2010年1月15日 · A mong living tetrapods, a dichotomy in locomotor styles was long accepted. Birds and mammals, two different and highly derived amniote lineages, have an erect stance and a parasagittal gait (with the exception of some monotremes), whereas the more basal non-avian reptiles and amphibians sprawl their limbs and move them more laterally.

Because Euparkeria, Silesaurus and Marasuchus are used as outgroups, one could reasonably argue that the positive correlation between them and basal members of dinosaurian lineages is an artefact of character coding. It is possible that if more characters relevant to non-dinosaurs were included, taxon correlation would have found negative ...