Basing a description off of the limited material of the type specimen is difficult. It can be done however, and comparison of the spikes, vertebrae, and general outlay of the type specimen's slab offered a lot of clues to Mantell in 1833. Recognizing a reptilian body from that little amount of material is quite impressive as is. Considering that much of the anatomy of this dinosaur is still unknown, and that the holotype replacing the type fossil does not constitute much more than the original fossil did, the descriptions and assignment of Hylaeosaurus based on what is available is thanks to solid scientific inquiry, description, and the process of review. As mentioned yesterday, the review process has changed the systematic position of Hylaeosaurus a little, but overall the description of Mantell stating that this reptilian fossil was from a quadrupedal animal that was rather large and armored was fairly accurate. Of course, Mantell was working with a much more complete animal than had been discovered for Iguanodon or Megalosaurus at the time, and that certainly allowed him to be more detailed in his description. I may have mislabeled the holotype as the type in the past few days when I shared a picture of it. Highlighting some of the details in better detail as a drawing, enjoy the view of this 1868 pen and ink illustration of the holotype R3775 housed at NMH London.