Family Psittacosauridae

The "parrot" dinosaurs were a rare group of ornithischian dinosaurs, found only in the Early Cretaceous rocks of East Asia. Their skulls show many features that suggest that they were the ancestors of the horned dinosaurs, or ceratopians. Their bodies, however, were similar to those of the gazellelike* hypsilophodonts, from which stock they probably arose (see pp. 138-141).

Like the hypsilophodonts, the parrot dinosaurs could rise up on 2 legs to run away from predators. The suggestion, therefore, is that the early ceratopians, descended from the parrot dinosaurs, were also bipedal, and only reverted to a 4-legged stance later in their evolution.

name: Psittacosaurus time: Early Cretaceous locality: Asia (China, Mongolia and

Siberia) size: up to 8 ft/2.5 m long A square skull and a horny, toothless beak are the features that have given this

Asian dinosaur its name — Psittacosaurus, meaning "parrot lizard."

A thick ridge of bone on the top of the skull squared off the head at the back. This ridge served as an anchor point for the muscles of the powerful lower jaws. Over millions of years, it was to develop into the great, bony neck frill of the later ceratopians.

The cheek bones of Psittacosaurus were drawn out into a pair of hornlike projections. These were the forerunners of the horny spikes that grew out from each side of the head shield of later ceratopians.

The ancestor of the ceratopian group is believed to be among the parrot dinosaurs. But it is unlikely to be Psittacosaurus itself, since this animal had only 4 fingers on each hand, while the ceratopians had 5; also, Psittacosaurus had no teeth in its beak, while the early ceratopians, the protoceratopids (below), had teeth in the upper beak.

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