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
Archaeopteryx be black throughout, with heavier pigmentation in the distal tip. The feather studied was most probably a dorsal covert, which would have partly covered the primary feathers on the wings. The study does not mean that "Archaeopteryx" was entirely black, but suggests that it had some black colouration which included the coverts. Carney pointed out that this is consistent with what we know of modern flight characteristics, in that black melanosomes have structural properties that strengthen feathers for flight. In a 2013 study published in the "Journal of Analytical Atomic Spectrometry", new analyses of "Archaeopteryx"'s feathers revealed that the animal