New fanged dwarf dinosaur from southern Africa, ate plants

October 3, 2012
This shows the new dinosaur dwarf Pegomastax from South Africa. With jaws only 1-inch in length, plant-eating Pegomastax ("thick jaw") is one of the smallest dinosaurs ever discovered. Credit: Drawing by Todd Marshall

With tiny 1-inch long jaws, a new species of plant-eater has come to light in rocks in southern Africa dating to the early dinosaur era, some 200 million years ago. This "punk-sized" herbivore is one of a menagerie of bizarre, tiny, fanged plant-eaters called heterodontosaurs, or "different toothed reptiles", that were among the first dinosaurs to spread across the planet.

The single specimen of the new species was originally chipped out of red rock in in the 1960's and discovered in a collection of fossils at Harvard University by National Geographic Explorer-in-Residence Paul Sereno, and professor at the University of Chicago. Details of the dinosaur's anatomy and lifestyle are part of a monograph by Sereno dedicated to these puny herbivores and published in the online journal ZooKeys and on the website of the National Geographic Society.

Named Pegomastax africanus, or "thick jaw from Africa", the new species has a short parrot-shaped beak up front, a pair of stabbing canines, and tall teeth tucked behind for slicing plants. The tall teeth in upper and lower jaws operated like self-sharpening scissors, with shearing wear facets that slid past one another when the closed. The parrot-shaped skull, less than three inches long, may have been adapted to plucking fruit.

This is a Heterodontosaurus flesh model and skull. Skin, scales and quills are added to a cast of the skull of Heterodontosaurus, the best known heterodontosaurid from South Africa. Credit: Photo and sculpting by Tyler Keillor.

"Very rare", admits Sereno, "that a plant-eater like Pegomastax would sport sharp-edged, enlarged canines" like that of a vampire. Some scientists have argued that consuming meat or at the least insects was a good part of the diet of heterodontosaurs, which evolved near the root of the great bird-hipped radiation of that includes the famous plant-eaters and Stegosaurus.

Self-defense and competitive sparring for mates is more likely their role, argues Sereno in the study, based on of the teeth of Pegomastax and kin. Wear facets and chipped enamel suggest that the of Pegomastax and other heterodontosaurs were used like those of living fanged deer for nipping or even digging rather than slicing flesh.

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This shows the making of the Heterodontosaurus flesh model. Muscles, skin, scales and quills are added to a skull cast of Heterodontosaurus. Credit: Video and sculpting by Tyler Keillor

A bizarre covering of bristles, something like that of a porcupine, likely covered most of the body of Pegomastax, which measured less than two-feet in length and weighed less than a housecat. These bristles first came to light in a similar-sized heterodontosaur, Tianyulong, discovered recently in China and described in the study. Buried in lake sediment and covered by volcanic ash, Tianyulong preserves hundreds of bristles spread across its body from its neck to the tip of its tail. In life, dwarf-sized heterodontosaurs like Pegomastax would have scampered around in search of suitable plants, says Sereno, looking something like a "nimble two-legged porcupine".

When Pegomastax lived some 200 million years ago, the supercontinent Pangaea had just begun to split into northern and southern landmasses. Heterodontosaurs appear to have divided similarly, the study argues, the northern species with simple triangular teeth like Tianyulong and the southern species with taller crowns like Pegomastax.

Sereno marvels at these punk-sized early that spread across the globe. Although virtually unknown to the public, "Pegomastax and kin were the most advanced plant-eaters of their day".

Explore further: Sands of Gobi Desert yield new species of nut-cracking dinosaur

More information: Sereno PC (2012) Taxonomy, morphology, masticatory function and phylogeny of heterodontosaurid dinosaurs. ZooKeys 224: 1-225. doi: 10.3897/zookeys.224.2840

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1.4 / 5 (9) Oct 04, 2012
Very interesting, and unusual. It seems that these dinosaurs had developed a trait thought to be unique to mammals. Perhaps the canine teeth were used for fighting. There are certain herbivorous mammals that use their canine teeth for conflict (horses, camels, wild boars, hippos and deer). Although, they're usually larger in males. There's no doubt about it, though - there is some remarkable diversity shown in dinosaurs.
3.2 / 5 (22) Oct 06, 2012
thought to be unique to mammals. Perhaps the canine teeth were used for fighting.
What is that, teeth? Most dinos had teeth. And canines are used to kill prey. That's pretty common knowledge.

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