Ornithopsis

Phylogeny: Dinosauria > Saurischia > Sauropodomorpha > Plateosauria > Massopoda > Sauropodiformes > Sauropoda > Gravisauria > Eusauropoda > Neosauropoda > Macronaria > Titanosauriformes

Overview: Ornithopsis has a somewhat confusing history of study, which is to be expected from a dinosaur based on a fossil first described in the early nineteenth century. The bit of bone was first described in the 1830’s by Gideon Mantell, who had earlier described the genus Iguanodon. Mantell would conclude the bone came from the back of the skull, referring it to Iguanodon. Two decades later, another study would affirm Mantell’s conclusion, but the researcher Harry G. Seeley would go on to refute it in the 1870’s. Seeley recognized the fossil as part of a vertebrae, also noting it possessed hollow chambers throughout, similar to those of birds. Described by Seeley in 1870, the generic name of Ornithopsis literally means “birdlike”, in reference to this trait. Seeley thought it was related to birds or pterosaurs, but it was later confirmed to be a sauropod dinosaur. Studies afterward would find it to be a junior synonym of either Bothriospondylus or Chondrosteosaurus.

Chondrosteosaurus and Bothriospondylus were genera described on quite limited fossils, with both being treated as dubious today by most researchers. The genus Ornithopsis, however, seems to be a distinct and valid taxon, its remains having some diagnostic features. Other additional fossils are thought to belong to Ornithopsis, though only one species is usually seen as valid – Ornithopsis hulkei. Most come from England, but fossils in mainland Europe may also belong to it. Modern studies tend to classify Ornithopsis as a macronarian sauropod, probably in the clade Titanosauriformes. It grew to be about fifteen or sixteen meters long, so it was a medium-sized sauropod. The hollow spaces in its vertebrae were filled with a system of air sacs in life, which lightened its weight, but were also linked with its respiratory system, similar to those seen in actual birds. Ornithopsis is known from the Wessex Formation, so it likely had to contend with predators like Neovenator.