Diceratus by Moondawg

Diceratus (meaning "two-horned") is a ceratopsid herbivorous dinosaur genus from the Late Cretaceous period of North America. It is known only from a single poorly preserved skull discovered in Wyoming and described in 1905 as Diceratops.

For many years, it had been considered a species within the genus Triceratops, but recent analysis (Forster, 1996) suggests it is a distinct genus. Since the Diceratops name was preoccupied, it was renamed to Diceratus in 2008.

Diceratus was first described as Diceratops ("two horned face"), but it was found that the name was already in use for a hymenopteran (Foerster, 1868). It was given its current name by Octávio Mateus in 2008.

The paper that described Diceratus was originally part of O. C. Marsh's magnum opus, his Ceratopsidae monograph. Unfortunately, Marsh died (1899) before the work was completed, and John Bell Hatcher endeavored to complete the Triceratops section. However, he died of typhus in 1904 at the age of 42, leaving the paper still uncompleted. It fell to Richard Swann Lull to complete the monograph in 1905, publishing Hatcher's description of a skull separately and giving it the name Diceratops hatcheri.

Since the Diceratops paper had been written by Hatcher, and Lull had only contributed the name and published the paper after Hatcher's death, Lull was not quite as convinced of the distinctiveness of Diceratops, thinking it primarily pathological. By 1933, Lull had had second thoughts about Diceratops being a distinct genus and he put it in a subgenus of Triceratops: Triceratops (Diceratops), including T. obtusus; largely attributing its differences to being that of an aged individual.