Fanged, Tiny Veggie Dinosaur Found

Though it weighed less than most housecats, this punky dinosaur likely used its bristles to appear bigger.

By Jennifer Viegas
Wed Oct 3, 2012

Skin, scales and quills are added to a cast of the skull of Heterodontosaurus, which was discovered in South Africa. CLICK FOR MORE IMAGES
Tyler Keillor

A "punk-sized" dinosaur with porcupine-like bristles featured some flashy stabbing self-sharpening fangs -- although it likely only had a taste for plants.

The newly identified dinosaur, named Pegomastax africanus, or "thick jaw from Africa," was a mere two feet long and weighed less than a modern housecat in the flesh. Its remains were chipped out of 200-million-year-old red rock from South Africa.

Though small, the dinosaur was a plucky survivor.

"I think the bristles would have made it look at least a little bigger than it was -- perhaps they could poke out more strongly when excited," Paul Sereno, author of a study about the find in the journal ZooKeys, told Discovery News.

PHOTOS: See Images of Pegomastax

"The main defense would be speed of escape," added Sereno, a paleontologist and professor at the University of Chicago. "These were very long-legged fast critters. (They could inflict) a nipping bite if cornered, using the fangs much like a peccary or fanged deer."

Sereno studied the remains, which belong to a single specimen uncovered in a collection of fossils at Harvard University. Sereno has identified it as a heterodontosaur. This group of herbivores included some of the first dinosaurs to spread across the planet.

VIDEO: A recently discovered dinosaur could unearth clues on the early days of dinosaur evolution.

At the time, the supercontinent Pangea had just begun to split into northern and southern landmasses. This led to heterodontosaurs divided into northern species with simple triangular teeth, and southern species, like Pegomastax, with taller tooth crowns.

Pegomastax had 1-inch-long jaws that supported a short, parrot-shaped beak up front, a pair of stabbing canine teeth, and tall teeth tucked behind. The teeth in the upper and lower jaws operated like self-sharpening scissors, with shearing wear facets that slid past one another when the jaw was closed.

Sereno believes the less than 3-inch-long skull was probably adapted to plucking fruit, and not to ripping flesh out of animal prey. This is supported by the way the teeth met during a bite, their shape, and wear pattern.

Given that the wear facets in this and related dinosaurs are "blunt with broken shards…this would not be good for a meat eater and suggests the teeth were more for digging or rooting around and in nipping competitions or occasional defense than in acting like steak knives necessary for feeding on a daily basis."

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With its bristles, Pegomastax looked something like a "nimble two-legged porcupine," according to Sereno. Similar bristles first came to light in another comparable sized heterodontosaur called Tianyulong from China. The bristles spread across its body from the neck to the tip of its tail.

As for the term "punk," Sereno explained that he prefers that description over the word "dwarf," since "dinosaurs started out small (and) we tend to forget that."

He added, "These plant-eaters are among the very oldest we know from the bird-hipped side of the dinosaur tree. They started out small, and some of them got a bit smaller to be among the smallest dinosaurs we know."

While it's unknown what carnivores might have feasted on Pegomastax, this tiny dinosaur lived in an ecosystem with a much larger plant-eater, Massospondylus, and its kin. Some of these dinosaurs weighed at least a ton.

Hans-Dieter Sues, a senior research geologist and curator of vertebrate paleontology at the National Museum of Natural History, agrees Pegomastax was a highly specialized plant-eating dinosaur.

"Of course, it is always important to remember that most plant-eaters will occasionally avail themselves of animal protein to meet metabolic needs," Sues added. "Pegomastax belongs to a group of distinctive, small bird-hipped dinosaurs that appeared surprisingly early in the evolutionary history of dinosaurs."

Sereno, founder of Project Exploration, said he is inspired to study dinosaurs and to make models of them "for the next generation, who are now kids." His own imagined ponderings about Pegomastax compelled him to test out various possibilities before coming to the conclusions.