Fun with Liquid Nitrogen

Meanwhile on land during the Eocene epoch, the terror bird was meeting up with some fierce competition for the limited open grasslands. Carnivorous mammals have finally reached apex predator status! No more hiding in the trees and in burrows for these mammals. And here he is, arguably the largest mammalian land predator of all time:

We’ve only ever found one skull of Andrewsarchus, a monstrous 2.7-foot long skull resembling the skull of a carnivore ( For contrast, a modern lion’s skull is about 15 inches long and the extinct great cave bear’s skull is 21 inches). Based on creatures of the time with similar skulls, such as Mesonyx and Synoplotherium, scientists can infer what Andrewsarchus might have looked like and how large it was. Estimates place Andrewsarchus at about 6-6.6 feet at the shoulder and 11-17 feet long, not including the tail. The weight of Andrewsarchus could be anywhere from 1,000-2,000 pounds. We don’t know for sure because Andrewsarchus might have been a slender, gracile creature or stocky and compact like a bear. At any rate, it was a monster predator the size of a rhino, if not as heavy.

There is of course, debate on whether Andrewsarchus was a loathsome scavenger or an admirable hunter, but as I’ve said before, very few animals are obligate hunters and nearly every carnivorous mammal that has ever lived will do whatever it takes to survive, whether it be hunting or scavenging. They don’t care about impressing you. Most hunt or scavenge depending on the opportunity they face at any given time. I think it’s a silly debate.

When I first saw some pictures of Andrewsarchus, I thought it was a massive prehistoric hyena. It turns out though, that Andrewsarchus was not related to hyenas at all. It couldn’t be- the order Carnivora was only just beginning to evolve from their ancestral family Miacidae. It would be a few more million years before large Carnivores appeared on the scene.

So Andrewsarchus was a carnivore but not a Carnivore. The way to make sense of this is to understand that an animal can hunt or scavenge other animals and be carnivorous, but not of the official Order Carnivora, which includes all hyenas, cats, wolves and other canids, seals, weasels, and some offbeat members like the civet and the otter.

One way that Andrewsarchus was similar to Carnivores was that he appeared to have carnassial teeth. Nearly all Carnivores have them- they’re the cheek teeth in front of the molars on the upper and lower jaw that occlude in a special way to ensure maximum crushing and shredding. Dogs are no exception. If you ever need to stick your hand in a dog’s mouth for any reason- maybe he’s like my dog and has a tendency to get tennis balls stuck in his throat- you need to be sure to enter only from the front and NEVER take a lateral approach. In front, you have some incisors and some canines, but if you put your hand between a dog’s carnassial teeth, you may not have much of a hand left afterward. If you’ve ever seen a dog or a hyena chew on a grisly bone, you might have noticed that they don’t use their canines or incisors to shred and crush it. They’re always chewing on it from the side. Andrewsarchus probably crushed and chewed bones the same way.

So if Andrewsarchus was not a Carnivore, what was he?

The short answer is that he was kinda-sorta a pig. An ungulate. Most likely the scariest thing with hooves the world has ever known. He was of the order Mesonyx, of which all members are now extinct. This order was a group of wolfish, carnivore-like hoofed mammals, somewhat related to pigs and ruminants. You can see his family tree here:

Andrewsarchus’s order is in the third column, center- Mesonyx. I found this family tree pretty interesting. You can see that also in the third column on the top we have Pakicetus, who was an ancestor of our friend Ambulocetus- as you can see, their kind evolved into the modern walvis, who also share some ancestry with modern zwijn and other hoofed mammals. He’s even related to the unfortunate paard, who always seems to be getting eaten.

Despite being a hoofed mammal, though, Andrewsarchus didn’t show any family loyalty to horses, the most delicious prey animal of the Paleogene period. Things still aren’t looking so good for horses.

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