Megacerops

Megacerops (lit.'great horned face') is an extinctgenus of horned brontothere that lived in North America during the Late Eocene, in the Chadronian land mammal age. Megacerops is among the best represented large mammals in the fossil record, known from hundreds of complete skulls and several complete skeletons. As the classic brontothere, Megacerops has enjoyed enduring fame in popular culture, often under various historically used names, such as Brontotherium, Brontops, and Titanotherium.

Megacerops was superficially similar to modern rhinoceroses, but closer to elephants in size. The largest known Megacerops may have been over 2.5 meters (8 ft 2 in) tall at the shoulder and could have weighed up to four or five tonnes. They were among the largest mammals in the Eocene, rivaled only by other brontotheres, and were by far the largest animals in their environment. Adult Megacerops were likely too large to be preyed upon by any contemporary predator.

The horns of Megacerops, its signature feature, were anatomically similar to the ossicones of modern giraffes and are believed to have been used in intraspecific combat. In some cases, Megacerops fossils have been found in mass death assemblages, which suggests that they were social animals that may have traveled herds. Paleoclimatological models of the Eocene and isotope analyses of Megacerops teeth suggest that they lived in warm temperate to subtropical forests and woodlands, and preferred moist environments.

Skulls of Megacerops are highly variable in some features, especially the size and shape of the horns. This was once interpreted as indicating different species and even genera, and has made the taxonomic history of Megacerops highly complex; over fifty species of Chadronian brontotheres have been named historically. The taxonomy is not entirely resolved. Today, variations among the fossils are interpreted largely as the result of sexual dimorphism and other individual variation. The genus contains at least one diagnosable species, the type speciesM. coloradensis. A rarer second species is also generally recognized, M. kuwagatarhinus, distinguished from M. coloradensis by its bifurcating horns.