(host) A showdown took place on the plains of Wyoming some 34 million years ago. For weapons, the fighters had only their strong teeth and strange powerful jaws. Walking on cloven hooves, they sized each other up until finally one of them lunged. It sank its teeth into the face of its rival, carving deep scars into its snout and around its eye sockets. It even left a bite wound on the roof of its opponent's mouth and crushed the sinus cavities in its skull. We don't know how this fight ended, but we know that it happened and that it wasn't an isolated incident. These ancient foes were animals known as Archaeotherium, members of a fascinating group of mammals called the entelodonts. Because they were thought to look vaguely like some kind of nightmarish hogs, entelodonts have been given one of the coolest nicknames in all of paleontology-- the "hell pigs. But despite the name, we don't know where these so-called hell pigs belong in the mammalian family tree. In fact, once you get a close look at them, you see that they don't look that much like pigs. If anything, they look kind of like a bunch of other animals put together. They walked on hooves like pigs do, but they had longer legs almost like deer, and they had hunchbacks a bit like rhinos or bison, and everything above the neck on these animals was just strange-- huge canine teeth, ridiculously big heads and cheekbones that were just, what? But as is often if not always the case, there is some evolutionary method to this anatomical madness. The seemingly strange anatomy of the hell pigs can actually help us understand their behavior and lifestyles and lend insights into the competitive environments in which they lived. Unlike the true pigs we know today, these creatures were at times fierce hunters, resourceful foragers, canny scavengers, and not above turning on each other to fight over food, territory or sex. Their fossils tell a tale of hard times and sometimes hellacious lives that made them truly worthy of their hellish nickname.

(Describer) Title: Eons.

Nobody knows what the entelodonts evolved from. The first of them appear abruptly in the fossil record of China and Mongolia about 40 million years ago around the middle of the Eocene Epoch. But we do know that these earliest species like Eoentelodons were artiodactyls-- even-toed ungulates that today include deer, hippos, and pigs. And paleontologists haven't figured out what their closest living relatives are. But according to two recent studies that compare the anatomies of a wide range of artiodactyls, entelodonts may be more closely related to hippos and whales than they are to pigs, because yes, whales' ancestors were themselves hoofed mammals that once walked on land. Now by 35 million years ago, some entelodonts, like brachyhyops, had dispersed from Asia and into North America. And before long, hell pigs on both sides of the Pacific started to get big--like, just really big. In Eurasia, there was entelodon, whose range stretched from Japan to France and stood about 1.3 meters high at the shoulder. Similar in size and shape was Archaeotherium, which stalks North America from 34 million to about 25 million years ago. And just like entelodonts, it had a huge geographic range. Fossils of Archaeotherium had been found as far north as Saskatchewan and as far south as Texas. And as these hell pigs got larger and more widespread, they began to develop perhaps their most peculiar trait, long, massive skulls. The skull of Archaeotherium, for example, was a little under 60 centimeters long, more than a quarter of the animal's entire length, but the largest of the entelodonts was daeodon. This hulking beast was more than two meters tall at the shoulder and may have weighed almost half a ton and its head was almost a meter long-- 35% of his total body length. Now if you've got a big giant head, then you need some sizable muscles to support it, which probably explains another eye-catching feature of the entelodont anatomy and many of the later hell pigs. The tall bony projections on the backs of their vertebrae called neural spines were unusually long near the shoulders, creating a kind of pump. These spines probably served as attachment points from the powerful muscles that held up the creatures giant heads. Now, even though the hell pigs had huge skulls, their brain cases were pretty small. And judging by the contours of this cavity, scientists think they may have had big olfactory lobes, suggesting that they had an acute sense of smell. But the true purpose of the entelodonts' giant heads might just have been that they allowed the hell pigs to eat pretty much anything they wanted, and proof of that is in their teeth. Entelodonts had long incisors, sturdy canines, and sharp, serrated premolars. And they had blood square molars that are the hallmarks of a true omnivore. But we talked to an expert in hell pig research, Dr. Scott Foss of the U.S. Bureau of Land Management, and he pointed out to us that the weird thing about entelodont teeth is that they were coated in a layer of enamel that he described as freakishly thick. And with these well-protected teeth, Dr. Foss said, entelodonts could probably crack open bones like today's hyenas do. Now if you're going to bite through bones, then you need some powerful jaw muscles, and the hell pigs most certainly had those. Okay, put your fingers on your temples and bite down a couple of times. What you feel moving around are your temporalis muscles. They start on the sides of your skull, pass under your cheekbones, and attach to the lower jaw. Now entelodonts had absolutely massive cheekbones that stuck out the sides of their faces, and paleontologists think that these features allowed for some truly huge jaw muscles, which gave the animals incredibly strong bites. So unlike some other artiodactyls, which developed specialized teeth for eating different kinds of plants, it seems that the hell pigs ate whatever they can find from plant matter like roots, nuts, and fruit to carry in, and maybe even live prey. For example, in Eastern Wyoming, there's a 33 million-year-old bone bed that includes the jumbled skeletons of small American camels known as Poebrotherium, and the camel skulls, necks and ribs are covered in bite marks that line up precisely with the teeth of Archaeotherium. So some paleontologists have suggested that the hell pigs chased down a bunch of these little camels and dragged them back to the site to eat later, creating a sort of ancient meat locker. Scientists have also recovered fossils of chalicotheres and rhinos with bite marks on them that again perfectly match the teeth of entelodonts, which could be evidence of scavenging, predation or both. And as we saw in that ancient showdown in Wyoming, the hell pigs were also known to go after each other-- not as prey, but as rivals. In 2001, Dr. Foss and his colleagues reviewed 170 hell pig skulls and found that at least 7% of them had healed bite marks on their snouts and faces. Based on their shape and placement, these wounds were most likely made by other entelodonts in competition over mates, food, or territory. And in combat, too, those powerful jaws probably came in handy. Paleontologists have found that hell pigs could open their mouths really wide-- as much as 109 degrees in Archaeotherium. This enormous gape would have not only helped in eating big, hard foods like roots, but it also would have allowed the entelodonts to jaw wrestle, lunging at opponents with open mouths, much like hippos do today. After millions of years of hard living, the last of the entelodonts died out about 17 million years ago in the Miocene Epoch, and the reasons for their extinction remain a bit mysterious because animals like hell pigs that could eat almost anything are usually quite good at adjusting to environmental changes. Part of their downfall might have been fueled by competition, like from the up and coming carnivores known as the bear dogs. And in some places were hell pig fossils have been found, scientists have observed an interesting pattern. At two fossil sites in South Dakota and Nebraska, large numbers of entelodonts have been found at features that appear to be watering holes that dried up. We know that droughts became much more common in the middle Miocene as the climate of North America became drier. So it could be that hell pigs were especially vulnerable to droughts, and that many of them met their end waiting for rains that would never come. And yet they persisted for 25 million years, leaving behind their strange remains that hinted an equally odd mixture of adaptations and behaviors. Like bears and pigs, they probably ate almost anything from roots to meat. Like rhinos, they use their specialized backbones to hold up their giant heads. They fought like hippos, and like hyenas, they had heavily enameled teeth that they could have used to crack open bones. In the end, life is never easy for any organism, but the hell pigs turned out to be well equipped enough to survive millions of years of hard times, from periods of drought to showdowns on the High Plains. Accessibility provided by the U.S. Department of Education.

(Describer) Title: PBS Digital Studios. Accessibility provided by the US Department of Education.