Forgotten Dinosaurs: Agathaumas sylvestris
In 1872, Edward Cope named Agathaumas sylverstris, based on a pelvis and a number of vertebrae discovered in southwest Wyoming. It was technically the first ceratopsian dinosaur to be named and described, but without a skull, Cope had little idea of what the animal looked like.
The discovery of Triceratops and Monoclonius (=Centrosaurus) fossils would provide a better idea of what sort of animal Agathaumas was. Still, it remains unclear how journalist William Ballou came up with this published description:
“Its ponderous horned skull suggests the appearance of a rhinoceros, and its high, curved back and bulk an elephant. In front was a knife-like beak, on the nose a stout horn, and on the top of the head a pair of large pointed horns, and on the back of the head a row of sharp projections.”
Although not based on any particular fossil evidence, the Ballou description was presumably the basis for Charles Knight's Agathaumas painting (above), which depicts the dinosaur as a sort of spiny uber-Triceratops. Knight’s painting was in turn copied exactly for the Agathaumas that appeared in the 1925 film "The Lost World".
Today, all fossils referred to Agathaumas are thought to be Triceratops, and the name-bearing holotype is a non-diagnostic nomen dubium.