New Comparative Data on the Long Bone Microstructure of Large Extant and Extinct Flightless Birds

Here, we investigate whether bone microanatomy can be used to infer the locomotion mode (cursorial vs. graviportal) of large terrestrial birds. We also reexamine, or describe for first time, histology several extant and extinct flightless birds (i) document histovariability between skeletal elements hindlimb; (ii) improve our knowledge histological diversity birds; (iii) reassess previous hypotheses pertaining growth strategies modern palaeognaths. Our results show that birds, inferred as graviportal based on hindlimb proportions, have thicker diaphyseal cortices and/or more bony trabeculae in medullary region than cursorial report time occurrence marks (not associated with an outer circumferential layer-OCL) ratites. These observations support earlier flexible patterns present when selection pressures rapid within a single year are absent. OCL skeletally mature high incidence pathologies among species is attributed fact these individuals were probably long-lived zoo specimens.