Notohypsilophodon

Notohypsilophodon was the first hypsilophodont dinosaur ever found in South America, which made it very special to scientists.12

The only skeleton we have is from a young dinosaur, because its backbone bones were not fully fused together.12

Its arm bone, the humerus, had no deltopectoral crest, a ridge that many other dinosaurs have for muscle attachment.2

Its shin bone, the tibia, had a bulge on the front and inner side, which is a unique feature of this dinosaur.2

The fibula, a bone in the lower leg, suddenly became narrow near the middle of its shaft, another special trait.2

Its ankle bone, the astragalus, had a top surface with two levels, which is different from many other ornithopods.2

The foot claws, called unguals, had flat undersides, which may have helped it walk or dig.2