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Late Triassic dinosaurs from the western United States

A review of all the Late Triassic dinosaurs from the western USA.

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Abstract

Western North America has one of the most extensive fossil records of Late Triassic dinosaurs. All Upper Triassic strata are assigned to the Chinle Group which yields four successive, dinosaur-bearing faunas. Otischalkian (early Tuvalian) dinosaur specimens are fragmentary and indeterminate. Adamanian (late Tuvalian) dinosaurs include a herrerasaurid, Camposaurus arizonensis nov. gen. et sp., Caseosaurus crosbyensis nov. gen. et sp., Tecovasaurus murryi, a new ornithischian and an indeterminate prosauropod. Revueltian (early-middle Norian) dinosaurs include Chindesaurus bryansmalli, two new herrerasaurids, a prosauropod, Revueltosaurus callenderi, Technosaurus smalli, Lucianosaurus wildi, Protoavis texensis and the original syntypes of Coelophysis bauri, Apachean (Rhaetian) evidence for dinosaurs is principally ichnological (Grallator, Pseudotetrasauropus Tetrasauropus), btu at least three dinosaurs are known from osseous remains, including the neotype of Coelophysis bauri. Dinosaurs define three biogeographic provinces in the Late Triassic. In North America, dinosaurs are rare before the late Tuvalian (late Carnian) and appear to become increasingly numerous through the remainder of the Late Triassic.