Extreme convergence in the body plans of an early suchian (Archosauria) and ornithomimid dinosaurs (Theropoda).
Living archosaurs comprise birds (dinosaurs) and crocodylians (suchians). The morphological diversity of birds and stem group dinosaurs is tremendous and well-documented. Suchia, the archosaurian group including crocodylians, is generally considered more conservative. Here, we report a new Late Triassic suchian archosaur with unusual, highly specialized features that are convergent with ornithomimid dinosaurs. Several derived features of the skull and postcranial skeleton are identical to conditions in ornithomimids. Such cases of extreme convergence in multiple regions of the skeleton in two distantly related vertebrate taxa are rare. This suggests that these archosaurs show iterative patterns of morphological evolution. It also suggests that this group of suchians occupied the adaptive zone that was occupied by ornithomimosaurs later in the Mesozoic.
Nesbitt
Sterling J
SJ
Division of Paleontology, American Museum of Natural History, Central Park West at 79th Street, New York City, NY 10024, USA. nesbitt@ldeo.columbia.edu
Norell
Mark A
MA
D000222:Adaptation, Physiological; D000489:Alligators and Crocodiles / Q000033:anatomy & histology / Q000145:classification; D000818:Animals; D005075:Biological Evolution; D001717:Birds / Q000033:anatomy & histology / Q000145:classification; D001842:Bone and Bones / Q000033:anatomy & histology*; D025061:Dinosaurs / Q000033:anatomy & histology* / Q000145:classification; D005580:Fossils; D010163:Paleontology; D010802:Phylogeny; D012886:Skull / Q000033:anatomy & histology; D013045:Species Specificity; D013131:Spine / Q000033:anatomy & histology