Saturday, November 19, 2016

Avimimus portentosus by Apsaravis

Avimimus, meaning “bird mimic” (Latin avis = bird + mimus = mimic), was a genus of oviraptorosaurian theropod dinosaur, named for its bird-like characteristics, that lived in the late Cretaceous in what is now Mongolia, around 70 million years ago.

As its name clearly suggests Avimimus was a very birdlike dinosaur. It was a lightly built, long-legged animal that may have made its living by chasing after small reptiles and mammals. Avimimus’s diet is still a subject of debate; some scientists believe that it probably fed mainly on insects. It was capable of swift speeds, which would have both enhanced its efficiency as a predator and helped it to avoid falling prey to larger meat-eating dinosaurs.

Size of A. portentosus compared to a human

Avimimus was a strange-looking dinosaur. It had a long neck and a short head with a tooth-less mouth. It had a large braincase, which suggests that its brain, too, was relatively large. In place of teeth it had a powerful beak, similar to that of a present-day cockatoo. The bones of its wrist were fused together as they are in birds and the three long fingers could be held tucked under the body. In fact, Avimimus could fold its whole arm against its body in a similar fashion to the way a bird folds its wing.

Its long legs ended in three toes, with a smaller fourth toe nestled on the inside of the foot. All the toes and fingers were tipped with sharp, curved claws. Unlike a bird, however, Avimimus had a long, bony tail and its pelvis resembled those that are seen in other theropods. It is possible that Avimimus had feathers of some kind, but the deposits in which it has been discovered are too coarse for such features to have been preserved. However, a rough ridge on the forearm of Avimimus – similar to the one on Caudipteryx, which supported a half-wing – may well have served to anchor feathers. However, even if Avimimus did have feathers, it seems unlikely that it would have been capable of flight.

We have known about Avimimus for only a relatively short time. Russian expeditions into Mongolia in the late 1970s and early 1980s were the first to discover fossils of it, and it was described and named only as recently as 1981. Since then, Chinese paleontologists have unearthed other fossils, but remains of Avimimus are still very rare. Only three partial skeletons – and no complete skeletons – have so far been discovered.