MEANING: Horn roof
PERIOD: Late Cretaceous
CONTINENT: North America
Stegoceras is a pachycephalosaurid dinosaur that lived in what is now North America during the Late Cretaceous period. It is one of the most completely known pachycephalosaurs, and one of the few known from more than just the skull. Stegoceras was a small, bipedal dinosaur about 2-2.5 m long, and weighed around 10-40 kg. The skull was roughly triangular in shape with a short snout, and had a thick, broad, and relatively smooth dome on the top. Stegoceras had a thick shelf over the back of the skull, and a thick ridge over the eyes. Much of the skull was ornamented by round outgrowths and knobs, many in rows, and the largest formed small horns on the shelf.
Stegoceras is from the Cretaceous. The Cretaceous is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period.
The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct flora and fauna, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth by the end of the Cretaceous, coincident with the decline and extinction of previously widespread gymnosperm groups.
The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary (K–Pg boundary), a geologic signature associated with the mass extinction that lies between the Mesozoic and Cenozoic Eras.
Stegoceras is a pachycephalosaur. Pachycephalosauria, meaning "thick headed lizards" is a group of ornithischian dinosaurs. Along with the ceratopsians, they make up the clade Marginocephalia. They almost all lived during the Late Cretaceous Period, and are exclusive to the Northern Hemisphere. Pachycephalosaurians are bipedal, herbivorous animals with thick skulls. These bony skulls can be domed, flat, or wedge-shaped depending on the species, and were often surrounded by nodes and spikes. There is some debate why pachycephalosaurians had such heavily armored heads, but one leading hypothesis is that they were used in intra-species combat, similar to modern-day goats.