Nature does pretty and nature does ugly. And sometimes it does really, really ugly. Never was that truer than 200 million years ago when the Pegomastax africanus was walking — or scurrying — the Earth. The critter was a whole new kind of homely, but judging by a paper just published simultaneously in the online journal Zookeys and on the National Geographic Society website, it was a whole new kind of cool too. The little cat-sized beast is a vivid example of how evolution can sometimes assemble the most unlikely body types out of what amounts to off-the-shelf parts — and make them work improbably well together.
Before the new paper was released, the Pegomastax species had never been named or even fully described, but that doesn’t mean that the discovery of its remains is remotely new. The first specimen of the animal was found in a rock outcropping in Africa in the 1960s. It was dug out and shipped to the U.S., where it spend the better part of the past five decades in the paleontology collection at Harvard University. The fossil seemed like nothing special — the remains of just one more small, scurrying herbivore that inhabited a world in which the thundering allosaurs and Tyrranosaurs were the true stars. It wasn’t until last year that Paul Sereno, a professor of paleontology at the University of Chicago and National Geographic explorer in residence at Harvard, got a look at the fossil, and realized he had something unusual in his hands.
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The animal had a head like a vulture and a beak like a parrot, with tall, sharp teeth near the back of its mouth. The beak was apparently designed for plucking fruit and the teeth for slicing and tearing leaves and other plant matter. Wear patterns on both the top and bottom teeth indicate that they scraped against each other as the jaw opened and closed, which may or may not have been pleasant for the Pegomastax —whose name, appropriately, means “thick jaw” — but it did keep the teeth freshly sharpened at all times. This kind of jaw design is not uncommon for small herbivorous dinosaurs, but the Pegomastax had one feature that set it apart from most of the others: a pair of stabbing canine teeth in front of the slicing teeth — standard equipment for a meat-eater sure, but definitely not for a birdlike plant-eater.
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“It would take ornithischian dinosaurs millions of years—not until the Early Cretaceous around 130 million years ago—to develop scissors like self-sharpening dentitions as sophisticated as [these],” Sereno wrote in an e-mail to Time. “And none ever re-evolved such fangs! I would suggest, modestly, that Pegomastax would make a good Halloween mask.” But apart from simply making it the scariest beast on the block, what was a bird-headed dinosaur doing with such teeth?
A very small handful of similar fossils have tuned up with the same mix of both carnivorous and herbivorous teeth — enough that the genus has been given a name: Hederodontosaurus, which means, straightforwardly enough, different-toothed lizard. Paleontologists have speculated that the animals within the genus perhaps supplemented their vegetable diet with insects or even larger bits of meat, but in the case of the Harvard specimen at least, Sereno disagrees. Chips and scrapes in the enamel layer of the teeth suggests they were used not for eating but for biting when fighting, which would have been necessary both in competing for mating opportunities with other members of the species and in battling predators.
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One thing that did not survive the long-ago fossilization process but was likely a part of the living Pegomastax was a covering of bristles, very much like those of a porcupine. A recent fossil unearthed in China bears a close enough similarity to the Harvard specimen that it is thought to be the same species or at least closely related. Those bones were found buried deeply in lake sediment and that provided enough protection that the bristle coat remained.
“Some have said [the bristles] are related to feathers, but I do not believe this,” Sereno wrote. “They do not branch or split, which is a key feature of feathers. Other ornthischians have scales, and once you have feathers over your body, you cannot at the same time have scales. Bristles don’t look to be good insulators; rather they made the animal look bigger than it was and may have been brightly colored.”
Despite its apparent toughness, the Pegomastax and its larger genus were not built for survival. The most advanced Heterdontosaurs vanished about 150 million years ago, Sereno says, just as the Jurassic period was ending. “Perhaps they were too specialized for their own good,” he speculates. “Changing climate and plant life may have done them in.” And in the case of these animals, dead really does mean dead. Many species that survived up to the great dinosaur die-off 65 million years ago were at least able to push their genes across the extinction boundary, where they were partly subsumed into the genome of modern birds. Not the Heterodontosaurs. The parrot’s beak and the porcupine’s quills may resemble those of the old Pegomastax, but they were in fact tricks evolution had to learn all over again. The progenitor animal — as clever as it was ugly — is gone forever.
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