must be a prerequisite when you live in a forest that annually floods. Scary looking marine reptiles of the Mesozoic capture the imagination of most people. But I would give anything to have seen The Aqua Sloth swimming in the sea.

10. The Tuskers

Prehistoric elephants are among my absolute favorite denizens of the fossil record. They have a fascinating, storied history, spanning 45 million years. They journeyed far and wide, becoming prominent members of any ecosystem the settled in. Majestic and grand, their remains dominate most Cenozoic halls. Mammoths and mastodons are the most commonly seen in museums. But during the Miocene there was a diverse group called Gomphotheres. Within this group there was a family affectionately dubbed “shovel-tuskers”.

Fossils of the shovel-tuskers started popping up in the late 19^th/early 20^th centuries as the American west was tossed and tumbled by paleontologists. But shovel-tuskers didn’t really enter the limelight until the 1920s. Among the many great finds of Roy Chapman Andrews’ Mongolian expeditions was a shovel-tusker bonebed. The remains belonged to Platybelodon:

Skull and lower jaw of Platybelodon. Image from Wikipedia.

A small herd of Platybelodon enjoying themselves along the banks of a Miocene river. By deviantart user MrsCoelodonta

Skulls and jaws of male (top) and female (bottom) Platybelodon from China. Note the broad nature of the tusks and jawbone symphisys. From Wang Shiqi et al, 2013

Andrews described the jaw of this animal as “resembling a great coal shovel… The jaw was five feet long. A truly stupendous organ”. And the analogy stuck.The scientific minds of the expedition, Henry Fairfield Osborn and Walter Granger even went so far as to include this image in their description of the fossils:

The lower jaw of Platybelodon compared to a shovel. From Osborn and Granger, 1932

Shovel-tuskers were viewed as using their jaws as scoops. What did they scoop? Well that’s harder to pin down. You see, there wasn’t a standard design. There were many variations:

Complete lower jaw of Amebelodon (from Florida, i believe). Image from Wikipedia.

Lower jaw of Amebelodon at the University of Nebraska State Museum. From “The Cellars of Time: Paleontology and Archaeology in Nebraska” by Voorhees et al

Lower jaw of Torynobelodon from Nebraska. From Barbour, 1931

Lower jaw of Torynobelodon compared to Platybelodon grangeri. From Barbour, 1931

Lower tusk of Torynobelodon. From Barbour, 1929

Purely conjectural reconstruction of the lower jaw of Torynobelodon, based on the curvature of the lower tusk. From Barbour, 1929

Hypothetical reconcostruction of Torynobelodon grubbing for water plants. From Barbour, 1929

Lower jaws of Serbelodon. From Osborn, 1933

Skull and jaw of Gomphotherium from northern California, on display at the Lawrence Hall of Science, UC Berkeley.

Lower jaw (front) and skull (back) of Tetrabelodon. Image from Wikipedia.

Lower jaw of Archaeobelodon from Europe. Image from Wikipedia.

Reconstruction of Stegotetrabelodon. It has a relatively short jaw with very long bottom tusks. By Mauricio Anton, from the book “Evolving Eden”

Complicating the matter is another subset: the spoonbill mastodons. These were shovel-tuskers who had no lower tusks. The flagship species is a somewhat enigmatic animal called Gnathobelodon:

Lower jaw of the spoonbill mastodon Gnathobelodon thorpi. From Barbour & Sternberg, 1935

Lower jaw and upper tusk of the spoonbill mastodon Gnathobelodon thorpi.

Reconstruction of the spoonbill mastodon Gnathobelodon thorpi scooping pondweed. From Barbour & Sternberg, 1935

Joining the spoonbill clan is Megabelodon:

Lower jaw of the spoonbill mastodon Megabelodon from Nebraska. From Barbour, 1934

Mounted skeleton of the spoonbill mastodon Megabelodon, apparently spooked by a sabertooth cat. From Barbour, 1934

Reconstruction of the spoonbill mastodon Megabelodon feeding on leaves and twigs. From Barbour, 1934

Next in the spoonbill parade is Eubelodon from Nebraska :

Skull of Eubelodon morrilli from the late Miocene of Nebraska. From the University of Nebraska Lincoln Libraries Image and Multimedia Collections.

Skull of Eubelodon morrilli from the late Miocene of Nebraska. From the University of Nebraska Lincoln Libraries Image and Multimedia Collections.

And Choerolophodon from the Aegean region:

Skull of the spoonbill mastodon Choerolophodon from the late Miocene of Greece. From Konidaris et al, 2014

The structure of Megabelodon’s jaw clearly indicates it evolved that way. But how do we know it wasn’t simply a pathology? That some traumatic injury caused it to lose the lower tusks and the bone grew back in a funky manner? A little thing called multiple specimens:

Lower jaws of different species of Megabelodon. The left specimen is from South Dakota, while the right is from Nebraska. Barbour, 1934

Skull and jaw of Megabelodon (i believe the same one from Barbour’s paper) on display at the Geology Museum at the South Dakota School of Mines and Technology. Image by flickr user James

But of course, when dealing with such a large and diverse group, there’s bound to be at least one outlier. Enter this gomphothere on display at the Denver Museum of Nature and Science:

Skeleton of a gomphothere with a peculiarity in its lower jaw. From flickr user James Brian Clark.

A pdf about the history called it “Amebelodon phippsi”. However, i contacted the museum and was told it was reclassified as Gomphotherium productum. There is one problem however: it doesn’t have any lower tusks. All the images of Gomphotherium productum i can find clearly show tusks in the lower jaw. Was this specimen just found without the lower jaws? Or were they never there to begin with? The jaw appears to be symmetrical, which rules out pathology. Could it be that this is another specimen of Megabelodon? It does bear some similarities to the jaws we saw above.

Anyway, just what were shovel-tuskers doing with their jaws? The traditional view was that they used their tusks to either dredge water plants or dig up roots. I once heard it suggested that Gnathobelodon scooped aquatic plants while the shovel-tuskers, with their solid lower tusks, “attacked firmer soil”. The hypothesis for Megabelodon (at least the “main” specimen from Nebraska) was that the end of the lower jaw supported a thick gristly pad that may have been used to grab leaves and twigs. Some work has been done on Platybelodon and Amebelodon. The study looked at the wear on the lower tusks and found that rather than plowing wetlands for lunch, they may have been using their tusks to cut grass and peel bark from trees. Perhaps their tusks were Swiss army knives, used for a variety of functions. More study is needed.

For example, i think paleoenvironmental data should be taken into consideration. Microwear analysis of the teeth of Choerolophodon suggested it lived in an open, arid habitat. At the same time shovel-tuskers of the genus Gomphotherium lived in the wetter and more forested lands of Germany. Neither invaded the others range.  Eubelodon lived at a time when the vast sea of grass known as the Great Plains were taking hold. Perhaps the loss of tusks and shortening of the jaw were a response to dwindling forests and decreasing water sources. Maybe some of the shovel-tuskers did use their jaws on trees in some way. This in turn could be why they mostly went extinct by the late Miocene. The riddle of the shovel-tuskers has yet to be solved. Chief among the questions is: if these tusk and jaw arrangements evolved to browse leaves and cut grass, why the elaborate set up? Mammoths, mastodons, and modern elephants were/are able to feed on these food sources with just their trunks. Since the ancestors of these animals already had somewhat elongated jaws with lower tusks, did they just end up developing what they already had? So as you can see, a lot of work remains to be done. Truth be told I don’t know why more people aren’t studying these truly awesome and fascinating animals.

11. Sabertooth Salmon

Saber teeth have been found in four groups of mammals: creodonts, nimravids, thylacosmilids, and true cats. Saber like teeth are also known in gorgonopsids, ancient mammal-like reptiles. But the Cenozoic found yet another group to slap these stunning teeth on: salmon. Salmon are perhaps the best known food fish. They are also well known for their lifestyle. Salmon live in the sea but return to freshwater streams and rivers to spawn (the same one where they themselves were born).

Oncorhynchus rastrosus was undoubtedly the king of salmon. It grew to 9 feet long. So not only did it sport the characteristic saber teeth, but it was pretty big as well. I wish I could say more, but fish are outside my area of “expertise”

12. Gigantopithecus

King Kong is my all time favorite movie. Which one you may ask? Both of them. I don’t try to argue which one is better. They both serve different purposes, have different methods of conveying their themes, and are both reflections of their times. The ‘76 version just sucked ass. Needless to say I am looking forward to Legendary’s “Skull Island”, although I not entirely sold on setting it in the 1970s. I feel having it set in the ‘30s added to the sense of adventure and to the challenge of combating giant prehistoric monsters. Look no further than the climax of the ’76 version. Instead of a fierce and thrilling battle atop the Empire State Building, Kong was dully gunned down by helicopters armed with mini-guns. Does Skull Island seems as frightening and foreboding if your men are armed with assault rifles, modern hand grenades, and machine guns? I don’t think so. But we will have to wait and see what the film makers have planned.

BOO! Watching helicopters sit there and pump Kong full of lead is boring! Copyright Paramount Pictures.

Kong is usually thought of as pure fantasy. But the fossil record, as usual, shows fact is stranger than fiction. In 1935 a German scientist bought a fossil tooth in a Chinese apothecary. The Chinese believe fossils to be the bones of dragons and as such grind them up for medicinal purposes. The tooth proved to be that of an ape. Based on the size of the tooth, it must have been one huge ape. He named it Gigantopithecus blacki, the “gigantic ape”. Since that initial discovery 3 lower jaws and 1300 teeth have been found and that is why Gigantopithecus is such a mystery.

Life sized model of Gigantopithecus on display at the San Diego Museum of Man

Cast of the lower jaw of Gigantopithecus, with my pocket knife (5 inches closed) for scale. Taken at the San Diego Museum of Man

Teeth and jaws can be helpful in understanding taxonomy and diet, but little else. Not even a partial skull has turned up. So we have to make do with what we have. Based on the dimensions of the jaws, it is estimated (key word being estimated) that Gigantopithecus would have stood 6 feet tall on all fours, 9 feet tall on its hind legs, and weighed 1100 pounds. This makes Gigantopithecus the largest ape and largest primate by far. Of course without postcranial bones this size estimate is far from perfect. The large, robust teeth suggest it ate very tough vegetation; bamboo has been suggested as a staple. It was obviously too heavy to live in the trees and would have had to live on the ground. Without any limb and foot bones we have no idea how it walked. Anthropologist Jeff Meldrum has suggested that Gigantopithecus was bipedal since the classic ape knuckle walk would not work with an animal of that size. This is often brushed off as preposterous and just another hair brained idea to support his belief in Bigfoot. But how do you know? Some modern great apes knuckle walk, but they don’t even approach Gigantopithecus in size. It was over 7 times the weight of a chimpanzee and almost 3 times heavier than a gorilla. Many species of ground sloths equaled and exceeded the weight of Gigantopithecus, but they aren’t built like apes. The knuckle walking Chalicotherium was twice the weight, but does it serve as an appropriate analogue? Again, without any bones of the limbs and hands/feet, how Gigantopithecus got around will perhaps be the biggest enigma of all.

Dating Gigantopithecus has been difficult as well. Right now the youngest dates for the big ape are a little as 100,000 years ago. This would seem to overlap with the early human Homo erectus. Did they cross paths? Hard to say. Gigantopithecus kinda just disappears from the fossil record. Did Homo erectus have a hand in its extinction? Or was it competition from early pandas over access to bamboo? It seems we know more about King Kong than the real McCoy.

13. Deaodon

Predatory dinosaurs get all the hype. Jack Horner once said in a discussion at the Natural History Museum in London: “I’d rather be locked in a room with 4 lions and a tiger than one little Velociraptor. Because that Velociraptor will probably eat half of me before it kills me.” Evidence? Why Jurassic Park of course (ok he didn’t say that explicitly, but seriously, where else could such hyperbole come from?)! In the film series Velociraptors are huge, super fast, hyper intelligent killing machines that can eat a cow in 10 seconds and run as fast as a cheetah and leap 15 feet into the air and be lethal at 8 months old and AAAAAAAHHHHHHH!!!1! If only. Never mind the fact that I could take out the real Velociraptor with my pocket knife; dinosaur behavior is a very hard nut to crack. Even more difficult is saying with any certainty if they were as savage as their Hollywood counterparts. There is evidence that T. rex was pretty nasty, but raptors are harder to come by. So let’s meet an animal who was every bit the tyrant people think Velociraptor was: The Hell Pig.

The official name is Entelodont. These animals are called pigs, are related to pigs, but are their own distinct group. Entelodonts lived from the latest Eocene through to the early Miocene. Their fossils are known from Europe, Asia, and especially North America. They were very robust, not particulary fast (due to the fused nature of their lower legs). These animals were built for power. They possessed huge heads with massive jaws and teeth. And those skulls are how we know they were so vicious. Many entelodont skulls have been found with fractures and bite marks. Aside from matching up the bite marks, the only animal alive at the time place that could do that kind of damage to an entelodont… was another entelodont. Looking at the skull it is easy to see it was built to savage and get savaged back. The canines are thick and robust. The flaring cheek bones likely helped to project the eyes. Their modern relatives, the pigs are similarly equipped. The wide cheek bones and various warty calluses- the things people think make them ugly- help protect their eyes and faces when males fight each other. Hey whatever gets the job done.

The entolodont Archaeotherium scares away a pair of the primitive dog Hesperocyon from a watering hole. Oligocene of western North America. By Mauricio Anton from the book “National Geographic: Prehistoric Mammals”

Now onto the star: Daeodon. This guy was the largest of the Entelodonts. It stood 6 feet tall and weighed as much as a modern bison.

Daeodon compared to a carnivorous dinosaur. While most people would think the dinosaur would win, it’s really anyone’s guess (entelodonts certainly have the jaw power and attitude to give dinosaurs it’s size a run for their money). From the Carnivora Forum

Its massive skull was almost 3 feet long. The size of many tyrannosaur skulls (and only 1 foot shorter than the average T. rex skull).

The massive skull of Daeodon on display at the Carnegie Museum of Natural History. Image from Wikipedia.

The teeth are monstrous. In fact Daeodon means “dreadful teeth”. And bones of the contemporary herbivores show just how dreadful they were. The classic example is a humerus (upper arm bone) of a calichothere from the Agate Springs area in Nebraska, representing the bottom half of the bone. It bears several bite marks that match the teeth of Daeodon. Not only that, but the bone was bitten in half. We’re talking about an animal the size of a horse. And its bone was bitten in half.

Humerus of the calichothere Moropus that was bitten in half by a large carnivore. The marks are a great match for the tooth of Daeodon. Photo by Alton Dooley.

Whether it was killed or scavenged may be a moot point. Daeodon was big enough, powerful enough, and probably fast enough to dine on whatever it wanted. Entelodonts may have been like some bears today, using their size and strength to steal kills from other carnivores. While thought to be primarily carnivores, the heavily worn teeth of entelodonts show they ate just about anything they could get a hold of. They had the teeth and the jaw power to kill, crush, break, and grind. How many dinosaurs can claim that?

Fleshed out model of Daeodon on display at the Denver Museum of Nature and Science. Picture by Flickr User Michael.

Daeodon was not only the largest entelodont but it was also the last. It appears super sizing didn’t work out for them in the long run. Whether it was competition from new predators like bear-dogs and true dogs or climate change, one of the nastiest brutes to ever walk the earth had bitten one last thing: the dust.

14. The Giant Ground Sloth

Giant ground sloth is a common name seen in discussions about the Pleistocene. But the name really only applies to a few species. This next animal is not only giant in stature, but also the original giant prehistoric beast. At about the same time mammoths were being pulled from the Siberian permafrost a very different extinct giant was found in Argentina. It was unlike anything known at the time. To early naturalists, it looked out of this world. Here they had an animal with a wide pelvis even for a creature of that size. The rib cage flared out at the bottom to house a large gut. It had long arms and stout legs. It walked on its knuckles and the sides of its feet to protect enormous claws. The skeleton showed it could rear up on its hind legs like a bear. Its teeth have no enamel, so they were forever growing. A great trough in the lower jaw suggests it had a long tongue like a giraffe. Even to this day this animal and it’s kin are some of the strangest animals that ever lived on this planet.

This animal is Megatherium; the “giant beast”. Back before dinosaurs stole the spotlight, Megatherium and other Pleistocene wierdos from South America dominated museums and depictions of the prehistoric past. Skeletons of Megatherium and Glyptodon were the centerpieces of the most prestigious institutions in Europe. People marveled at this strange monster that towered over them. Scientists deduced that it was related to modern tree sloths. Though just looking at it no one could make that connection. Megatherium even factored into Charles Darwin’s theory of evolution. Looking at the fossils of this giant sloth compared to its living cousins helped illustrate extinction, that one species dies out while another related species lived on. But Megatherium’s days were numbered. Once dinosaurs started emerging as skeletons, the giant mammals of the past were overshadowed. It was all about who was bigger, scarier, toothier… Mammals having to play second fiddle to dinosaurs remains to this day.

Skeleton of Megatherium americanum stands tall and proud in the Natural History Museum, London. From Wikipedia

Megatherium lives up to its common and scientific names. Weighing five tons and able to stand 13 feet tall it was one of the largest species in Pleistocene South America. Megatherium always appears in depictions of the time. Usually it is shown resting on its haunches, pulling down branches with its claws and feeding with a long tongue (though I have heard somewhere that the tongue thing may not hold much water). Megatherium lived mostly in South America. I have heard a few reports in Central America. But there is one report that has caught my attention. According to Berkeley’s online database, there a vertebra from the Pleistocene of Santa Barbara County. The id: Megatherium sp. This could be big. This could greatly extend the range of Megatherium, showing it made it into North America along with other megafauna from the south. Hell, THE giant ground may have lived on the Central Coast! But we may never know though, at least for a while. I thought the vertebra might be a good first research project for me. So I wrote to Berkeley, even asking if they could send me a photo of the specimen, so I could determine whether or not I should drive 5 hours up there to investigate. I never heard back. I guess a prestigious institution such as Berkeley can’t be bothered with amateurs like me. Only “true” scientists allowed!

Ok, that’s a bit harsh. I of course have no idea why my efforts to contact Berkeley are a one way conversation. But it is frustrating when you are trying to make progress as an citizen scientist. And especially when you are trying to verify or debunk a potentially important fossil. And when that fossil concerns a species with a rich and intriguing history as Megatherium. Megatherium is every bit a cornerstone of the history of paleontology as Tyrannosaurus rex, Archaeopteryx, and Protoceratops. Perhaps I can help bring him back to his rightful glory.

A beautiful reconstruction of Megatherium (joined by the glyptodont Panocthus) on the pampas of Pleistocene South America. From the (ancient) Time-Life Nature Library: South America

15. Megalodon

Growing up, there were few things I loved watching more than those old dinosaur shows by Midwitch Entertainment. They were fun, well put together, and even informative now and then. But what stuck with me most was the music. While quite clearly 80s in style, they were nonetheless very evocative and really drew me in to the narrative. These qualities were perhaps most present in a song called “The Ice Age”. It was used to bring a particularly mysterious feel to the subject at hand (the woolly mammoth, Antarctic dinosaurs, and most fittingly, the Loch Ness Monster). I tell you this because this haunting tune enters my mind whenever I think about a shark that could bite Jaws clean in two. I’m of course talking about Megalodon.

This leviathan of prehistory almost needs no introduction. It has become so well known in recent years no thanks to modern B-movies and one truly dumbass Discovery Channel show (which purported to show Megalodon was still alive. It was a farce but because they presented it so seriously people actually believed it). But it has become one of the most famous mega-predators in prehistory. Despite all that has been written and done about Megalodon, we actually don’t know much about the animal proper. Being a shark it’s skeleton was composed of cartilage. Cartilage is softer than bone and thus never fossilizes (except under the most exceptional of circumstances). All we have are its teeth and a few vertebra. Sharks are contantly shedding and replacing their teeth. A single shark could go through up to 30,000 teeth in its life time. So luckily we have lots of Megalodon teeth to work with.

Teeth of Megalodon from southern California at the San Diego Natural History Museum

The teeth themselves are unholy in size. They average 5-6 inches long and are very thick for shark teeth. Looking at a Megalodon tooth, I am reminded of the sharktooth weaponry from the ancient Pacific. If Megalodon were still alive today, I can easily see those people using its teeth as spearheads and hand axes. But back on topic. Scientists have found a correlation between the size of a tooth and the size of the shark it came from. Using this formula, the best estimate for Megalodon is 50 feet long. The biggest killer shark today, the great white, rarely reaches 20 feet. I’ll let that sink in for a minute.

Life size model of Megalodon at the San Diego Natural History Museum. The model measures 34 feet long, a female according to them.

Given its great size Megalodon likely fed on large marine mammals. Whales appear to have been the main targets. Many a fossil whale bone has been found with bite marks consistent with Megalodon teeth. In fact some whale bones have been found with Megalodon teeth embedded in them. Now whales weren’t always the giants we know today. During the Miocene most measured 20-30 feet long. But when they started getting bigger in the Pliocene it appears Megalodon was able to keep pace. According to a National Geographic documentary, a whale found near Santa Barbara (Central Coast, yay!) had the tip of a Megalodon tooth in one of its bones. The hitch: this whale was the size of a modern fin whale, outweighing the mega-shark by 25 tons. Whether it killed or scavenged the whale is up for debate. There is no reason to think Megalodon was incapable of attacking a whale of this size.

A fossil whale rib bearing the tooth marks of Megalodon. In the old fossil halls at the Smithsonian’s National Museum of Natural History

Megalodon terrorized the seas for over 13 million years. There was nothing it couldn’t at least take a bite out of. So why did such an awesome predator die out? Current thought is it was a combination of climate change and prey. As the world’s oceans became cooler during the Pliocene Megalodon would have had to stay in warmer waters. Whales are thought to have adapted by developing their characteristic layers of blubber and migrating to colder waters. Without a consistent, year round food source, Megalodon starved into extinction. I’m pretty sure a lot of people, especially Jesse Cox, thank their lucky stars every day that the Godzilla of sharks is no longer with us.

16. Livyatan

For decades Megalodon was thought to be the undisputed king of the seas. It was perhaps the mightiest ocean predator that ever lived. Modern orcas are smaller and while able to prey on adult whales they need pack hunting behavior to achieve this. Sperm whales are the same size, but they only have lower teeth and feed on squid. The ancient whale Basilosaurus was as long but not as bulky, and probably didn’t tackle especially large prey (hell it was biggest animal on earth at the time). Megalodon was unchallenged. That is until 2008 when paleontologists in Peru found a whole new monster.

It was a whale, a sperm whale in fact. But it wasn’t like its modern cousin. Its 9 foot skull was much more robust. Not only were its teeth much more massive, but it had upper and lower teeth. This wasn’t some oversized squid sucker. This thing meant business. The scientists were Herman Melville fans and decided there was only one name worthy of this beast: Leviathan melvillei. Leviathan is not only a name of a Melville novel, and is not only a commonly used descriptor for giant marine monsters, but is also the name of a legendary monster in the Old Testament. Leviathan was lord of the seas and was the most feared creature in creation. Its immense size meant nothing was safe from its rapacious appetite. What better name for a whale like this? Unfortunately, the name didn’t last. Turns out some guy in the 19^th century used the name Leviathan on a mastodon tooth. So the authors had to change the name to Levyatan (the original Hebrew spelling). This is one of those instances where I feel the rules of science can just go eat a dick. The name was used on something that already had a name therefore it has to stick and cannot be used ever again. Leviathan was a much better name, so much more fitting. But that is just my opinion.

Reconstructed skull of Livyatan melvillei. By deviantart user Juandarkgraff

Livyatan is thought to have been a top predator. In fact many of the sperm whales during the Miocene were thought to be “raptorial” macropredators. These Miocene sperm whales had functional upper and lower teeth, which makes scientists think they were preying on stuff beefier than squid and fish. They were probably feeding on marine mammals in addition to large fish like modern orcas. There were many species of dolphins, pinnipeds, and sea cows to choose from. They may have even preyed on juvenile whales, or maybe even hunted cooperatively to take on adult whales. While all this is up for debate, we know it certainly had the hardware to do so. A study found that in addition to functional upper teeth and powerful jaws, these ancient sperm whales (or at least the species studied, including Livyatan) had unique knobs in their upper jaw. Analysis of these growths shows they would have acted as buttresses to reinforce the jaw; reinforced specifically during a strong up/down action. In this case, the high forces produced by a powerful bite. It should be pretty obvious that these whales were preying on things that required enormous bite force to subdue.

Skull of the sperm whale Acrophyseter, highlighting the bony buttresses that reinforced its teeth. From Lambert et al, 2014

So we had 2 giant predators prowling the coast of South America 12-13 million years ago (the other being Megalodon). How they coexisted is yet to be determined. Right now we just have the one specimen. But right now that one specimen is enough to fire the imagination. This was potentially a contender for largest predator in the history of the planet. If I ever came face to face with the gaping, spike-toothed maw of a real life sea monster, I think I’ll take my chances with those cute little mosasaurs.

Livyatan in the process of attacking a baleen whale

17. Woolly Mammoth

When I was two, my family took a visit to the Royal British Columbia Museum in Canada. I immediately fell in love with their model of a woolly mammoth. We would see some of the museum, then go back to see the mammoth. We would see some more of the museum, then go back to see the mammoth. My parents inform me they only got me to leave by buying me a poster of the big lug, which is still on my wall to this day. It’s part of why I am who I am and why I pursue paleontology. I last saw him in 2006. He still remains the best prehistoric model I have ever seen. You can go into the next gallery and see bear and elk that don’t look any more lifelike.

No photo, not matter how beautiful and well taken, cannot match the awe and power of seeing this model in person. From Wikipedia

Woolly mammoths are among my top favorite prehistoric animals. So you may be a bit surprised to learn that I’m actually not writing anything about it. I love it dearly, but let’s face facts. The woolly mammoth is not only the face of the ice age but it is one of the very icons of prehistory. Entire books, documentaries, and articles have been written about it. Not to mention it appears in just about every discussion of the ice age. Thus there is nothing more I can really add. Which is good because we are only halfway through and anything that reduces the amount of typing I have to do is welcome!

18. Elasmotherium

While we are on the subject of woolly giants, let’s explore a far less known but perhaps stranger beast. Now the woolly rhino is often depicted alongside the all too familiar mammoth. This is the species Coelodonta antiques. Remains have been found all across northern Eurasia, including mummified remains in a Polish tar pit. But he was not the only rhino running around. There was another behemoth that was bigger in every way. We are talking about Elasmotherium.

I use behemoth a lot to describe big animals, but Elasmotherium is one of the ones actually deserving of that title. It rivaled elephants in size, standing 7 feet at the shoulder and tipping the scales at 4-5 tons. Only mammoths and a couple giant sloths were bigger. Elasmotherium is not only famous for its size.

Massive skeleton of Elasmotherium caucasicum in the Azov historical and archaeological and paleontological museum-reserve. From Wikipedia

To understand the second reason, we need to look at how rhino horns work. Rhino horns are not made of bone but are made of keratin. This is the same material as your fingernails. A rhino skull has a rough built up base of bone that serves as an anchor for the horn. This is how we can estimate the size of the horns on extinct rhino. We know Diceratherium has two small horns because its skull has two small bases. We know Aphelops had no horn because its skull doesn’t have a base. Elasmotherium is different matter.

You see, rhinoceros means “nose horn”. Most rhinos follow this rule. But Elasmotherium was a hipster. He didn’t want to be “mainstream” and follow the “crowd”. His horn wasn’t on his nose. It was on his head:

Skull and reconstructed horn of Elasmotherium at the Natural History Museum, London. From Wikipedia

We know this because the dome resembles the roughened base. This makes Elasmothering look like he’s wearing a helmet (or like a pachycephalosaur).

Skull of Elasmotherium, prominantly showing the bony dome that served as the base of the horn. From Wikipedia

Based on the size of the base, the horn must have been huge. Most estimates put the horn at 6 feet long. That would skewer any would be predator. But this is really all just a round-a-bout way of showing you that unicorns are real. Just instead of beautiful horses they were giant, hairy, probably smelly rhinos…

Life reconstruction of Elasmotherium. By deviant art user WillemSvdMerwe

19. Paraceratherium

People, it would appear, are easily cowed by size. They are only awed by the biggest; they only care about the biggest. We see this problem in the public perception of paleontology, where dinosaurs rule. To the public, dinosaurs represent the biggest, weirdest things in nature. It doesn’t help that in the public arena the most extreme mammals can barely compete with the most basic of dinosaurs. I have already talked about how mammals once ruled the museums. Here we will meet one of the most extreme mammals. It is extreme for how big it is. It was found when Roy Chapman Andrews and his crew were scouring the Gobi for fossil treasures. While talking with local tribesmen, they were told of a place where they could find bones “big as a man’s body”.

The bones belonged to a type of rhino. But it was bigger than any rhino known, including the aforementioned Elasmotherium. In fact, only mammoths were on the same scale. The called the animal… well its name is a little confusing. Throughout my life I have heard it referred to as Balucatherium, Indricatherium, and Paraceratherium. The last one seems to have stuck the most so we’ll go with that. Paraceratherium lived during the Oligocene epoch (and very earliest Miocene), 34-23 million years ago. It is mostly known from Mongolia, although some remains have been through ought Asia and even into Eastern Europe. It resembled a giant cross between a rhino and a giraffe.

Life-size model of Paraceratherium at the California Academy of Sciences

Paraceratherium is the largest land mammal known. It is estimated to have stood 17 feet at the shoulder and weighed between 15 and 20 tons. But these estimates are problematic due to a lack of complete specimens (Seems all the paleontology in Mongolia is completely fixated on the dinosaurs. Maybe that’s why Andrewsarcus is only known from a skull. No one is even looking for the rest). Now Paraceratherium seems like a lightweight compared to dinosaurs. But not only is size not everything, but have you ever stoped and wondered why mammals are not as big as dinosaurs? Someone in the Royal Tyrrell Museum’s speaker series has some ideas. I’ll just let her explain it:

(Paraceratherium skeleton at the Moscow Paleontological Museum. From flickr user cazfoto)

Basically nothing came close to Paraceratherium’s size until the mammoths of the Pleistocene. Now I don’t know what may have spurred their gigantism (I haven’t read Prothero’s book). Because of its record breaking status, Paraceratherium is perhaps doomed to be mentioned mostly in countdowns of extreme mammals.

A herd of Paraceratherium crosses the grasslands of Oligocene Mongolia. By Mauricio Anton, from “National Geographic: Prehistoric Mammals”

20. Palorchestes

Back to the Land of Oz for us. Remember way back when I mentioned something in the Australian Pleistocene that is often thought of as being a ground sloth analogue? I was reffereing to this guy: Palorchestes

When Palorchestes was first described by Richard Owen he thought it was a giant kangaroo. So he named it Palorchestes which means “great leaper”. But Palorchestes was far weirder than most kangaroos. Owen described the species from the Pleistocene, Palorchestes azael. We didn’t get our first good idea of what the hell it was until the discovery of the Alcoota bonebed. Alcoota dates to around 8 million years ago and in addition to fossils of giant wombat-like animals, huge birds, and crocodiles, scientists found fossils of a new species of Palorchestes. Dubbed Palorchestes painei, fossils included a complete (albeit crushed) skull. This skull didn’t look like any kangaroo skull. In fact, it looked more like a tapir.

Reconstruction of the pleistocene species Palorchestes azael. From

It is thought that Palorchestes had a tapir-like trunk because, like tapirs, it has a heavily retracted nasal cavity:

Reconstructed skull of Palorchestes azael.From Museum Victoria.

But that is where the tapir similarity ends. Palorchestes had very robust limbs like a bear, ending in long sharp slaws like those of a ground sloth. Palorchestes teeth showed it fed on very abrasive vegetation. In fact, those teeth combined with the claws and muscles has led paleontologist Tim Flannery to call them “tree wreckers”. Perhaps a big part of their diet was tree bark. While more fossils of both species (Especially the Pleistocene one), like all Australian megafauna there is so much we have to learn about one of the strangest chapters in the history of life. Australia has a very poor fossil record when compared to the rest of the world. It is thought that this is the case because unlike some of the well known, very fossiliferous localities around the world, Australia has undergone very little geologic upheaval. Not only are new sediments not being exposed by uplift, faulting, and erosion; but without runoff from mountains and hills little new sedimentation takes place. But what Australia has generously given us thus far is one of the most fascinating tales of evolution. Animals weird and bizarre even by the standards of the fossil record evolving in isolation to produce animals like no others. Palorchestes is one of the strangest, but it is by no means the only one.

21. Meiolania

The Pleistocene of Australia was once thought to be ruled by reptiles. In fact, scientist Stephen Wroe once described it as “a b-grade rerun of the Age of Reptiles”. We now know this isn’t true (not only that, but I think Cerrajon is a better candidate for that description), that the Australian Pleistocene was a unique mixture of mammals and reptiles that was unique in earth’s history. The “reptilian domination” focused mostly on predators. But there was another odd reptile who added another twist to the surreal fauna.

Meiolania was a giant tortoise who belonged to an extinct subfamily, the Meiolanidae. These turtles were first thought to have first appeared in the Oligocene in Australia. But then Meiolanids were discovered in Argentina, one of them dating to the Eocene. This suggests they occurred before the breakup of Gondwana when Australia and South America were still connected. Some specimens of this group have been found on islands like Vanuatu, Lord Howe Island, New Caledonia, and possibly Fiji. These animals must have arrived by rafting. Meilanids are characterized by their spiky heads and heavily armored tails.

Skeleton of Meiolania on display at the American Museum of Natural History. From Wikipedia

Rear view, offering a better look at the nasty looking tail club. From Wikimedia

Meiolania was the largest, stretching 8 feet long and probably weighed at least a ton. This makes it the second largest terrestrial turtle/tortoise (surpassed only by Megalochelys atlas). The horned skull and tail club feel reminiscent of the ankylosaurs. But with their domed shells and armored tails they remind me of South American glyptodonts. Now Meiolania wasn’t alone during the Pleistocene. In Queensland it was joined by its smaller cousin Ninjemys. And yes, that name means “ninja turtle” and yes it was meant to honor who you think it does. Like the glyptodonts they resemble, they were likely almost immune to attack from predators.

These giant tortoises succumbed to the same extinction that claimed Australia’s megafauna 50,000 years ago. The two sides butting heads are humans and climate change. Climate change posits that at this time there was a massive climate shift in Australia. The climate became hotter and drier. This wiped out the plants that the mega herbivores fed upon. Without mega herbivores to prey on the mega predators followed them into oblivion. Not so says the human crowd. They argue that it doesn’t make sense that these animals survived numerous climate changes before only to succumb to this one. They argue that over hunting by humans must have been the culprit. One study done on the fossil teeth of wombats and eggs of emus shows there was a huge crash in plant diversity. They argue that the abruptness can only be explained by human intervention. Humans are thought to have entered Australia ~50,000 years ago. The timing is suspicious but alone is not enough. It is argued that the sudden crash in plant diversity was caused by the Aboriginal practice of burning the bush. This is when the land is deliberately set on fire, not just to flush out game but to also make the land more suitable to the animals they like to hunt (this practice isn’t exclusively Australian). How can a population of 3 ton wombat-like animals (Diprotodon) hope to survive if humans are burning away their food?

The debate is fierce and there is no hope of it being resolved anytime soon. Too few sites that offer insight into this crucial time period have been uncovered. Was it just one factor or was it a combination of both? Whatever it was Meiolania managed to dodge it for a while. What are known as relict populations survived on the off shore islands. That is until they were settled by humans. Island ecosystems are especially vulnerable to change. With limited habitat supporting small populations and nowhere to run, it was easy for pioneering humans to wipe them out. In Vanuatu meiolanid bones have been found in a 3000 year old midden. It would have been fantastic if this lone survivor of the Pleistocene extinction had survived to modern day. Hell if any of the megafauna of Australia had survived. The wholly unique animals of Pleistocene Australia continue to call to me. While I wish the megafauna of the Americas had survived, Australia still captures my imagine the most. Perhaps if time travel is ever invented, and I could only go one place, it would the ice age in the strange and wonderful Land Down Under.

22. Kubanochoerus

Pigs are ubiquitous members of any farm. They not only make those funny oinking sounds, but also provide us with delicious bacon. Thanks to humans pigs span the globe. Many break free and become feral hogs, where they wreak havoc on the local ecosystem. In fact I have seen some people get surprised when I tell them pigs are not natives and instead are introduced invaders. Pigs are one of the ultimate survivors. They can and will eat anything, they reproduce like crazy, and are strong and fierce enough to live free from any natural predators. These pigs were in turn domesticated from wild boars, perhaps as early as 10,000 years ago.

So it should be no surprise then that pigs have a long and successful run through the fossil record. Of course back then there were large and powerful predators like sabertooth cats, bear-dogs, and hyenas that could take them (at least on occasion). Despite this pigs managed to create a diversity of forms. The strangest has to be Kubanochoerus gigas. Hailing from the Miocene of Asia, it was a hefty hog approaching the size of a cow. But it is most famous for the horn on its skull. This long horn is present only on the males, so it was probably used by males for fighting each other. So not only did rhinos try to be unicorns, but apparently pigs took a whack at it as well.

Skull and fleshed out reconstruction of Kubanochoerus gigas. By Mauricio Anton, from the book “Mammoths, Sabertooths, and Hominids”

23. Merycochoerus

The Cenozoic era is full of migration stories. Animals spreading this way and that. There were many faunal exchanges between the old world and new. And yet despite this many regions managed to house unique groups found nowhere else. One such family was the oreodonts. These cousins of sheep and pigs thrived in North America from the middle Eocene all the way to the late Miocene. They were at their peak during the Oligocene, reaching a diversity unrivaled by any other group at the time. Probably the king of them all was Merycochoerus.

Merycochoerus was a species that lived from the middle Oligocene to the early Miocene (29 to 20 million years ago). It was 900 pounds in weight, making it one of the largest animals in the mid-late Oligocene. What makes Merycochoerus unique is that it looks like a mash up of a pig and a hippo. Observe:

Skull of Merycochoerus from the Oligocene John Day formation, Oregon

Oreodonts were wildly successful during the Oligocene but lost steam after that. They stuck around until the late Miocene before finally going extinct. What happened? One thought is that as browsers oreodonts were unable to adapt to the continuing expansion of grasslands. They thrived in the woodlands of the Oligocene, but the Miocene saw the development of the savannah. Horses and other animals adapted by evolving longer legs, hooves sturdy enough to run on open ground, and high crowned teeth designed to grind tough grass. But oreodonts stuck with their shorter legs and low crowned teeth. Perhaps oreodonts, once the most successful groups of mammals in North America, went extinct out of stubbornness.

Skeleton of Merycochoerus from the Miocene of Nebraska. From flickr user Mrs Pugliano

24. Sivatherium

The giraffe is a strange if not majestic animal. It is the tallest living animal, with males approaching 16 feet tall. They have bony knobs on the top of their heads. They slurp up leaves with blue-black tongues 18 inches long. Because of their long necks and legs they have to awkwardly squat down to get a drink of water. Amazingly though, it uses those long legs to run 20 mph. Giraffes were thought to be alone on our planet until scientists finally managed to penetrate the Congo and discovered it’s cousin the okapi. Since we are so used to the giraffes of the savannah the okapi seems like the oddball. But fossils show that the modern giraffe plan is actually the odd man out.

For most of the Cenozoic the standard giraffe design was like that of the okapi: long legs but not ridiculously long; long necks but not ridiculously long; and not small modest horns but large flamboyant horns. Ceratopsian dinosaurs are famous for their variety of horns and spikes. But mammals actually created the most bizarre and strange horn shapes known. Giraffes were no exception and Sivatherium is a prime example.

Sivatherium was one of the larger members of the group, standing over 7 feet at the shoulder and weighing over a thousand pounds. Early reconstructions showed it as like a heavyset moose but more fossils and cladistic analysis now show it with the okapi like build. There are 2 species of Sivatherium and each have their one unique horn arrangements. Sivatherium giganteum from Asia had 2 small horns over the eyes and two at the back of the head that flare in an antler-like fasion (no wonder it was originally depicted like a giant deer).

Skull of Sivatherium giganteum. From Wikipedia

Sivatherium hendeyi also had two small horns above the eyes. But its back horns swept up and back, almost looking like pair of erect cow horns.

A skeletal reconstruction of Sivatherium hendeyi at the West Coast Fossil Park, South Africa. From Trip Advisor

Sivatherium maurusium, also from Africa, had two short knobs over the eyes. Its back horns are bumpy and curve forward like actual cow horns. He certainly gets an A for creativity!

Fleshed out reconstruction of Sivatherium maurusium out of those old zoo books many of us collected as a child. From girafamania.com

Like many other groups, giraffes today are but a remnant of past glory. Elephants, rhinos, pronghorns, and even humans are all extremely low in diversity compared to their fossil history. Why this is (especially in regards to humans) is a persistent enigma. Paleontology is often looked down upon as useless. But it helps answer questions like the one above. Why is this no longer a world for elephants? What allowed humans to oust their competition? And by studying why past species went extinct we can help prevent modern ones from following in their footsteps.

25. Uber bears

Bears have had many faces throughout human culture. They have been seen as cuddly critters, symbols of nature’s beauty and freedom, scourge of happy campers, ferocious killing machines, mindless man eaters, spiritual equals, cartoon fodder, and the “Ursine Al Qaeda” (as Stephen Colbert once called them). Bears are today found in the Americas and Eurasia. They run the gamut from pure carnivore to pure herbivore, though most fall in between. However some species show regional variation that complicates the picture. This little fact has made it all the more difficult to determine the lifestyles of extinct bears. The most famous is Europe’s iconic cave bear. But the America’s have given us two species that make the Cave Bear look like a pipsqueak.

The first is Arctodus simus, also known as the short-faced bear. Despite being one of the familiar heavyweights of the ice age, Arctodus isn’t as well understood as its compatriots. For example, at the La Brea Tar Pits, a very heavily researched predator trap, scientists have found over 3000 dire wolves, over 2000 sabertooth cats, but only 34 individuals of Arctodus. At Diamond Valley, which yielded tens of thousands of Pleistocene fossils, Arctodus is represented by just a single incisor. This and the paucity of remains found throughout North America should make it clear this bear isn’t giving up its secrets easily. As a result, scientists are still in disagreement over how it lived.

Arctodus was originally thought to be a hyper carnivore, using it’s long legs to run down prey. However a recent study found that Arctodus was proportioned like any other bear; stripped of flesh, any bear skeleton looks particularly leggy. But like any modern bear Arctodus was probably capable of short bursts of speed. Then a new hypothesis emerged. Rather than being a savage predator, Arctodus may have been a master scavenger. The long legs, argued the proponents, allowed Arctodus to cover large distances in search of food. Like it’s modern cousins it probably had a great sense of smell, which would come in handy when trolling the country for rotting flesh. How did a giant bear find enough flesh to eat? The idea is that there were plenty of other kids in the schoolyard to steal lunch from. Across North America there were sabertooth cats, scimitar cats, dire wolves, lions, American cheetah, and jaguar who could have been “persuaded” to abandon their kill. Remember, Arctodus is thought to have weighed 1200 pounds, and stood 10 feet tall on its hind legs. It had paws the size of baseball gloves tipped with huge sharp claws, as well as powerful jaws. It’s easy to see how Arctodus could have stolen kills from other carnivores. Hell, modern grizzlies in Yellowstone routinely steal kills from wolves. It is also suggested that those powerful jaws could be used to crack open bones to access the nutritious marrow. So how does the scavenger idea hold up?

Skeleton of Arctodus on display at the College of Eastern Utah Prehistoric Museum

Let’s start with chemical analysis. A bone recovered from Alaska underwent an isotopic study and showed elevated levels of nitrogen. This shows that its diet was almost exclusively meat. Case closed right? Not so fast. We can’t generalize based on just one find. It could be only the Arctodus in Alaska, or even just that individual, was more carnivorous. This is something that needs to be taken into consideration more. At the 2013 SVP meeting, there was supposed to be a couple posters on Arctodus from the La Brea Tar Pits (but they never got posted). One looked at microwear on the first and second molars and found that Arctodus wasn’t biting hard objects… at Rancho La Brea. Another one discussed the importance of Rancho La Brea, going so far as to say in the abstract (which is all we have): “In contrast, the material from Rancho La Brea (RLB) represents the largest sample from a single locality and provides a unique opportunity to address paleobiological questions associated with this taxon.” Yeah, but still, you’ll ultimately be understanding the Arctodus of Rancho La Brea. Reading the abstract it appears they kept this in mind. At the end they said: “Our results indicate that δ15N values varied for these bears, with some individuals in the same trophic category as sabertooth cats (Smilodon fatalis).” So it may not just be regional variation. It could be individual variation. The specimens at the tar pitsare thought to range from 40,000 to 10,000 years ago, so it could even be temporal variation.

So where does this leave Arctodus the super-scavenger? Hard to say for certain. The study above said there was no evidence of Arctodus crushing bones with its molars. But what about its other teeth? What about activities other than crushing? Numerous fossils have been found across North America showing scavenging activities by Arctodus. In each case, the size, shape, and span of the marks point to Arctodus as being the maker. The first is one of the vertebra of the Huntington Reservoir mammoth in Utah. The next is a distal femur of a mammoth from the Fairmead Landfill in California. Another is a mammoth rib from the Mammoth Site at Hot Springs, South Dakota. Finally, there is a mammoth calcaneus (ankle bone) from Saltville, Virginia, that was bitten through. While the American lion is a suspect, Arctodus is the most likely candidate. In all these instances, fossils of the bear as well as traces of its handy work were found at the site. Another odd coincidence is the fact that all the sites had mammoth and all the remains showing scavenging are mammoth. I could of course be reading too much into it.

Distal femur (the knee joint) of a mammoth that has been bitten by a large carnivore. Arctodus is implicated. At the fossil Discovery Center of Madera County

It should be obvious by now that we are nowhere near an understanding this animal. If it was as variable in its dietary habits as these studies suggest, then we have a lot of untangling to do. But it isn’t alone in this regard.
Bears were among the many “northerners” to migrate to South America. One such species was Arctotherium angustidens. The name may sound familiar because he made the news a while back. Mainly because of this image:

The mega bear Arctotherium augustidens

The scientists estimated that the owner of a gargantuan humerus may have weighed over 3,000 pounds. Remember that this is just an individual. We need a lot more fossils to be able to calculate an average. But if this is the outlier, then Arctotherium angustidens must have been one monstrous animal. But unlike Arctodus, we may have a better idea of Arctotherium’s diet. Its teeth show breakage and wear more consistent with consuming bones (whereas Arctodus appears to merely scrape and puncture them). Arctotherium angustidens is thought to have been more carnivorous than modern bears; to what degree it is hard to say. This conclusion, according to the paper, was reached by means of geometric morphometric and ecomorphology methodologies. I wonder if any isotope studies have been done?

Anyway, Arctotherium angustidens was the first, largest, and most carnivorous species of its line. There were six other species of Arctotherium that followed throughout the Pleistocene. They appear to follow a trend of reducing size and increased herbivory. The authors suggest that this may have resulted from increased competition from other carnivores, namely sabertooth cats. Again, this is just conjecture. How much hunting Arctotherium angustidens did and how much scavenging is currently unknown. We can’t just say “it was probably omnivorous like modern bears”. If the SVP poster about Arctodus at Rancho La Brea is any indication, these giant bears may have varied widely in their diets. If we are to crack this ancient puzzle, we should probably start examining (perhaps isotopic studies when possible) each individual fossil.

A gallery of short-faced bears A) Arctotherium angustidens; B) Arctotherium bonariense; C) Arctotherium vetustum; D) Arctotherium tarijense; E) Arctotherium wingei; F) Arctodus simus; G) Arctodus pristinus; H) Tremarctos ornatus (spectacled bear); I) Tremarctos floridanus. From Figueirido and Soibelzon, 2010

I’ve seen many blog posts “demythologizing” these giant bears. To me that implies that we have a solid understanding of them. It can be argued that we know more about T. rex than these bears. At least T. rex has a dozen or two partial skeletons, with a few being largely complete. So much work has been done on its size, its diet, its locomotion, its biomechanics, its cladistics and evolution. Most papers I find deal with taxonomy, biogeography, and specimen reports. I know these bears are known from mostly fragmentary and isolated remains. That just means we need to make the most of them. “More fossils” is the usual response to lack of knowledge, but we need to do something until they are found. These bears were top contenders for the largest carnivorous mammals ever known. To uncover whether or not they are as rapacious as their reputations claim, we have a lot of work to do.

26. Chin porpoise

The San Diego Museum is among the oldest in California. They don’t have that much in the way of exhibit space. But what they do have is downright phenomenal. I first visited their exhibit Fossil Mysteries not long after it opened in 2006. People fawn over the expansive halls of the big institutions like the American Museum, The Smithsonian, and Los Angeles. The collections are impressive, but I am not so easily cowed by quantity. I have been saying it for years: these big museums get away with bland and boring displays because they can rely on their huge collections and their high attendance. But I like smaller museums because they don’t have the resources (financial, scientific, etc) so by necessity they have to rely on ingenuity. This often leads to far more engaging exhibits, ones that really draw people in. Fossil Mysteries is one such exhibit. In fact, I maintain that it is one of THE best fossil displays I have ever seen.

This exhibit so beautifully tells the story of San Diego’s prehistoric past while seamlessly explaining how science works. And they really bring the fossils to life in a number of ways: half flesh/half skeleton models, a full size Eocene rainforest, models, skeletons, a fossil aquarium, and gorgeous murals by Bill Stout. Even though they aren’t from my homeland, I feel connected to these fossils. I see them much more easily as once living animals because this exhibit didn’t just throw them in a case. They took extra care to make sure these fossils were brought to life.

Since this exhibit is so damn good, I have visited it multiple times. One fossil I kept seeing was a puzzling skull in the Pliocene section:

Skull of a “chin porpoise” on display at the Sand Diego Natural History Museum

It was the third in a series of cetacean skulls discussing feeding habits. The first was a fairly robust porpoise skull with stout teeth. The exhibit reasoned it probably fed on larger fish. The next was a more lightly built skull with long slender jaws and needle-like teeth. Resembling a modern river dolphin, these jaws were used to snatch fast moving shrimp and squid. But the hird skull had no explanation of diet. That’s because nothing like it was known. It was a porpoise skull similar to the first one, but with longer jaws. The lower jaw was longer still, sticking out in front like the prow of a ship. Many times I saw that skull and the description read the same: they didn’t know how it used its funky jaw. The initial thought might have been fighting between males, jousting with their protruding chins like narwhals fight with their tusks.

Finally all was made clear a few years ago. Based on specimens from southern (San Diego formation) and northern (Purisima formation) California, scientists named the weirdo Semirostrum cerutti. Features of the jaw and skull show that there was a deeper articulation of the lower jaw and the head was more mobile and flexible; perhaps related to its super chin. They found that the closest analogue to its jaw is a group of modern birds called skimmers. They fly above the water with their lower jaw cutting through the surface to snag fish. Unless Semirostrum had a penchant for hang gliding I doubt that’s what it was using it for. There is a fish, Hemiramphus, which also has an elongated lower jaw. It feeds on microscopic plankton, so maybe the lower jaw was used to detect such minute prey. In fact, both the bird and the fish are nocturnal, so the jaw as a sensory organ makes sense. Looking closer as the jaw, the scientists found evidence of extensive nerves and blood vessels. So it appears to have been rather sensitive. I think I’ll let the authors take it from here:

Benthic probing may have evolved in low light or conditions unsuitable to extensive biosonar use for prey capture or communication (e.g., to avoid predators). The transversely thin, blade-like shape of the mandible does not seem conducive to scooping or specialized biting, as proposed in the extinct elephant-like gomphotheres, but prey may have rolled up the rostrum during a kind of skimming followed by clamping of the upper jaw after encountering prey. The streamlined mandible may have eased forward aquatic movement, with the head angled downward to monitor (via echolocation) and probe (via the mandible) for prey at the seafloor.

Today the California coast is home to many species of flatfish (halibuts, flounders, sanddabs, and soles) that are well known for hiding in the sea floor. And I’m sure there are other fish who like to hide in the sand. There is no reason to think the Pliocene was any different. Otherwise, Semirostrum probably wouldn’t have evolved such specialized gear to find them! As if that wasn’t enough, Semirostrum shares features with modern river dolphins that allow slower but more flexible swimming. The teeth are heavily worn and well rounded. This suggests the teeth were abraded and polished by a fine grained material. Like say… the kind of sand typically found on the seabed. Need I say more?

Life reconstruction of Semirostrum by by Robert Boessenecker

Semirostrum isn’t just odd for a porpoise. It’s odd for a mammal. Only the shovel tuskers had something similar, but even then the analogy is strained. This wasn’t a plow like what is thought for the elephants; this was a probe, a highly specialized organ. The Mesozoic gets all the hype for its sea monster looking marine reptiles. But it seems we are finding much stranger sea goers here in the Cenozoic. And few are more apt to lead the charge than the “chinny chin chin porpoise”

27. Top Dog and Terrible Hyena

Dogs range the world except Antarctica. From the noble wolf to the sly fox to the “baby snatching” dingo, dogs are one of the most successful groups of carnivores in the Cenozoic. So you may be surprised to learn that dogs are only recent characters on the world stage. Dogs originated in North America and remained there until just 5 million years ago. So if dogs were stuck in North America, who was doing their job elsewhere? Naturally marsupials filled the void in Australia with the wolf-like thylacines. Borhyaenids, primitive metatherian carnivores, took over in South America. As for the old world? I have another surprise for you. Filling the niche in Africa and Eurasia were hyenas.

Hyenas get a bad rap today. Often seen as ugly, nasty scavengers they have gotten the raw deal on public relations. Films like The Lion King only made matters worse, reinforcing previous perceptions that lions are strong and noble while hyenas are weak, cowardly, and even a little stupid. While modern brown and striped hyenas do scavenge, spotted hyenas are actually formidable predators. In fact, studies show that in some regions they kill more prey than lions, and in some regions lions get more food by pirating hyena kills than by killing their own prey. And the fossil record shows hyenas were never the “losers of the animal kingdom” that people often see them as.

Here we see a hyena in a typical act of scavenging /s

Throughout their evolutionary history dogs came in a range of shapes and sizes. Hyenas followed suit. One species was small and mongoose-like. Another species (Chasmaporthetes) was lightly built and probably a fast runner. There were some wolf-like species as well. So hyenas were every bit as capable as their “superior” counter parts. And since they managed to keep up with dogs it should be no surprise that when dogs produced a super-sized brute hyenas did as well.

Hyenas from the late Miocene of Europe. From left to right: Adcrocuta eximia, Hyaenotherium wongii, Ichtitherium viverrinum, Protichtitherium crassum, and Plioviverrops orbignyi. By Mauricio Anton, from the book “Mammoths, Sabertooths, and Hominids”

Dinocrocuta gigantea. The “gigantic terrible hyena” This monster prowled Asia and far eastern Europe during the Miocene. It is especially well known from China, where several complete skulls and other bones have been found.

Skull and head reconstruction of Dinocrocuta gigantea. By Mauricio Anton, from the book “Mammoths, Sabertooths, and Hominids”

Dinocrocuta wasn’t a true hyena though. It was a Percrocutid, a small group of hyena-like animals. Kind of like how nimravids are cat-like but not true cats. Anyway, Dinocrocuta lives up to its name on size alone: it’s estimated to have weighed 800 pounds. That is the size of a grizzly. And like a grizzly, it had a massive skull capable of crushing bite force. While grizzlies are usually salad munchers with a bad temper and occasionally prey on animals, Dinocrocuta was a full tilt predator. For starters are the teeth. Animals that spend a lot of time chewing plant matter have flat molars (like bears). The canines were long and point like we see in big cats. The cheek teeth, while robust and rounded (to facilitate crushing), were structured like the blade-like cutting teeth of cats. It may be contested that Dinocrocuta couldn’t have been as active a predator as other animals because it’s size meant it couldn’t run fast enough to chase down prey. One fossil reveals that they at least had the balls to go after big game. A fossil rhino skull from China was found with a bite mark near the eye:

The bone was in the process of growing back, a sign it was healing. Fossil bite marks always come with the disclaimer “it is impossible to tell whether it was attacked or scavenged”. However in this case the animal was attacked while it was alive and survived long enough for the bone to remodel. Dinocrocuta was the only animal alive at the time and place that could have made this wound. Obviously speed and agility aren’t that important when hunting things like rhinos. A rhino would have been a formidable opponent; perhaps this was a weak or sick individual; maybe Dinocrocuta caught it when it was vulnerable, like at a watering hole; or maybe Dinocrocuta was a pack hunter like modern spotted hyenas. But one thing is for certain. With their bone shattering jaws and mean streak, hyenas certainly earn their title (provided by Jack Tseng) as the “tyrants of the Cenozoic”.

To bring this entry full circle let us turn back to North America, to the dog Dinocrocuta was copying. While Dincrocuta was terrorizing the wilds of Asia, the savannahs of North America were being prowled by the largest dog that ever lived.

Skull of Epicyon from the late Miocene of California.

Skull and fleshed out reconstruction of Epicyon. By Mauricio Anton, from the book “Dogs: Their Fossil Relatives and Evolutionary History” by Xiaoming Wang and Richard H. Tedford

It was a member of an extinct subfamily of dogs called borophagines, which means “bone eaters”. This stems from the fact that a couple of their stock resembled hyenas (thus they were thought to be scavengers). But it is hard to imagine something whose name means “top dog” as being a trash picker. Epicyon haydeni was that top dog. Its skull rivals a bears in size. At 370 pounds, Epicyon was only half the size of Dinocrocuta. But as a dog, Epicyon was more suited to the open terrain. It probably preyed mainly on horses and camels, the most common animals at the time. We don’t know whether or not it was a pack hunter or a “lone wolf”. But we might be able to guess based on its leftovers:

Foot bone of a giant camel from the Miocene of California. One of the articular surfaces (the knobs at the top, where the toe bones connect) has been chewed off.

Many bones from Miocene North America show signs of having been chewed on. Anyone who has ever given their dog a bone can find the same bite marks as paleontologists do. Stuff like this and the hyena-like skulls of Epicyon and its cousin Borophagus caused paleontologists to initially class them as hyena mimics; that is, they scavenged carcasses, using their strong jaws to crush bones. But with the revelation that modern spotted hyenas hunt this interpretation was questioned. Carnivore expert Xiaoming Wang in his book about dogs posits a different scenario. He thinks the bone cracking could be a sign of group living. The idea is that rather than using strong jaws to break open the bones of carrion, the strong bite instead evolved as a means of quickly dismembering a carcass. Like hyenas, these dogs may have each torn off a chunk of the kill, bones, flesh, everything; they would then retreat to eat in seclusion. This quick dismemberment was not only a way to consume the kill before other predators caught wind. It was a way of getting your piece in the highly competitive social scene. In nature, your greatest rivals are the members of your own species.

Epicyon attempts to sink it’s fangs into the “slingshot deer” Synthetoceras (who was supposed to be the final entry on this list. Looks like he made it in anyway!). By Mark Hallet, from Fine Art America

There hasn’t been a dog since to rival Epicyon in size. Even the largest wolves are only half that weight. The true hyenas did produce a small-lion-sized species during the Pleistocene (Pachycrocuta brevirostrus), but even it pales in comparison to Dinocrocuta. Why did these carnivores get so big? What advantages/disadvantages came with such great size? Why didn’t this gargantuan size reappear during the megafaunal age of the Pleistocene (save for Pachycrocuta)? If only we could hold a biscuit over them and tell them to speak, only then might we get our answers.

28. Giant buffalo

You know, it can be frustrating at times when people don’t understand the basics of science. Like common names. Many common names are actually inaccurate. Stuff like “star fish”, “sabertooth tiger”, and “Irish elk”, to name a few. When we try to inform people it’s incorrect they often role their eyes and say “whatever” or “same thing” or (in the case of my old geology teacher) “god just let it go”. They don’t understand that such names are not only inaccurate but also misleading. They effectively rewrite the taxonomy of the animal. And because of that, we have to explain the difference to the person each and every time. The example relevant to this discussion is “buffalo” Buffalo is used to refer to many different kinds of hoofed mammals, some more closely related than others. Specifically, it refers to two species thought of as “true” buffalo: the cape or African buffalo and the water buffalo. But this name gets applied to another animal that, while related (both are in the family Bovidae), is quite different from its old world cousins.

It all started when early explorers and settlers encountered a giant hairy beast in the wilds of the American west. It was large, had horns, and walked on two toed hooves. It looked like a buffalo, so they called it one. We are of course talking about bison. The devils in the details as they say. Buffalo have short hair and large horns that usually meet in the middle to form a kind of boney helmet. Bison have shaggy coats (including a “ruff” or thick mat of hair between the horns), have smaller horns, and a huge shoulder hump. So using the title I did isn’t accurate as one of the subjects is a bison.

Bison are already big and powerful animals. Males can weigh up to a ton and stand six feet at the shoulder. They are usually ranked as the largest land animal in North America (though you could probably make the case for largest land animal in the Americas). So it’s hard to imagine a bovid bigger than it. But there was. During the ice age in North American there were two species of bison. The first was Bison antiquus which was about the same size as its modern descendant and sported a slightly longer spread of horns. The second was a giant in the tradition of Pleistocene mega mammals. It was called Bison latifrons. It looked other bison species… Except it was a foot taller, weighed half a ton more, and boasted an impressive 6-7 foot horn span!

Partial skull and horncore of Bison latifrons discovered in Diamond Valley, California

Reconstructed skeleton of Bison latifrons at the Royal Saskatchewan Museum. From travelphotobase.com

Those horns are its claim to fame. Although the horns on modern bison are nothing to laugh at. Case in point:

Ouch…

Pwned!

Now image the same thing happening with a bigger animal with much bigger horns. People always fear the carnivores. In doing so they forget that the herbivores can be even worse. For all we know there may have been some paleo-indian hunters who met a similar fate. But the horns may have been even longer. The fossil record preserved the boney inner cores. In life horns are covered by an outer layer of keratin. These usually add some more length to the horns.

Now to move on to buffalo proper. Again, it appears to be a case of one ecosystem trying to have its own version of an animal elsewhere. This lead us to the African giant buffalo. Now this guy was only slightly larger than its modern cousin. But it was a good deal more robust. And like Bison latifrons, it is famous for its horns. Skulls of Pelorovis antiquus have been found with horns stretching 9 feet long! I’m pretty sure just one of those bad boys puts any dinosaur horn to shame. But appearances can be deceiving. The horns of Pelorovis antiquus curve much more heavily than the straight horns of Bison latifrons:

Skull of Pelorovis antiquus from eastern Africa. From Wikipedia

Fleshed out reconstruction of Pelorovis antiquus (bottom). By Mauricio Anton, from the book “Evolving Eden”

This means that while their overall length could be nine feet, the distance from point to point is shorter. And like Bison latifrons, the horns would have been longer in life because of the keratin sheath. Horns are not just good for fighting rivals and attracting mates. They can also be used for protection. While it is debated whether horned dinosaurs used their head ornaments for defense against predators, mammals could use their to thrash would be predators. Case in point:

Weeee, flying kitty! Apparently the lions were mating when the buffalo randomly attacked them. What a 2000 pound cockblocker!

The phrase “that’s gonna leave a mark!” feels like a gross understatement here… (she did survive, thanks in no small part to wildlife vets)

Yeah, mammals ain’t no wusses! They get down and dirty and ain’t afraid of a good brawl! Pelorovis antiquus probably needed all the help it could get living in Pliocene Africa. In addition to all the modern predators (lions, hyenas, hunting dogs, leopards, and cheetahs), the sabertooths were also in force. These included the lion-size Homotherium, the leopard-on-steroids Meganterion, and the beefcake Dinofelis. As the above shows modern buffalo are already very dangerous. One can only imagine how nasty a giant buffalo could have been. The same likely goes for Bison latifrons. Like a lot of mammals they were as dangerous as they are majestic. They lucked out in having horns they could use for defense. Others had to make due with less.

29. Bull rat

Rodents get no respect. They are seen as vermin, as disgusting pest who need to be eradicated. Rodents are abundant microfossils, yet hardly anyone wants to study them. All this despite the fact that rodents are actually the most successful group of mammals. Half of all mammal species living today are rodents. They live everywhere except Antarctica. They are found in just about every habitat imaginable. They are highly adaptable, thanks to their varied diet and high rate of reproduction. They serve many important roles in nature and science. Rodents are an important source of food for hundreds of species. They serve as seed dispersers. We use them for laboratory experiments. Ice age pack rats nests in the American southwest have survived to present and help reconstruct the ancient climate. One modern rodent species even predicts the weather for us. Because rodents have much shorter generational cycles, they evolve quicker than large mammals. This allows them to be used as index fossils, a method of dating prehistoric sites and geologic units. And they sometimes amuse us with their hilarious antics:

A good sized rat seems capable of scaring a good amount of people. But there are many species larger than the biggest rats. Maras, porcupines, and beavers all fit the bill. The largest living rodent is the capybara. Like a giant amphibious guinea pig, it can weigh over 100 pounds. It is native to much of central and eastern South America. You would think that this was as big as a rodent could get. After all I mentioned rodents as microfossils. As is usual with the fossil record, what we perceive as an extreme is easily outclassed. The capybara is the last in a long parade of giant rodents who occupied South America during the late Cenozoic. Funnily enough, they got bigger with each new discovery. The first was Neochoerus, a larger cousin of the capybara. Then came Telicomys. I’ve heard the name translates as “mighty mouse”, which is apt. It was 6 feet long and weighed in the neighborhood of 800 pounds. Telicomys enjoyed the spotlight as the largest rodent for a long time. Then in the 80s along came Phoberomys. This mega rodent from Venezuela pushed the envelope on rodent size to 1500 pounds. You would think that would be the end of it. It wasn’t.

Phoberomys from the Miocene of Venezuela. Here we see the creature briefly enjoying the title of largest rodent ever. From National Geographic News

In 2008, scientists reported on a giant skull found in the Pliocene of Uruguay. It measures 21 inches long- the size of a bull’s. A giant pair of curved incisors, a foot long, marks it as a rodent. Based on the dimensions of the skull, the scientists estimated that this gargantuan rodent stood 6 feet at the shoulder and tipped the scales at a full ton in weight. This beast, the largest rodent ever found was named… Josephoartigasia monesi. Huh. Could they have picked a more convoluted and mind-numbingly difficult to pronounce name? I still have no idea how to say it’s name. So I have come to call it the “bull rat”. Why that name? Well it is as big as a bull, and it’s a rodent and rats are the most familiar (even though they are in a completely different family).*.

Skull of the bull rat (reconstructed bits in grey) compared to a distant modern cousin.

Bull rat compared to the largest living rodent (the capybara) and a human. From Prehistoric Wildlife.com

So just how did the bull rat live? All we have is a skull but can provide some details. It was found in deposits consistent with a swampy, marshy type of environment with forests. It probably fed on soft vegetation, based on its small teeth and weak chewing muscles. The bull rat shared it’s environment with many predators, including sabertooth cats and terror birds. Its size alone probably served to deter some predators. For others, like any other rodent, it probably turned to its huge incisors. Rodents make their living by gnawing. Their teeth are constantly growing to keep up with constant biting. In fact, if they don’t gnaw, their teeth can grow too long with nasty consequences:

Skull of a squirrel who didn’t keep his teeth nice and trim. It ended up curling into his skull and stabbing his brain. On display at Ye Olde Curiosity Shop in Seattle, Washington

I once saw a video of anaconda preying on a capybara. Even though the snake won, the capybara managed to take a huge bite out of it. Anyone who has ever owned a rat or a hamster knows how hard they can bite. Anyone who foolishly fed the squirrels at the Grand Canyon knows the wrath of rodent teeth. Imagine being bit by a beaver, which famously uses its teeth to cut down small trees. It’s chewing may have been weak, but it may still have had a strong bite. A biomechaqnical analysis is needed.

Skulls are good, but even they can only tell us so much about an extinct species. The size estimate, while spectacular, is only guess work. Phoberomys’s size was more reliable because post cranial bones are known. Without them, we can’t know how big the bull rat truly was, how it moved, and how its body functioned. But what the size estimate helps to establish is that rodents have the second greatest size range of any group of mammals (surpassed only by the diprotodontine marsupials of Australia). And it also reveals a rodent that would have been any exterminator’s worst nightmare.

*(Yes, i’m using my own nickname for this animal. Look, this is the single most diffiuclt prehistoric name i have ever encountered (even more so than the dinosaur opisthocoelicaudia. Does that mean mammals have another record over dinosaurs: most difficult scientific name to pronounce?). It needs a common name everyone can say. Besides, if Brian Switek can attempt to make the nickname “shovel-beaked” a thing, then i reserve the right to try and make bull rat a common name!)

30. Marsupial lion

In the past marsupials had to work to gain the begrudging respect of paleontologists. Always thought to be inferior to placentals, the storied past of Australia’s fossil record has slowly overturned these prejudices. I say slowly because as I have laid out earlier Australia has a poor fossil record compared to the rest of the world. Despite a few exceptionally rich sites (Riversleigh, Alcoota, and Naracoorte Caves, as well as a few others), our picture of ancient Australia remains frustratingly incomplete. The Pleistocene remains the best known time period, but even then it took a long time for ancient marsupials to get their dues.

In the 19^th century a shipment of fossils was sent from Australia to the eminent naturalist Sir Richard Owen. Among them was a partial skull with unusual cheek teeth. They looked like the blade of a cleaver. This lead Owen to describe the animals as “the fellest and most destructive of predatory beasts.” He named this nasty piece of work Thylacoleo, the “marsupial lion”. This was something truly apart from the known mammalian predators at the time. Unfortunately that fact alone caused future scientists to doubt Owen’s assessment. As more fossils were found, it’s lack of cat and dog like canines and cheek teeth resembling carnassials were cited as evidence that Thylacoleo couldn’t have been a predator. Combine this with the fact that it is part of the larger group that includes wombats and the diprotodonts (both herbivores) and it seemed the case was closed. Thylacoleo was a harmless herbivore. This in turn fueled the idea that the Pleistocene Australian carnivore guild was “ruled” by reptiles. Fortunately this was not to be.

Skeleton of Thylacoleo carnifex at the Melbourne Museum

Future work done by Stephen Wroe and others reaffirmed Owens original interpretation. Firstly, just because an animal has different dentition than a known predator does not automatically mean it wasn’t a predator itself (T. rex knows what I’m talking about). Thylacoleo has a pair of huge lower incisors that could have been used as bayonets. Of course, it takes a lot of bite force to cause lethal damage with a tooth. That’s where Wroe comes in. He specializes in studying the biting mechanics of modern and extinct carnivores. He examined the skull of Thylacoleo and used measurements to determine its bite force. Another bit of evidence used to peg Thylacoleo as a vegan was its size. At the size of a leopard, it was much smaller than most mammalian super predators. Studies lead by Wroe reevaluated Thylacoleo’s size as between 200 and 280 pounds, the size of a jaguar and some of the smaller subspecies of tigers. But back to the bite. Wroe and his team discovered that not only was Thlacoleo a big biter, but maybe one of the biggest biters of them all. It was found to have the same bite force as a lion: 600 psi. Thylacoleo was only half the size of a lion and yet it had just as powerful a bite. This means Thylacoleo had a much more powerful bite relative to its size.

Thylacoleo’s dentition was also looked over again. Herbivores spend a lot of time chewing, so they have flat teeth designed to grind plant matter. Thylacoleo’s cheek teeth are the complete opposite, looking more like bolt cutters than typical plant eater teeth. Compare them to the teeth of the supposedly superior placental mammal:

Comparison of the dentition of Thylacoleo carnifex and an African lion

Now which one looks more suited to slicing? My money is on the marsupial lion. Thylacoleo is now considered the most specialized mammalian carnivore of all time. Looking at the evolution of marsupial lions, we can see a trend towards increasing specialization of cutting. Observe:

Increasing specialization of the cheek teeth in marsupial lions. from bottom to top: the Miocene Wakaleo alcootaensis; the Pliocene Thylacoleo crassidentatus; and the Pleistocene Thylacleo carnifex. From “Prehistoric Mammals of Australia and New Guinea” by Long et al

So Thylacoleo wasn’t only on par with placental carnivores, it surpassed them. Thylacoleo’s build offers further clues to its predatory nature. This was a very heavily built animal. It’s very robust limbs show it was built for power like sabertooth cat. It had large claws on semi-opposable thumbs, a trait not seen in any other predatory mammal. These may have allowed Thylacoleo to better grapple with it’s prey. Now with its predatory creds restored, we need to ask next what it hunted. It certainly had its pick of megafauna to snack on. A couple species of the huge wombat-like diprotodonts (Diprotodon and Zygomaturus), a large flightless bird (Genyornis), the marsupial tapir, a giant wombat (Phascolonus), and a suite of large to giant kangaroos (Procoptodon, Sthenurus, Macropus titan, and Protemnodon, a giant wallaby). Strange cut marks attributed to Thylacoleo have been found on some ribs belonging to Diprototodon, a three ton behemoth who was the largest marsupial of all time. Whether Thylacoleo killed it or scavenged it is hard to pin down. Despite being a very powerful predator, it is debatable whether or not Thylacoleo could take down such a huge animal. Whatever it went after, we can safely say that Thylacoleo was an ambush predator. It was designed to overpower its prey, not run them down.

A pair of Thylacoleo in the process of taking down the robust sthenurine kangaroo Sthenurus. By Mauricio Anton, from “National Geographic: Prehistoric Mammals”

Thylacoleo shared its spot at the top of the food chain with the giant lizard Megalania. But being a mammal, Thylacoleo had a hire metabolism and thus would have needed to hunt more than its reptilian cohort. This of course means it probably had more of an impact on the ecosystem. And like Megalania, Thylacoleo is thought to have died out ~50,000, probably following its giant prey into extinction. Or did it. A piece of rock art discovered in Kimberley in 2008 may depict a marsupial lion:

Possible depiction of Thylacoleo in aboriginal cave art. From Antiquity

The rock art may date to 30,000 years ago. That’s 20,000 after Thylacoleo is thought to have gone extinct. The short legs, large head, wide paws make some think it represents Thylacoleo. A second image may also depict Thylacoleo:

Possible depiction of Thylacoleo in aboriginal rock art. Here we see a man trying to fend off the creature with a spear. From Antiquity

Could this be the world’s oldest action movie? Of course determining that these pictures depict marsupial lions is very difficult. Especially when you consider that the youngest dates for Thylacoleo are so old (and evidence for humans at this time is very, very rare, practically nonexistent). The common counter argument is that the images depict thylacines, marsupial wolves. These critters survived on the Australian mainland until the introduction of dingoes around 3,000 years ago. After that it was restricted to the island of Tasmania until being driven to extinction by white settlers (the last one died in captivity in 1936). After all, thylacines are known to have striped backs. Being known from fossil bones, we can only guess as to what the marsupial lion actually looked like.

Thylacoleo has had a rocky history but he came out on top. He showed that marsupials could produce large predators on par with placentals. Well not only that but he turned out to be the most specialized carnivorous mammal that ever lived. It was a powerful and likely vicious animal, if it had an attitude anything like that of its distant cousin the Tasmanian devil. There is evidence it may have taken down the largest known marsupial. There is evidence it may have survived longer than previously thought and may have even done battle with humans. Why we don’t see tv shows and movies showing prehistoric Aborigines going toe-to-toe with a marsupial lion (or Megalania) like we see cavemen fighting sabertooth cats is beyond me. Why this true badass of prehistory isn’t as celebrated as other prehistoric carnivores (mammal or otherwise) is maybe one of the great crimes of modern paleo culture.

31. Crusher and Killer Walruses

A long long time ago we looked at a dolphin who thought he was a walrus. Now it’s time to look at walruses proper. The group of sea going mammals we call walruses date back to the middle Miocene and contained three subfamilies: the sea lion-like Imagotariines, the double-tusked Dusignathines, and the tusked Odobeninines (which includes the modern walrus). The two we are looking at belong to the second group. Dusignathines swam the waters of the Pacific during the late Miocene and most of the Pliocene. They get their nickname of “double-tusked” because they sport two sets of bear-like canines as opposed to the two large upper tusks of their modern cousins. This combined with their full set of teeth show their feeding habits differed significanty from those of modern walruses.

First up is a denizen of sunny Orange County, California. Named in 1991, it is called Gomphotaria pugnax; the “pugnacious wedge seal”). Hailing from the late Miocene Capistrano formation, this is one of the pretty cool animals that you never heard of not just because it sits in a museum collection no online database, but also because of the specialized nature of marine mammals. I know of it because I found it referenced in the L.A. Museum’s collections newsletter and managed to get a couple of the paper. But it’s best public exposure comes from Boesnecker’s thorough, exhaustive blog. In fact that is where a lot of my info on this guy comes from, so be sure to thank The Coastal Paleontologist. Anyway, Gomphotaria is known from a nearly complete skeleton, including a whole skull and the right lower jaw. The first thing that leaps out about Gomphotaria is its size:

Lower jaw of Gomphotaria pugnax with puny human for scale. Photo by Robert Boessenecker

I haven’t heard any size estimates for this guy, but just looking at Boesnecker’s photos, this guy may have been the size of a Steller sea lion or maybe even a mid size elephant seal. The skull is massive:

Gargantuan skull of Gomphotaria pugnax. Photo by Robert Boessenecker

Even for the double-tusked walruses, the canines of Gomphotaria stand out. They are huge and thick, looking like they were designed for crushing. So do its cheek teeth. They are short and rounded, not ideal for catching fish. Wear on the teeth seem to suggest this. Gomphotaria outright crushed its shellfish prey instead of sucking them out like a modern walrus.

So we have one walrus who didn’t pussy foot around with sucking clams. He just smashed them like a boss. But this isn’t the only extreme deviation from traditional walrus diet. What is I told you there was a killer walrus? Sounds crazy right? Not to the scientists who described Pelagiarctos. Pelagiarctos was found in the legendary Sharktooth Hill bonebed outside of Bakersfield, California. Only a few teeth and the front of a lower jaw were found:

Based on the shape of the teeth, the broken lower canine, and the fused nature of the lower jaw was at first interpreted as evidence of a carnivorous diet. Estimated to weigh 1000 pounds (the size of a modern leopard seal) it was certainly big enough to prey on a variety of marine vertebrates. And so the image stayed until just a couple years ago when another specimen belived to be Pleagiarctos showed up in Orange County.

The lower jaw wasn’t fused, and the teeth were in great shape. The authors argue that this means it was probably a fish eater and not a macro predator. I say there are too few fossils to say with any certainty. Even if it was a fish eater, it could still have preyed on other things. Its teeth are somewhat similar to a leopard seals. Leopard seals fed mainly on squid and krill, but have been known to prey on penguins, other seals, and have even been observed to have taken bites out of whales! Like I said, I think too few fossils have been found to say anything for sure (a skull would be nice for starters). So with Pelagiarctos debunked as a macro predator there seems no hope for a killer walrus. Or is there?

I have seen Boessenecker mention a few times something called Pontolis magnus. I haven’t been able to track down any literature on the damn thing, so he has been my source of info. Apparently it’s known from a cranium (the back of the skull) from Oregon as well as a lower jaw. Nothing much can be said about him. Boesnecker says it certainly ate fish but was in the size range to be a macro predator. I hope so. I just love the name Pontolis magnus. It sounds like the name of some brutal and ruthless Roman general or emperor.

Does all seem lost for the killer walrus? Maybe not. Like I said, we don’t know very much about the claimants. They may very well have been like modern leopard seals, which do occasionally prey on birds and mammals. But being a killer may run in the family. Boesnecker notes that modern walrus have been observed preying on sea birds and even seals, using their specialized feeding equipment to suck the meat and blubber off the bones. When I was a kid I read of a bizarre fight witnessed by the crew of a Russian ship in the Arctic. According to the account, a walrus was locked in a death match with a narwhal. It said the walrus won and proceeded to feed on its slain foe. So remember: behind the silly sounds and cuddly look, lurks the heart of a blood thirsty killer!

Like so many groups, scientists are left wondering why such a diverse group has left so few descendants. The modern walrus is the only species left. And they may soon be gone as well. As the climate changes, the arctic sea ice that walruses rely on is shrinking. Walruses may soon join the ranks of animals known only from fossils and museum specimens. Let’s hope not.

32. Doedicurus

Ankylosaurus are often described as living tanks. They are heavily armored and have tails ending in nasty clubs. They are often portrayed as being almost immune to attack from predators. Anything that attacks them can’t get through their and face the wrath of their tail clubs. But they aren’t the only ones. Mammals produced their own tanks-like animals. Not only were they more fortified than ankylosaurs, but one species was even able to one up them on tail clubs! These animals are the glyptodonts.

Glyptodonts are extinct relatives of armadillos. They first appeared in the early Miocene and seem to have reached their peak in the Pliocene and Pleistocene. They ranged in size from a giant tortoise to a Volkswagon bug. Like other members of Xenarthra (sloths, armadillos, and anteaters) they had no tooth enamel, so their teeth were constantly growing. Unlike ankylosaurs who had armor plates embedded in their skin, glyptodonts had a rigid shell. This shell was domed and was made up of “rosette” shaped scutes that were fused together. These scutes are different between species, so they have some taxonomic value. While the shell is similar to a tortoise’s, glyptodonts couldn’t withdraw their heads. So glyptodonts had a cap of armor scutes on their heads.

Skeleton of the glyptodont Doedicurus. From Wikipedia

Their tails were also sheathed in armor. While ankylosaurs had a fairly standard blueprint for their clubs, glyptodonts were much more diverse:

Lateral (above) and dorsal (below) views of caudal bony sheaths: Neosclerocalyptus spp. (a), Pseudoplohophorus
absolutus (b), Panochthus tuberculatus (c), Castellanosia spp. (d), Doedicurus clavicaudatus (e). The solid circles indicate the
positions of the centre of mass (xcm) and CP using 1400 kg m23 for internal density. The error range for xcm and CP based
on variations of internal density are shown. Scale bar, 15 cm. From Blanco et al, 2009

One species stands out, however. Not only did it have a tail club, but it was a club more extreme than any ankylosaurs. Its name is Doedicurus. Doedicurus was one of the largest glyptodonts, standing 5 feet tall at the top of its dome and weighed two tons. It lived throughout the Pleistocene epoch and ranged over much of South America. But its most notable feature is its tail club. Whereas ankylosaurs are content with knobs, Doedicurus took it to the next level. This thing had a frickin morning star on the end of its tail:

The glyptodonts Doedicurus (foreground) and Glyptodon (background) hanging out in Pleistocene South America. From Wikipedia

The clubs that have been found have pits that scientists think betray the prescience of spikes. It has been posited that the club, like other glyptodonts, could have been used for defense against predators (as if the armor wasn’t enough). But the club may have also been used in fights between males. Dents and fractures have been found on some glyptodont shells which authors argue could have been made by another glyptodont’s tail club. Besides, the big domed shell of your fellow glyptodont is an easier target than a smaller and more nimble predator. But how strong was it? A study by R. Ernesto Blanco et al. found that the tails and clubs of many glyptodont species were designed to exert maximum force when swung from side to side. They found the “sweet spot” of percussion wasn’t the very tip of the club, but closer to the base. This is where the largest pits (which would have supported the largest spikes) are found. Anyone would hate to be on the wrong end of that:

A terror bird reconsidering being Doedicurus’s predator. From BBC’s “Walking with Prehistoric Beasts”

How much force these biological battle maces exerted the authors did not say. But they found that tails with smaller clubs were more flexible than those with large ones. This means Doedicurus had the least maneuverable tail of the species studies. But the tail must have been capable of energetic blows, since the animal would have had to have been accurate enough to strike with the “sweet spot”. What significance all this has requires more study. Not all glyptodonts had tail clubs and the ones who did exhibit a diversity of shapes.

Glyptodonts were the giant ground sloth’s partner in crime in the early days of paleontology. Common museum displays had glyptodonts alongside giant ground sloths. They were almost as big, and were even stranger. Of course they too got kicked aside in the public eye once dinosaurs showed up; especially the nodosaurs and ankylosaurs who were not only bigger but also had strange assortments of spikes. But unlike dinosaurs, Pleistocene humans would have seen glyptodonts in person. How I envy them. South America (in addition to Australia and Madagascar) is one of the places I wish the megafauna hadn’t died out. It had so many strange and wonderful beasts roaming its wilds. It had the remains of Souther America’s old order (ground sloths, glyptodonts, litopterns, toxodonts, and terror birds) but also put twists on the immigrants from the north. The mastodonts (Stegomastodon and Cuvieronius) were members of the old gomphothere family that had died out elsewhere but thrived in South America; the horse Hippidon had a large nose and upper lip; their species of Smilodon was the biggest sabertooth cat ever. Like Australia and Madagascar, this was a fauna unlike anything else on earth. Most wish they could go back to he Mesozoic and see the “terrible lizards”. I wish I could go back to the Pleistocene, yesterday in geologic time, and see some of the most spectalucar animals who ever lived. Doedicurus among them…

Lucky stone age bastards… From ANIMALES EN VIA DE EXTINCION

33. Basilosaurus

We saw the ultimate killer whale in Levyatin. Now let’s meet the original killer whale. Whales were originally thought to have evolved from hoofed carnivores called Mesonychids (like Andrewsarchus from earlier). Numerous fossil discoveries have revealed they actually evolved from the group of even-toed hoofed mammals called artiodactyls. In addition to this, numerous fossils have helped flesh out the evolution of whales. From the early partly aquatic Pakicetus, to the fabled “missing-link” Ambulocetus, to the freely swimming Rhodocetus. But before these guys made waves in the science community, another whale provided the first clues to their terrestrial roots.

In the early 19^th century large vertebra were routinely found in the American South. A couple specimens were brought to Sir Richard Owen (him again!) and he named them Basilosaurus. Basilosaurus means “king lizard”, an allusion to how he thought they came from a giant reptile. Later much more complete skeletons were found, including skulls. They showed that rather than a reptile, Basilosaurus was actually an early whale. But due to the rules of taxonomic nomenclature, the name had to stick.

Toothy skull of Basilosaurus. From Wikipedia

Basilosaurus skeleton in the old “Life in the Ancient Seas” exhibit at the Smithsonian’s National Museum of Natural History. From the Smithsonian website

Basilosaurus, like so many whales, was very large. It measured 50 feet long and weighed 20 tons, making it the largest animal on earth at the time. It swam in the warm waters of the late Eocene epoch around 40 million years ago. Because it lived in warm waters it lacked the thick layer of blubber worn by its modern relatives. This gave Basilosaurus a serpentine appearance, adding more to its image as a sea monster. Basilosaurus was an archaeocete, the group of early whales who made the journey into the sea. In fact, Basilosaurus provided some of the earliest evidence of this transition. When the more complete skeletons were being found, some were found with a pair of diminutive hind limbs. They were remarkably formed, from the pelvis down to the little bones of the toes. The legs were small, no bigger than a man’s arm, clearly unable to support its weight out of water. These legs were remnants of its past on land.

The diminutive hind legs of Basilosaurus. Photo by Richard Barnes, from “Why Evolution is True”

Basilosaurus had much different teeth than modern whales. Modern toothed whales have uniform teeth. Basilosaurs, again keeping with its land dqelling ancestors, had many different teeth. At the front were incisors and canines and in the back were shearing cheek teeth. The front teeth would grab hold of prey and then the back teeth would slice through flesh so it could be swallowed. Being the largest predator on earth, there was nothing Basilosaurus didn’t consider lunch. Luckily we have gut contents (in the shape of balls of indigestible bits, called bolas):

Fossil bolas- or in laymen’s terms, a petrified ball of gut contents

Teeth and bones of fish and sharks gleaned from the bolas

These fossilized gut contents reveal what Basilosaurus ate. They contain mostly fish bones and shark teeth. However, Basilosaurus was probably able to snack on its smaller cousins like Dorudon (or at least their young). Earlier whales were only able to tackle fish, but having everything in the sea potentially be on the menu meant Basilosaurus was the original killer whale.

The archaeocetes eventually went extinct. They were an evolutionary dead end. Other whales were to give rise to the lineages that would lead to the animals we charge tourists to watch from boats today.

34. Pelagornis

What do people most fear when they go to the beach? Well yeah sharks, but that’s only if they go into the water. Give up? Seagulls! That’s right, a shark may bite you if you go in the water, but a seagull can strike anywhere! They drive people mad with their irritating cawing. Their devious methods rob the unaware of their precious food. And many unfortunate souls are claimed by their bombing raids (you know what I’m talking about!). Seagulls are the scourge of the sea, coast, and even lakes. But I’m here to tell you it could be worse. Much worse.

Yes not only do they steal our food and poop on us they also… proselytize!!! From funny-pictures.picphotos.net

Sea birds are very well known from marine deposits as far back as the cretaceous. After the K-P extinction, they diversified into all new forms and niches. One group emerged shortly after the mass estinction and forged a lineage that lasted until the end of the Pliocene. If seagulls vex people today, imagine their reactions if they saw one of these flying over head. These birds are the Pelagornithids.

These sea birds are like seagulls on steroids. They varied in size. The largest is Pelagornis sandersi. Known from the early Miocene of South Carolina, this animal is known from a skull as well as some bones of the wing and leg. Based on measurements of the wing bones, it is estimated to have had a wingspan of 20 to 24 feet. The news hailed this as the largest flying bird ever. Argentavis from the Miocene of South America has been estimated to have a wingspan of 27 feet. This estimate has been challenged, often citing the incompleteness of Argentavis (not like Pelagornis sandersi is any better). So the largest flying bird title is currently up in the air. But it is obvious that Pelagornis sandersi dwarfs the wandering albatross, whose 13 foot wingspan is the greatest among modern birds.

Comparison of Pelagornis to the two largest flying birds. From Sci News.com

So Pelagronis was plenty big but it had another feature that would give any beachgoer a healthy fright. Pelagornithids are also known as “false-toothed birds”. They get this name from the fearsome points lining their jaws. These look like teeth. But these are actually bony projections of the jawbone. These probably served the same function as the pointy teeth of other marine critters; that is, they were used to grab slippery prey. These birds were once thought to be dive bombers, like gannets and brown pelicans. But given the thin walled (and therefore highly fragile) nature of their bones, this is highly unlikely. They probably snatched prey while flying just above the surface or swimming on the surface.

Skull of Pelagornis sandersi showing off those fearsome looking bony “teeth”. From Sci News.com

These birds died out at the end of the Pliocene. I haven’t heard of any reasons for why that is. It couldn’t have been competition from mammals as they coexisted for millions of years. Bird remains are always rare in the fossil record. But perhaps we can tease enough fossils out of the earth to determine why they died out. But these giant birds in flight must have been one of the most spectacular sights in the history of the earth.

35. Sloth Lemur

Writing this post I realized that I had left something out, something from one of my favorite times and places. So this last slot got axed and handed over to one of the most bizarre primates who ever lived.

Megafauna is a word used to describe a collection of gargantuan beasts. But I have found that it can be relative. What is considered giant for one area can be puny by the standards of another. It once irked me so when I saw the Dune Center calling deer and black bears megafauna. But one ecosystem helped me understand that megafauna is merely in relation to what we see today. It had a couple giants, but the rest are pretty small by comparison. But they were behemoths when placed side by side with their modern relatives. I am talking about an island off the coast of Africa that is legendary for its strange wildlife: Madagascar.

The interesting thing about Madagascar’s megafauna is not just its size and composition, but also its age. Megafauna are usually associated with the ice age (the late Pleistocene one specifically). Madagascar’s megafauna went extinct a mere 2,000 years ago. The time when the Roman Empire was at its peak; when the pre-classic Maya were building cities in the jungle; and when a certain Jewish carpenter was supposedly born. In fact most of the remains from Madagascar’s megafauna have been found as subfossils. These are bones and other remains that are on the way to becoming fossils. But they haven’t had enough time to be completely turned to stone. These remains have been found in many open air sites but a great deal have been found in caves.

A recent (and surprising) discovery was a treasure trove of subfossils in an underwater cavern. Image from the Daily Mail

A recent (and surprising) discovery was a treasure trove of subfossils in an underwater cavern. Image from the Daily Mail

Madagascar had a collection of megafauna like nowhere else on earth. There were several species of elephant birds, the largest of which weighed 1,000 pounds and laid eggs 200 times the size of a chicken egg. There were several species of pygmy hippos the size of cows. Giant tortoises with three foot shells joined the ranks of the megaherbivores. A species of strange aardvark-like animal called the bibimaligasia trolled the forest floor for ant and termite nests. The large carnivore guild was also quite unique: two species of fossa (the modern one and a larger extinct species), two species of crocodiles (the modern nile croc and the extinct Voay), and an extinct species of crowned eagle. But the biggest component, as it is today, were lemurs. In addition to the modern species, the extinct lemurs greatly swelled their diversity. There were many lemurs who actually lived on the ground. There were two species of Archaeolemur (the larger of which was around 50 pounds in size) and a larger short skulled animal called Hadropithecus. The largest lemur of all time lived on the ground. It was called Archaeoindris and is estimated to have weighed in upwards of 400 pounds, the size of a male African gorilla (the largest modern primate). Because it was so big scientists reason it lived on the ground. Up in the trees lemurs were equally numerous. Pachylemur resembled modern ruffed lemurs but was twice as big. Megaladapis was as big as a man. There was a larger species of the curious aye-aye. Finally there was a group of lemurs who took to an extreme life style. They are known as the sloth lemurs.

There were many species of sloth lemur. There was Babokotia and then 3 species of Paleopropithecus. These animals got their names because when their remains were first found they were thought to have come from sloths. This is yet another remarkable example of evolutionary phenomena given to us by the Cenozoic (in this case, convergent evolution). The long nature of the hand and finger bones, plus the curved hand bones, strongly parallel new world tree sloths. These lemurs elected to copy sloths and resigned themselves to a life upside down. The two larger species of Paleopropithecus are estimated to have weighed 80 pounds.

Palaeoprothecus climbing the trees of ancient Madagascar. From Wikipedia

“This skelenton of a Palaeopropithecus, an extinct sloth lemur, is housed at Duke’s Division of Fossil Primates. Photo courtesy of Division of Fossil Primates.”

Sloth lemurs probably spent their days lazily climbing through the forest canopy munching on leaves. Whether it was as slow as a sloth is uncertain. Sloth are very slow because they have extremely slow metabolisms. I’m curious as to whether the upside-down lifestyle allows or even necessitates the extremely slow metabolism. Maybe Paleopropithecus had a more normal (for a lemur anyway) metabolism and so would have resembled a more active sloth.

Living in the trees likely afforded protection from predators. But not all of them. Several bones of Paleopropithecus, particularly the shoulder blades, exhibit large puncture marks. These resemble the marks on monkey bones that were killed by African crowned eagles. These eagles have been observed to prey on animals as large as juvenile antelope, but regularly prey on monkeys. These could range up to 20 pounds. Paleopropithecus is obviously much larger than that. But clearly subadults who weren’t fully grown could have been prime targets. It has been posited that the extinct Malagasy crowned eagle could have simple killed the large lemur and then let it fall to the forest floor where it could then feed on it.

“Stephanoaetus mahery- a Presumed Primate Specialist and it’s Role in the Evolution of Behavioral Aspects of Living and Extinct Lemurs” by Velizar Simeonovski. A subadult sloth lemur (Paleopropithecus ingens) about to meet its doom at the hands of an extinct Madagascar crowned eagle.

The vicious talon marks of eagles aren’t the only thing scientists have found on the bones of Paleopropithecus. Some bones from this animal were found with cut marks on them. The kind made with an iron knife. This implies that Paleopropithecus was hunted by humans. Madagascar is another ring where the causes of megafauna extinction are slugged out by scientists. Was it over hunting or was it climate change. Indeed evidence shows that about 2,000 years ago Madagascar’s climate greatly dried out. This would have stressed not only the water loving species (hippos, crocs, and certain birds) but would have reduced the forests where many lemurs lived. As the forests became more open, they had to come down to the ground to move between trees (leaving them vulnerable to predators, including humans). Just like everywhere else, so much work has yet to be done.

Like the Pleistocene of Australia and South America, I find the loss of Madagascar’s megafauna is a bitter pill to swallow. Sure the modern inhabitants are wonderful and wondrous. But imagine if the past inhabitants survived until today. Imagine zoos stocked with giant wombats, Megalania, marsupial lions, and enormous kangaroos from Australia; giant sloths, armored glyptodonts, mastodons, and sabertooth cats from South America; and cloth lemurs, pygmy hippos, and elephant birds from Madagascar. These lost worlds could have been ecotourist rivals to Africa. How would the prescence of these animals have affected the indigenous cultures? How would they hunt them: How would they factor into their stories and legends? One can only speculate. And perhaps the reason they are so fascinating is because they are gone. We can go to a zoo and see animals. People who lived on the edge of the wild see plenty of wildlife. But the extinct megafauna… they offer a shocking contrast to our modern world. We can only guess and imagine how they lived and died. There is talk about how we just might be able to bring some extinct species back to life through genetics. No dinosaurs mind you, but things like the woolly mammoth, the Tasmanian wolf, and even the dodo. Many balk at the idea, while another great number think we shouldn’t do it (moral issues, because their ecology no longer exists, etc). I would be a horrible regulator, because I’d let scientists resurrect extinct species just for the chance to see them alive. But I’m not holding my breath. Science is science, after all, and the kinds of resurrection we see in movies may never be within our grasp.

So for now we must take what we can get. I am glad that most of the extinct beasts of Madagascar left us many subfossils to marvel at (except for Archaeoindris, who is curiously only known from a complete skull and a couple post cranial bones). They let us imagine in more detail about a lost world so similar to the modern ecosystem but so different at the same time. When lemurs reigned supreme, and one species dared to go the road less traveled and copied perhaps the last animal anyone would think to. Perhaps the habits and convergance of the sloth lemurs is a mystery that may remain, whether as a subfossil or a live specimen born in a test tube.

And with that ends the longest post I have ever written. I have spent over 2 months on it, so i hope you enyoyed it and got something out of it. The crazy thing is… this list could be considered incomplete. I left out desmostylians, slingshot deer, that tusked dolphin from New Zealand I learned about at SVP, dwarf mammoths, the weird horns of antilocaprids, the even weirder horns of certain artiodactyl groups, notoungulates, litopterns, moas, haast’s eagle, land crocs, killeroos, mihirungs, brontotheres, creodonts… This list could go on forever.

Despite all i have discussed here, dinosaurs will continue to reign supreme. Even though mammals are every bit as weird and marvelous, size is the only thing that matters. And most dinosaur were larger than the biggest terrestrial mammals (because whales don’t count). But i hope i have shown you a new side to prehistory, one filled with amazing oddities and evolutionary enigmas. Even after 200 years of paleontology, we still have as much to learn about the Cenozoic as we do about the “age of reptiles”.

Till next time!

ps- if you see any typos or misspellings… tough shit. I just spent over 2 months on this and have other stuff to do (going out into the field next week), so proof reading just never happened. Some might say it damages my professional image. But that implies I had one to begin with.