Ceratosaurus

Phylogeny: Dinosauria > Saurischia > Theropoda > Neotheropoda > Ceratosauria > Neoceratosauria > Ceratosauridae

Overview: In 1883, a fossil hunter in the employ of the renowned Othniel C. Marsh discovered the fossilized remains of a decently large theropod. Recovered bones included the skull, much of the neck, spine and tail vertebrae, the shoulder, pelvis, and some limb bones. These remains were sent back east to Marsh, who quickly determined it was a new taxon. In the following year, the genus Ceratosaurus was established. Its name, meaning “horned lizard”, referred to the prominent horn on the animal’s snout, as well as to ridges above the eyes. It would be more accurate to refer to these as crests, as most recent studies have determined they were probably too fragile to be used for anything other than display. The nasal “horn” was tall and blade-like, while the eye ridges were more subtle. In life, keratin probably encases them, increasing their size and possibly bearing some bright colors to catch the eye of a potential mate, or to intimidate rivals. Ceratosaurus acts as the namesake of the clade Ceratosauria, which was an early branching lineage of neotheropods that would later give rise to the abelisaurids like Carnotaurus and Majungasaurus.

Scientists have since described a few other Ceratosaurus specimens. In addition to Marsh’s original type species, C. nasicornis, two other species were later described, but these specimens most likely just represent different growth stages. Ceratosaurus was around six to seven meters long, so it was a medium to large-sized theropod. The legs were short, but strong, while its arms were fairly small, though not to the extent of some later ceratosaurs. Its hands bore four digits, a somewhat “primitive” trait, though the fourth digit was very small. Within the jaws were some notably long, blade-like teeth. Genyodectes from South America, a possible close ceratosaurid relative, also had enormous teeth for its size. Ceratosaurus is known to have lived alongside a couple of other large-bodied theropods, namely Torvosaurus and Allosaurus. All three probably occupied different niches as predators. The long-legged Allosaurus may’ve hunted in open terrain, while Ceratosaurus stalked forested areas. Ceratosaurus is known from the Morrison Formation in the United States, as well as Portugal’s Lourinhã Formation. Potential prey may’ve included Dryosaurus, Camptosaurus and Stegosaurus.