Editing Archaeopteryx (section)

=== Growth ===
[[File:Archaeopteryx growth curve.jpg|thumb|upright=1.75|Growth trends compared with other dinosaurs and birds]]

An [[histological]] study by Erickson, Norell, Zhongue, and others in 2009 estimated that ''Archaeopteryx'' grew relatively slowly compared to modern birds, presumably because the outermost portions of ''Archaeopteryx'' bones appear poorly vascularized;<ref name=Erickson_etal_2009/> 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{{nbsp}}micrometres per day) or as fast as that in an ostrich (4.2{{nbsp}}micrometres per day). Using this range of bone growth rates, they calculated how long it would take to "grow" each specimen of ''Archaeopteryx'' to the observed size; it may have taken at least 970 days (there were 375 days in a Late Jurassic year) to reach an adult size of {{cvt|0.8–1|kg}}. The study also found that the avialans ''[[Jeholornis]]'' and ''[[Sapeornis]]'' grew relatively slowly, as did the dromaeosaurid ''[[Mahakala (dinosaur)|Mahakala]]''. The avialans ''[[Confuciusornis]]'' and ''[[Ichthyornis]]'' grew relatively quickly, following a growth trend similar to that of modern birds.<ref>''EurekAlert!'' (8 October 2009), [http://www.eurekalert.org/pub_releases/2009-10/amon-wn100809.php "''Archaeopteryx'' was not very bird-like"].</ref> One of the few modern birds that exhibit slow growth is the flightless [[Kiwi (bird)|kiwi]], and the authors speculated that ''Archaeopteryx'' and the kiwi had similar [[basal metabolic rate]].<ref name=Erickson_etal_2009/>