Late Triassic Tetrapod Tracks of Western North America

Significant tetrapod footprint assemblages from the Late Triassic of western North America include the following ichnotaxa: Gwyneddichnium majore Bock, 1952, Rhynchosauroides ispp. Maidwell, 1911, Brachychirotherium parvum (Hitchcock, 1889) Brachychirotherium thuringiacum Rühle von Lilienstern, 1938, Apatopus lineatus Baird, 1957, Grallator cursorius Hitchcock, 1858, Anchisauripus sillimani Hitchcock, 1843, Eubrontes isp. Hitchcock, 1845, Eosauropus cimarronensis Lockley et al., 2006a, Evazoum sirigui Nicosia and Loi, 2003, Barrancapus cresapi Hunt et al., 1993a, Atreipus milfordensis (Bock, 1952), Pentasauropus isp. Ellenberger, 1970, Brasilichnium elusivum Leonardi, 1981 and Ameghinichnus isp. Casamiquela, 1964. Most tracksites are from the youngest (Apachean = late Norian-Rhaetian) portion of the Chinle and Glen Canyon groups. Track sites occur in Wyoming, Utah, Colorado, Arizona, New Mexico and Oklahoma. There are four named ichnocoenoses present in the Late Triassic of western North America: Evazoum, Brachychirotherium (Brontopodus ichnofacies), Grallator (Grallator ichnofacies), and Brasilichnium (Chelichnus ichnofacies). In addition, the Characichnos ichnofacies is present. There are two superposed ichnofaunas in the Chinle/Glen Canyon – the upper ichnofauna can be distinguished by the presence of sauropodomorph (and other) tracks.