Ankalagon

Ankalagon is an extinct genus of large carnivorous mammal in the family Mesonychidae, a group of hoofed predators, that lived in North America during the Paleocene epoch. Its only known species, Ankalagon saurognathus, comes from the Nacimiento Formation of New Mexico and is known from the latest Torrejonian. It is the largest mesonychid known from the Paleocene of North America, with a skull as large as that of a brown bear, though its body was probably small relative to the skull. The name honors Ancalagon, the great dragon of Tolkien's The Silmarillion, and the species name means lizard jaw. Leigh Van Valen first proposed the genus as Ancalagon in 1978, found the name was already used by a Cambrian priapulid worm, and renamed it Ankalagon in 1980. Differences in jaw and canine size between two specimens with similar molars give the best evidence of sexual dimorphism among mesonychids. Its close relationship to Dissacus navajovius leaves open whether it is a distinct genus or a species of Dissacus.