title: A complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs.
abstract: Characterizing the evolutionary history of early dinosaurs is central to understanding their rise and diversification in the Late Triassic. However, fossils from basal lineages are rare. A new theropod dinosaur from New Mexico is a representative of the early North American diversification. Known from several nearly complete skeletons, it reveals a mosaic of plesiomorphic and derived features that clarify early saurischian dinosaur evolution and provide evidence for the antiquity of novel avian character systems including skeletal pneumaticity. The taxon further reveals latitudinal differences among saurischian assemblages during the Late Triassic, demonstrates that the theropod fauna from the Late Triassic of North America was not endemic, and suggests that intercontinental dispersal was prevalent during this time.
authors.affiliation: Division of Paleontology, American Museum of Natural History, New York, NY 10024, USA. nesbitt@jsg.utexas.edu
authors.forename: Sterling J
authors.initials: SJ
authors.lastname: Nesbitt
authors.forename: Nathan D
authors.initials: ND
authors.lastname: Smith
authors.forename: Randall B
authors.initials: RB
authors.lastname: Irmis
authors.forename: Alan H
authors.initials: AH
authors.lastname: Turner
authors.forename: Alex
authors.initials: A
authors.lastname: Downs
authors.forename: Mark A
authors.initials: MA
authors.lastname: Norell
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001842:Bone and Bones / Q000033:anatomy & histology*; D050281:Bones of Lower Extremity / Q000033:anatomy & histology; D001133:Bones of Upper Extremity / Q000033:anatomy & histology; D025061:Dinosaurs / Q000033:anatomy & histology / Q000145:classification; D005580:Fossils; D009516:New Mexico; D010802:Phylogeny; D012863:Skeleton; D012886:Skull / Q000033:anatomy & histology; D013131:Spine / Q000033:anatomy & histology