Archaeopteryx of "Archaeopteryx" bones appear poorly vascularized; in living vertebrates, poorly vascularized bone is correlated with slow growth rate. They also assume that all known skeletons of "Archaeopteryx" come from juvenile specimens. Because the bones of "Archaeopteryx" could not be histologically sectioned in a formal skeletochronological (growth ring) analysis, Erickson and colleagues used bone vascularity (porosity) to estimate bone growth rate. They assumed that poorly vascularized bone grows at similar rates in all birds and in "Archaeopteryx". The poorly vascularized bone of "Archaeopteryx" might have grown as slowly as that in a mallard (2.5 micrometres per day) or as fast as
Specimens of Archaeopteryx the feather. "Archaeopteryx lithographica" was initially named for this original feather, rather than the full skeleton that was found around the same time, and the feather was originally the formal type specimen and holotype for the species. There are obvious problems with this idea, such as the fact that the feather may have come from a juvenile, or possibly another species altogether. The distal obtuse angle at the tip is not a feature found on the feathers of any other "Archaeopteryx" skeleton with integument imprints. It is possible, however, that the strange angle of the tip is an artifact caused