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 seizing it with its jaws if it was small enough, or with its claws if it was larger. Over the years, twelve body fossil specimens of "Archaeopteryx" and a feather that may belong to it have been found. All of the fossils come from the limestone deposits, quarried for centuries, near Solnhofen, Germany. The initial discovery, a single feather, was unearthed in 1860 or 1861 and described in 1861 by Hermann von Meyer. It is currently located at the Natural History Museum of Berlin. This is generally assigned to "Archaeopteryx" and was the initial holotype, but whether it is a