Nedoceratops (from russian prefix "nedo" meaning "insufficient horned face", in reference to its lack of a nasal horn) is a genus of ceratopsid herbivorous dinosaur from the Late Cretaceous period Lance Formation of North America. It is known only from a single poorly preserved skull discovered in Wyoming. In 2010, a published study concluded that Nedoceratops does not represent a distinct genus, but rather a "young adult" form of Triceratops.
RestorationThe paper that described Nedoceratops 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; Diceratops means "two horned face."
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.
Because the Diceratops name was already in use for a hymenopteran (Foerster, 1868), Andrey Sergeevich Ukrainsky gave the animal its current name Nedoceratops in 2007. Unaware that Ukrainsky had already re-named the animal, Octávio Mateus coined another new name for it in 2008, Diceratus. Diceratus is now considered a junior synonym of Nedoceratops.
The poorly preserved skull known as "USNM 2412" is the only fossil of Nedoceratops. Like Hatcher's other Triceratops skulls, it was found in eastern Wyoming, i.c. in 1891 in Niobrara County near Lightning Creek. Superficially, it resembles that of Triceratops, but on closer examination, it is definitely odd: there is just a rounded stump where the nasal horn should be and the occipital (brow) horns stand almost vertically. Compared to other Triceratops skulls, it is slightly larger than average (2.0 m), but its face is rather short. There also are large holes in the frill, unlike other Triceratops skulls known. Some of these may be pathological, others seem to be genetic.
The type species is Nedoceratops hatcheri. Nedoceratops belonged to the Ceratopsia (the name is Greek for "horned faces", Keratopia), a group of herbivorous dinosaurs with parrot-like beaks which thrived in North America and Asia during the Cretaceous Period, which ended roughly 65 million years ago. All ceratopsians became extinct at the end of this era.
Several authors have suggested that Nedoceratops may be directly ancestral to Triceratops, or perhaps its nearest relative. In 2010, John B. Scannella and John R. Horner published a paper in the Journal of Vertebrate Paleontology claiming that the USNM 2412 skull (i.e., of Nedoceratops) belonged to a "young adult" Triceratops. Evidence for this hypothesis included the shapes of the epoccipital and squamosal bones, and a neck frill (parietal bone) that had "incipient" openings (contrasting with no openings in subadult Triceratops and large openings in adult Triceratops formerly assigned to Torosaurus). The authors were of the opinion that the nasal horn of the USNM 2412 skull could have been lost when the animal was alive or when it became fossilized.