Dinosaur classification

When paleontologists hear that a dinosaur egg has a baby inside, the first thing they want to know is 'What kind of dinosaur is it?' As you will have seen, at least some of these Chinese eggs contain a dinosaur which has been identified as a 'therizinosaur' - but what is a therizinosaur? Dinosaurs are divided into two main groups. The Ornithischia (or 'birdhipped dinosaurs) include many well-known forms such as the armored stegosaurs and the horned ceratopsians, as well as Iguanodon. The second group is called the Saurischia (or 'lizard-hipped' dinosaurs). This group contains the sauropodomorphs and the theropods. The first includes some very early dinosaur forms, known as prosauropods, and gigantic sauropods. The theropods were carnivorous forms, and included Tyrannosaurus and Velociraptor. Theropods are of particular interest because they are thought to be the group which gave rise to birds. It is very unclear where therizinosaurs fit into the classification of the dinosaurs. Some paleontologists believe that therizinosaurs are sauropodomorphs. More recently several researchers have found evidence that suggests that they were unusual theropods. The issue is still controversial and it may be that the baby therizinosaurs in this exhibition will help settle this argument.

What sort of animals were therizinosaurs?

Therizinosaurs are bipedal dinosaurs which have been discovered in the Middle and Late Cretaceous rocks of China (PRC) and Mongolia. They were medium-sized forms, reaching lengths up to 4 meters. Their skulls are rather unusual, possessing a well-developed toothless beak at the front end of the jaws, and many small, leaf-shaped, serrated teeth further back. The hands and feet seem to have been equipped with very large and sharp claws. We do not fully understand what therizinosaurs ate or how they lived, although most other fossil and recent reptiles with similar teeth are plant-eaters.