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 a fish. Fragments of the braincase and upper jaw were later identified and published by other researchers. While Owen's 1863 monograph on the specimen is historically considered to be the first real description of "Archaeopteryx", Henry Woodward, assistant of the Geological Department of the British Museum, had published a shorter article on the specimen in December 1862. Here he provided a detailed description as well as the first published illustration of the specimen, sketched from the original. Rather than an attempt to steal Owen's glory, Woodward gave him due credit in this article as its official describer. Woodward's article nevertheless