Hylaeosaurus

The first Hylaeosaurus fossils were discovered in the Grinstead Clay, West Sussex. On 20 July 1832, fossil collector Gideon Mantell wrote to Professor Benjamin Silliman that when a gunpowder explosion had demolished a quarry rock face in Tilgate Forest, several of the boulders freed showed the bones of a saurian. A local fossil dealer had assembled the about fifty pieces, described by him as a "great consarn of bites and boanes". Having doubts about the value of the fragments, Mantell had nevertheless purchased the pieces and soon discovered they could be united into a single skeleton, partially articulated. Mantell was delighted with the find because previous specimens of Megalosaurus and…

]] Gideon Mantell originally estimated that Hylaeosaurus was about 7.6 m long, or about half the size of the other two original dinosaurs, Iguanodon and Megalosaurus. At the time, he modelled the animal after a modern lizard. Modern estimates range up to 6 m in length. Gregory S. Paul in 2010 estimated the length at 5 m, the weight at 2 tonne. Some estimates are considerably lower: in 2001 Darren Naish e.a. gave a length of 3-4 m. Many details about the build of Hylaeosaurus are unknown, especially if the material is strictly limited to the holotype. Maidment gave two autapomorphies, unique derived traits: the scapula did not fuse with the coracoid, even when the animal was of a…