title: A Late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs.
abstract: It has generally been thought that the first dinosaurs quickly replaced more archaic Late Triassic faunas, either by outcompeting them or when the more archaic faunas suddenly became extinct. Fossils from the Hayden Quarry, in the Upper Triassic Chinle Formation of New Mexico, and an analysis of other regional Upper Triassic assemblages instead imply that the transition was gradual. Some dinosaur relatives preserved in this Chinle assemblage belong to groups previously known only from the Middle and lowermost Upper Triassic outside North America. Thus, the transition may have extended for 15 to 20 million years and was probably diachronous at different paleolatitudes.
authors.affiliation: Museum of Paleontology and Department of Integrative Biology, University of California, Berkeley, CA 94720-4780, USA. irmis@berkeley.edu
authors.forename: Randall B
authors.initials: RB
authors.lastname: Irmis
authors.forename: Sterling J
authors.initials: SJ
authors.lastname: Nesbitt
authors.forename: Kevin
authors.initials: K
authors.lastname: Padian
authors.forename: Nathan D
authors.initials: ND
authors.lastname: Smith
authors.forename: Alan H
authors.initials: AH
authors.lastname: Turner
authors.forename: Daniel
authors.initials: D
authors.lastname: Woody
authors.forename: Alex
authors.initials: A
authors.lastname: Downs
mesh_terms: D000818:Animals; D025061:Dinosaurs / Q000033:anatomy & histology / Q000145:classification; D005269:Femur / Q000033:anatomy & histology; D005580:Fossils; D009516:New Mexico; D010802:Phylogeny; D013628:Talus / Q000033:anatomy & histology; D013977:Tibia / Q000033:anatomy & histology; D013995:Time; D014070:Tooth / Q000033:anatomy & histology