Menefeeceratops

MEANING: Menefee Formation horned face

PERIOD: Late Cretaceous

CONTINENT: North America

Menefeeceratops is one of the earliest and most basal known members of the ceratopsids, and the oldest known centrosaurine. It was approximately 4 m long, and had two large horns above the eyes like many other ceratopsids. Its age and location were instrumental in helping to understand the evolution and diversification of the centrosaurine dinosaurs.

Menefeeceratops is from the Late Cretaceous. The Cretaceous is the third and final geological period of the Mesozoic Era, with the Late Cretaceous making up roughly the second half of it, lasting from about 100 to 66 million years ago. It was a time of significant evolutionary change, with dinosaurs reaching their greatest diversity before the mass extinction at the end of the Cretaceous.

The Cretaceous was a period with a relatively warm climate, though the Late Cretaceous experienced a global cooling trend, caused by falling levels of carbon dioxide in the atmosphere. The continents were nearing their present positions, but high sea levels flooded low-lying regions, turning Europe into an archipelago, and forming the Western Interior Seaway in North America. These seas were home to a variety of marine reptiles, including mosasaurs and plesiosaurs, while pterosaurs and birds shared the skies.

On land, dinosaurs continued to thrive and diversify during the Late Cretaceous, producing many of the most well-known groups, including tyrannosaurs, hadrosaurs, and pachycephalosaurs. Established Cretaceous dinosaur clades like the ceratopsians, ankylosaurs, and dromaeosaurs continued to flourish. Sauropod species consisted almost exclusively of titanosaurs, which seemed to be confined to the Southern Hemisphere for much of the Late Cretaceous. Flowering plants and grasses diversified and spread, becoming the dominant flora similar to what we see today.

The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene (K–Pg) extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. This event, likely triggered by an asteroid impact, is marked by the abrupt K–Pg boundary, a distinct geologic layer separating the Mesozoic and Cenozoic Eras. In its aftermath, mammals and avian dinosaurs rapidly diversified, becoming the dominant land animals of the Cenozoic Era.

Menefeeceratops is a ceratopsian. Ceratopsia is a group of herbivorous, beaked dinosaurs that thrived in what are now North America, Europe, and Asia. They primarily flourished during the Cretaceous Period, although ancestral forms lived earlier, in the Late Jurassic. Ceratopsians lived until the Cretaceous–Paleogene extinction event, 66 million years ago, when they went extinct along with the other non-avian dinosaurs.

Early members of the ceratopsian group were small bipedal animals. Later members became very large quadrupeds and developed elaborate facial horns and frills extending over the neck. While these frills might have served to protect the vulnerable neck from predators, they may also have been used for display or thermoregulation. Ceratopsians ranged in size from 1 meter and 23 kilograms to over 9 meters and 9,100 kilograms.

Ceratopsians are easily recognized by features of the skull. Though less pronounced in basal ceratopsians, more derived species, like the ceratopsids are characterized by beaks, rows of shearing teeth in the back of the jaw, elaborate nasal horns, and a shelf that extends back and up into a frill. Various shapes and arrangements of well-developed brow horns and elaborate spines on the frill are also characteristic of many species.