Thursday, 4 October 2012

A Bizarre New Species Of Dinosaur

Dinosaurs are the most well known group of prehistoric beasts on Earth. Anyone over the age of four will recognize the name of Tyrannosaurus rexStegosaurus or Velociraptor. Some may even come across Ankylosaurus or, if they are particularly intrigued, Pachycephalosaurus. Dinosaurs were some of the most diverse reptiles on Earth, coming in all shapes and sizes with a bewildering array of ornaments.

The skull and a restoration of Pegomastax africanus
Styracosaurus sported a head full of sharp spikes and frills, Microraptor had four feathered arms which doubled as wings and Incisivosaurus possessed two buck teeth which stuck out at the front of a beak-like jaw. There are many weird and wonderful examples of these long extinct reptiles from across the globe, but a recent fossil discovery from Africa may well trump them all. 50 years ago, a skull was recovered from red Triassic rocks near Lesotho in South Africa.

Like so many important finds, it languished in the backrooms of a museum, in this case Harvard, until Paul Sereno, a palaeontologist from the University of Chicago stumbled upon it. It was immediately clear that it was something new. By the end of his analysis, he had come up with a creature which, to put things simply, would have looked like a vampire fanged, parrot beaked, two legged, reptilian porcupine the size of a house cat weighing in at less than 7 kilograms.

Of course, scientific names often reflect the characteristics of their organism. Tyrannosaurus rex translates as 'tyrant lizard king,' apt considering its nature as a top predator. Despite all of this newcomer's odd features, it was given the rather colloquial name of Pegomastax africanus which translates as 'thick jaw from Africa.' Yet, while its name is ordinary, its revelations about the evolution of dinosaurs is not.

A comparison between an adult human and Pegomastax africanus
Its closest relative is a creature called Tianyulong discovered in the remains of an ash-choked lake bed. This creature possessed porcupine-like quills, suggesting that Pegomastax also had such features. Yet the quill, in both species, were quite weak. It is unlikely that that they were used for insulation (both creatures lived in warm climates). Instead the quills were probably used for making their owner look larger, to ward off predators.

Its skull was also a mine of information. Its size showed that it was not a carnivore and while it was nimble, it was still not fast enough to catch insects. The beak was most likely used to nip off and crack open nuts and seeds. While the fangs on the other hand were not sharp, but slid past each other as the jaws closed, creating a slicing surface akin to a pair of scissors. These would have been perfect in cutting through everything from tough, fibrous plant stems to leaves.

Yet the real discovery comes when the creature is placed in the tree of life. Pegomastax is close to the base of the ornithischians, one of the two main groups of dinosaurs, the other being the saurischians. The two groups split away from each other during the early Triassic. Current analysis suggests that Pegomastax played a very important part in this event.

The empire of the dinosaurs stretched from the seasonal north to the deserts on the equator for nearly 200 million years. What remains of this empire now lies beneath our feet, ground down into the soil or entombed in the rocks of the continents. Our knowledge of dinosaurs increases daily, bringing their lost world into the light.