Concavenator

Concavenator is an extinct genus of carcharodontosaurid theropod dinosaur that lived approximately 130 million years ago during the Early Cretaceous period (Barremian age). The type species is C. corcovatus. Concavenator corcovatus means "Cuenca hunter with a hump". The fossil was discovered in the Las Hoyas fossil site of Spain by paleontologists José Luis Sanz, Francisco Ortega, and Fernando Escaso from the Autonomous University of Madrid and the National University of Distance Education. Concavenator was a medium-sized primitive carcharodontosaurid, reaching long and . It possessed several unique features, including the two extremely tall vertebrae in front of the hips that formed a tall, narrow, pointed crest (possibly supporting a hump) on the dinosaur's back. The function of such crests, however, is currently unknown. Paleontologist Roger Benson from the University of Cambridge speculated that one possibility is that "it is analogous to head-crests used in visual displays", but the Spanish scientists who discovered it noted it could also be a thermal regulator. Concavenator had structures resembling quill knobs on its ulna, a feature known only in birds and other feathered theropods, such as Velociraptor. Quill knobs are created by ligaments which attach to the feather follicle and, since scales do not form from follicles, the authors ruled out the possibility that they could indicate the presence of long display scales on the arm. Instead, the knobs have been thought to probably anchor simple, hollow, quill-like structures. Such structures are known both in coelurosaurs, such as Dilong, and in some ornithischians, like Tianyulong and Psittacosaurus. If the ornithischian quills are homologous with bird feathers, their presence in Concavenator and other allosauroids would be expected. However, if ornithischian quills are not related to feathers, the presence of these structures in Concavenator would show that feathers had begun to appear in earlier, more primitive forms than coelurosaurs.