Segnosaurus showed an unusual combination of features of ornithischians, theropods and prosauropods. Its pelvis looked like the pelvis of the dromaeosaurids, although it was much larger. Segnosaurus had feet with long, slender theropod-like claws and ankles, although it had four toes instead of three on each foot. The teeth, although there were many and small, resembled those of some theropods.
We know of only a few remains of Segnosaurus, but the whole animal can be restored by comparison with its close relatives. The head is based on the skull of the closely related Erlikosaurus, and the feathery covering comes from an early Cretaceous form, Beipiaosaurus, found perfectly preserved in the Liaoning sediments, in China.
Name: Segnosaurus, meaning ‘slow reptile’
Size: 4-9m long
Food: probably plants, but some experts have suggested meat and fish
Lived: 75 million years ago in the Late Cretaceous Period in Mongolia
The fragmentary remains of this genus show the typical down-turned jaw with the leaf-shaped teeth, and the hip bones with the swept-back pubis that give the impression of an ornithischian dinosaur. These are important details in establishing the makeup of this whole line of dinosaur. It is such an important animal that the name Segnosauria has been proposed as alternative name for the group. Fossil eggs about the size of duck eggs have been attributed to these animals.
Experts are not sure what sort of food Segnosaurus ate. It had teeth at the back of its jaw to cut up food – like the bipedal carnivores. But at the front of its mouth was a toothless beak – like some of the herbivores. Indeed, the dinosaur was probably omnivorous.
Segnosaurus also had feet quite unlike those of ordinary carnivores. It had sturdy legs and short, broad feet which ended in four toes. Some experts think that the feet may have been webbed.
The scientist who named Segnosaurus in 1979 suggested that it waded, or even swam, catching fish with its claws or in its toothless beak. But scientists are still unsure; it is possible that it was a herbivore and used its beak to nip off leaves.
The restoration is largely based on the partial remains of three skeletons. It differs from other therizinosaurids by the arrangement of teeth in the jaw.