10 metres (33 ft)
Titanosauria Bonaparte and Coria, 1993
‘Pleurocoelus valdensis‘ Lydekker, 1889
A long-necked sauropod dinosaur, Ornithopsis was a browser, eating tough vegetation with its chisel-like teeth. It was probably only a visitor when it died, as there was insufficient vegetation to support a sauropod population.
The only definitely identified specimen is a single tooth, from the Wealden group, the exact locality being unknown, but the south west coast is probably the best place to look. This is a difficult dinosaur to diagnose, as there is no actual holotype, as the tooth was described as one of a selection of teeth. They reveal enough to designate them to the titanosauriformes, with laterally placed labial grooves. The teeth are very similar to Oplosaurus, except they are less spatulate, and some experts consider that Oplosaurus and Pleurocoelus are differently aged individuals of the same species. It is also likely that Pleurocoelus is actually Astrodon, a very similar animal found elsewhere in the world, which is regarded as a senior synonym, but until a skull is found, this is unprovable.
Material is rare, so please report it if you find some…
NAISH, D. and MARTILL, D. M. 2001d. Saurischian dinosaurs 1: sauropods. In MARTILL, D. M. and NAISH, D (eds). Dinosaurs of the Isle of Wight. The Palaeontological Association. Field Guide to Fossils 10. 185-.241.