Family Ceratosauridae

This family of megalosaur-type dinosaurs was characterized by a small horn on the snout. Contemporaries of the other large carnosaurs, they lived in North America and East Africa in Late Jurassic times. But their remains are rare in comparison to those of their relatives.

name: Ceratosaurus time: Late Jurassic locality: North America (Colorado and Wyoming) size: 20 ft/6 m long

This "horned lizard" had a heavier skull than other carnosaurs because of the presence of a pair of bony ridges above its eyes, and a low crest, or horn, on its snout.

The function of the horn remains a mystery, although various suggestions have been put forward as to its use. It could have been used for defense, but it seems too small and not well placed for a fight. Or it could have been for sexual display, with only the males possessing it and using it in the ritualistic, headbutting battles probably engaged in to decide hierarchy among the group.

Ceratosaurus was evidently an active predator. It had massive jaws, armed with sharp, curved teeth. The short arms had 4 powerful, clawed fingers, and the long legs had 3 clawed toes on each foot. An unusual feature was a narrow row of bony plates running down the center of its back and tail, giving the appearance of a serrated crest. This could have been a device for losing heat from the body, similar to the back fin of Spinosaurus (see p. 120) or the plates of Stegosaurus (see p. 156).

Footprints thought to be those of Ceratosaurus have been preserved in the dinosaur-rich rocks of the Morrison Formation in the western USA. These ancient trackways suggest that these dinosaurs moved in groups, and maybe cooperated in packs to bring down the larger dinosaurs.

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