title: Fine structure of bone in dinosaurs, birds and mammals.
abstract: After observation of detailed structural evidence for the origin of birds from dinosaurs, and in light of evidence that dinosaur bone tissue resembles the histology in mammals, the histology of bone has become one of the focal points in discussions of the physiology of dinosaurs and Mesozoic birds. Most of this microstructural information has focused on features related to the vascular organization and the amount of remodelled bone around vascular canals. However, the finer structures have received less attention, although differences in such structures have been observed among modern vertebrates. Here we present evidence that canaliculi--the submicrometre-sized channels that interconnect bone cells and vascular canals--and the collagen fibre bundles in bone are differently organized among certain dinosaur lineages. Ornithomimid dinosaurs are more like birds than mammals in these features. In canalicular structure, and to some extent in fibre bundle arrangement, ornithischian dinosaurs are more like mammals. These differences in both canalicular and lamellar structure are probably linked to differences in the process and rate of bone formation.
authors.affiliation: Burke Museum of Natural History and Culture & Department of Geological Sciences, University of Washington, Seattle 98195, USA. rensb@u.washington.edu
authors.forename: J M
authors.initials: JM
authors.lastname: Rensberger
authors.forename: M
authors.initials: M
authors.lastname: Watabe
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001717:Birds; D001842:Bone and Bones / Q000033:anatomy & histology*; D005580:Fossils; D008322:Mammals; D012104:Reptiles