Ceratosaurus nasicornis was a 20-foot theropod dinosaur which lived in western North America during the late Jurassic Period, about 155-145 million years ago. It is one of the more famous Jurassic meat-eating dinosaurs, along with Allosaurus and Ornitholestes. It is the second-most-common theropod found within the Morrison Formation.
There are several anatomical features which make this animal distinct. Firstly, and most obviously, it has a small flat horn shaped like half of a dinner plate on the end of its nose, as well as a pair of horns over the eyes. These features are almost certainly visual in nature and were not designed for combat. Many paleo-artists, notably Gregory Paul, like to show the horn as being very large and triangular. I might be wrong, but I instead decided to portray the horn as it appears on the skull – low and rounded, not tall and pointy.
This animal also has a single row of scutes or osteoderms – small knobs of bone – running down the middle of its back, extending from the back of the head all the way to the tip of the tail. Many examples of paleo-art show Ceratosaurus with multiple rows of osteoderms, similar in appearance to the South American abelisaurid theropod Carnotaurus (which technically didn’t have osteoderms, per se, since the bumps arranged along Carnotaurus‘ back didn’t have a bony core), but this is not true – Ceratosaurus just had one row of these bony bumps.
Ceratosaurus had unusually large teeth in its upper jaw in proportion to the rest of its head. This is a clue that this particular animal engaged in what is called “hatchet-style” biting and feeding, where the animal opens its jaws as wide as it possibly can, and then forcibly slams its head downward on its prey like a guillotine.
It possessed four fingers on each hand, which indicates that it was of a much more primitive stock than contemporary theropods, which were more advanced and had only three fingers on each hand. Its primitiveness also means that Ceratosaurus was probably less intelligent than other theropods. Granted, big bad Al was no genius either.
Finally, its tail was unusually wide, and some have suggested that because of this, Ceratosaurus might have been a good swimmer.
This drawing was made with a combination of Crayola and Prismacolor colored pencils. No.2 pencil was used for shading.