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New plant-eating dwarf dinosaur discovered - Pegomastax africanus

By Adrian Bishop - 03 Oct 2012 13:0:0 GMT
New plant-eating dwarf dinosaur discovered - Pegomastax africanus

With jaws only 1-inch in length, plant-eating Pegomastax ("thick jaw") africanus is one of the smallest dinosaurs ever discovered; Credit: © Todd Marshall

A 'punk-sized' dwarf dinosaur that ate plants has been discovered from fossils in South African rocks.

The plant-eater had tiny fangs and jaws just 2.5cm (1in) long and are part of the heterodontosaurs (different toothed reptiles) that were among the first to roam the planet 200 million years ago.

The new species, named Pegomastax africanus, or 'thick jaw from Africa' had a short parrot-shaped beak, two stabbing canines and tall teeth behind for slicing plants. The teeth in the upper and lower jaws worked in a similar way to self-sharpening scissors. The parrot-shaped skull that is under three inches long could have been adapted to picking fruit.

The fossils were first found in red rock in South Africa in the 1960s and found in a collection at Harvard University by palaeontologist Paul Sereno, professor at the University of Chicago and National Geographic Explorer-in-Residence.

Details about its anatomy and lifestyle are part of a monograph in the online journal ZooKeys.

Some heterodontosaurids, such as South African Pegomastax or Chinese Tianyulong (shown here), grew to less than 2 feet in length and rank as dwarfs in the dinosaur era

Some heterodontosaurids, such as South African Pegomastax or Chinese Tianyulong (shown here), grew to less than 2 feet in length and rank as dwarfs in the dinosaur era; Credit: © Paul Sereno and Carol Abraczinskas

Paul Sereno says it is "very rare that a plant-eater like Pegomastax would sport sharp-edged, enlarged canines" like a vampire.

Some scientists say eating meat was a major part of the diet of heterodontosaurs that evolved near the root of the great bird-hipped radiation of dinosaurs that included the well-known plant-eaters Triceratops and Stegosaurus.

Their role was more likely to be more used in self-defence and competitive sparring for mates, says Paul Sereno, based upon detailed examination of the teeth of Pegomastax and their kin. Wear facets and chipped enamel point to the fact that the fangs of Pegomastax and other heterodontosaurs were used in a similar way to present-day fanged deer to nip or dig rather than slice flesh.

A strange layer of bristles, similar to a porcupine, may have covered most of the body of Pegomastax, which was under two-feet long and weighed less than a modern-day domestic cat.

These bristles were first linked to a similar-sized heterodontosaur, Tianyulong, discovered recently in China and described in the research. The Tianyulong fossil was buried in lake sediment and covered by volcanic ash.

Skin, scales and quills are added to a cast of the skull of Heterodontosaurus, the best-known heterodontosaurid from South Africa

Skin, scales and quills are added to a cast of the skull of Heterodontosaurus, the best-known heterodontosaurid from South Africa; Credit: © Erin Fitzgerald, sculpting by Tyler Keillor

The sediment preserved hundreds of bristles spread from its neck to its tail.

Small heterodontosaurs like Pegomastax would have run around looking for plants, says Paul Sereno and resembled a nimble two-legged porcupine.

When Pegomastax roamed the Earth, the supercontinent Pangaea had begun to split into northern and southern landmasses. Heterodontosaurs seems to have divided in a similar way, says the study. Northern species like Tianyulong had simple triangular teeth and southern species like Pegomastax had taller teeth.

Paul Sereno says the small early herbivores that spread across the globe were impressive and Pegomastax and kin were the most advanced plant-eaters around.

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Topics: Fossils / Dinosaurs