Ceratosaurus

When we think about the theropod dinosaurs, we generally tend to focus on the more famous members of this group of carnivores (meat eaters), such as Tyrannosaurus, or possibly Allosaurus and Albertosaurus. One theropod dinosaur that often gets unjustly overlooked is Ceratosaurus.

The InfraOrder Carnosauria (the "flesh lizards") were some of the largest terrestrial carnivores. This InfraOrder is further divided into different families, including the Family Ceratosauridae, the "horned lizards." The Ceratosaurs are characterized by a small horn on their snouts, giving them heavier skulls than other carnosaurs. They lived in North America and East Africa in the Late Jurassic Period (195 to 140 million years ago), roaming fern savannas and wooded flood plains. Scattered teeth and bones found in Tanzania also indicate that it may have lived in Africa as well. (Remember that, at this time, the supercontinent Pangaea was just beginning to break up in the Late Jurassic Period.)

One member of the Family Ceratosauridae is Ceratosaurus, which reached 20 feet (six meters) in length and one ton (1,000 kg) in weight. Ceratosaurus had a heavy skull with powerful jaws and sharp, curved teeth, indicating that it was probably an active predator. Ceratosaurus had a pair of bony ridges above its eyes as well as a low horn on its snout. Paleontologists believe that the horn may have been used for defense, but it is fairly small and not really in a good position to be used in a true fight. It might have been used for sexual display, perhaps with the males engaging in ritualistic head-butting battles to determine their position in the social hierarchy among a group of Ceratosauruses.

Trackways found in the Morrison Formation in western North America are believed to belong to Ceratosaurus. These trackways suggest that Ceratosaurus may have travelled in groups and may have hunted in packs the way that many mammalian predators do. Unfortunately, skeletons of Ceratosaurus are rare and are not found preserved in groups, which may indicate that they were solitary hunters.

Unlike other carnosaurs, Ceratosaurus had four well-developed digits ("fingers") on its manus ("hand"). Members of the Family Megalosauridae, such as Dilophosaurus, and the Family Allosauridae, which included Allosaurus, had only three digits in their manus. Members of the Family Tyrannosauridae, which included Albertosaurus, Alioramus, Daspletosaurus, Tarbosaurus and Tyrannosaurus, only had two digits on their manus.

Another unusual characteristic seen in Ceratosaurs is a narrow row of small bony plates running down its back and tail, giving the appearance of a serrated crest. It has been suggested that these plates might have been used to control body temperature in the same way as the plates seen in Stegosaurus and the "sail" in Dimetrodon. To me, these plates seem to be too small to be used for any significant temperature regulation and may have perhaps been used in sexual display.

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