Mammalian? How come? '-saur' comes from the Greek 'sauros' meaning 'lizard' or 'reptile', and in the generation of portmanteau or compound names the first element is often a descriptor with the last element always being the animal type, particularly in the case of dinosaurs. For example, 'bactrosaurus' comes from 'baktron' (club) and 'sauros', so named because club-shaped spines projected from some of its vertebrae. 'Giganotosaurus' comes from 'gigas' (giant), 'noton' (back) and sauros and was so named because it was huge. As such, 'Rhinosaur' would most likely mean 'lizard that has rhino-like features'.