Named By: Othniel Charles Marsh - 1884.
Classification: Chordata, Reptilia, Dinosauria, Saurischia, Theropoda, Ceratosauria, Ceratosauridae.
Species: C. nasicornis (type), C. dentisulcatus, C. ingens, C. magnicornis, C. meriani, C. stechowi, C. willisobrienorum.
Size: Typically between 6 to 8 meters. Some specimens indicate that it may have been slightly larger.
Known locations: USA, Morrison Formation. Portugal. Tanzania.
Time period: Kimmeridgian to Tithonian of the Jurassic.
Fossil representation: Many specimens representing several species.
has been known to science since towards the end of the nineteenth
century, and thanks to its head ornamentation, has long been one of
the most popular. Early on, Othniel Charles Marsh considered the
blade like nasal horn to have been a weapon against other dinosaurs,
but this is no longer considered likely, especially when you compare
Ceratosaurus to other theropod dinosaurs that had
head crests such as
which are all more likely for a visual
Ceratosaurus also possessed a pair of smaller
above its eyes that were extensions of the lacrimal bones.
The distinctive nasal horn of Ceratosaurus was made from an extension of the nasal bones at the snout of the skull. The horn itself is not a single growth but the fusing of two growths from separate bones. A juvenile specimen also features the beginnings of the horn from these two bones that have not yet fused together, possibly indicating that the nasal horn, when grown, was a sign of reproductive maturity.
Another interesting feature that seems to make Ceratosaurus unique among the theropods was the osteoderms that ran down its back. The purpose for these is not exactly known. Osteoderms are often evolved as a form of defence and if this were the case with Ceratosaurus, then that could suggest that there were other larger predators at the time (possibly those like Saurophaganax) that would not think twice about attacking Ceratosaurus. It may have also been for extra defence in intraspecific combat with rivals.
The tail of Ceratosaurus was quite flexible and supported by high vertebral spines. It has been suggested that if Ceratosaurus ever took to the water, the tail would have been a very powerful swimming aid, used in a similar fashion as a crocodiles.