Dromaeosauridae, Matthew and Brown 1922
Ornithodesmus cluniculus Seeley, 1887
Six vertebrae, which are all fused. Viewed laterally, the sacrum is slightly arched, with continuous neural blade formed by the neural spines. A platform projects from the bases of the neural spines and links with the diapophyses. There is a shallow sulcus along the ventral surface of the fused sacral vertebrae and the first two vertebrae have pleurocoels, set in deep excavations.
Little bit of history, as this entry’s a bit short. Ornithodesmus was originally described as a bird, was then re-described as a pterosaur, was then discovered to be a dinosaur, was classified as a troodontid (although the material it was compared to eventually turned out to be misidentified itself), then a dromaeosaur. Basically, no-one really knows what it is, although most palaeontologists agree it is a dromaeosaur. Even if it is, it is not the same as the large velociraptorine(s) also known from the Isle of Wight.
NAISH, D., HUTT, S. and MARTILL, D. M. 2001. Saurichian (sic) dinosaurs 2: theropods. In MARTILL, D. M. and NAISH, D (eds). Dinosaurs of the Isle of Wight. The Palaeontological Association. Field Guide to Fossils 10, 242-309.
NAISH, D. 2011. Theropod dinosaurs. In Batten, D. J. (ed.) English Wealden Fossils. The Palaeontological Association (London), pp. 526-559.