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| With jaws only one inch
in length, the plant-eating Pegomastax is one of
the smallest dinosaurs ever discovered |
Oct. 3: Not every dinosaur grew up to be a mighty predator like Tyrannosaurus rex or a hulking vegan like Apatosaurus.
A few stayed small, and some of the smallest dinosaurs that ever lived — tiny enough to nip at your heels — were among the first to spread across the planet more than 200 million years ago. Fossils of these miniature, fanged plant-eaters known as heterodontosaurs, or “different toothed reptiles”, have turned up as far apart as England and China.
Now in a discovery that has been at least 50 years in the making, a new and especially bizarre species of these dwarf herbivores has been identified in a slab of red rock that was collected in the early 1960s by scientists working in South Africa.
In a report published today in the online journal ZooKeys, Paul C. Sereno, a paleontologist at the University of Chicago and a dinosaur specialist, described the strange anatomy of the new-found member of the heterodontosaur family and gave the new species the name Pegomastax africanus, or “thick jaw from Africa”.
He also apologised in an interview for not getting around sooner to this piece of research.
When he first viewed the specimen at a Harvard laboratory, Sereno said: “My eyes popped, as it was clear this was a distinct species.”
Embedded in the rock were remains of a creature with a short parrot-like beak, one-inch jaws, sharp teeth and a skull no less than three inches long. The entire body was less than two feet in length and probably weighed less than a small house cat.
“I’m embarrassed to say how many years ago that was — 1983,” he said. “But I was an enterprising graduate student then at the American Museum of Natural History. All the while since then, I wondered if anyone else might spot the creature hiding among the lab drawers.”
The Pegomastax fossils were eventually returned to the South African Museum in Cape Town, the true nature of the one slab still undiscovered. The main researcher responsible for collecting the fossils was Alfred Crompton, a Harvard professor now retired. Part of Sereno’s research was supported by the National Geographic Society.
His close examination showed that behind the parrot-shaped beak were a pair of stabbing canines up front and a set of tall teeth tucked behind for slicing plants. These teeth in upper and lower jaws operated like self-sharpening scissors, Sereno said, with shearing wear facets that slid past one another when the jaws closed. The parrot-like skull, he noted, may have been adapted to plucking fruit.
Sereno said it was “very rare that a plant-eater like Pegomastax would sport sharp-edged enlarged canines”. Some scientists suggested that the creature may have consumed some meat, or at least insects.
But Sereno concluded that the creature’s fangs, unusual for a herbivore, were probably “for nipping and defending themselves, not for eating meat”.
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