 Medullary bone has been found in fossils of the theropods "Tyrannosaurus" and "Allosaurus" and of the ornithopod "Tenontosaurus".Because the line of dinosaurs that includes "Allosaurus" and "Tyrannosaurus" diverged from the line that led to "Tenontosaurus" very early in the evolution of dinosaurs, the presence of medullary bone in both groups suggests that dinosaurs in general produced medullary tissue.On the other hand, crocodilians, which are dinosaurs' second closest extant relatives after birds, do not produce medullary bone.