nomen | Peltophorum dubium | nomen novum | Nomen nescio | Nomen |
In 1999, Paul Penkalski and Peter Dodson concluded that Ceratops, despite being is a nomen dubium because the material is too meager, appeared closely related to Avaceratops which even may be a juvenile Ceratops; there is not enough material to prove it.
Craspedodon lonzeensis, described by Louis Dollo in 1883, is the type species, although it is considered a nomen dubium since it is based on fragmentary material (teeth only).
It was renamed Ponerosteus exogyrarum (species name amended) by George Olshevsky in 2000; however, the taxon is considered a nomen dubium by most, as the type material is extremely poor, being apparently an internal cast of a tibia from an animal that may or may not be a dinosaur.
In his 1990 review, Ralph Molnar noted that the type cannot be distinguished from tail vertebrae from ornithomimids or allosaurids, and considered it to be an indeterminate theropod and a nomen dubium or (more likely) an invalid taxon.
Originally classified by Yang in 1982 in Heterodontosauridae, Dianchungosaurus lufengensis affinities were doubted by some, who regarded it as a nomen dubium, but it was until recently usually considered a valid heterodontosaurid.