african broad-mouthed collagen endangered flat-mouthed gray grazer grey heavy herbivore herbivorous hide horns keratin large lattice structured mammal megafauna odd-toed ungulate perissodactyl placid powerful rhino rhinoceros skin snout southern white rhinoceros square-lipped rhinoceros strong thick threatened tough wide-lipped rhinoceros creases folds white rhinoceros African-dwarf-crocodile animal armoured-skin black-crocodile bony-crocodile broad-snouted broad-snouted-crocodile carnivore carnivorous cold-blooded crocodile Crocodilia dense-rainforest distinctive dwarf-crocodile habitat-loss nocturnal open-mouthed osteolaemus-tetraspis reptile reptilian rough-backed-crocodile small solitary-animal vulnerable West-African zoo wrinkled wrinkles cow eating food junior lattice-structured mother odd-toed-ungulate offspring southern-white-rhinoceros