A review of Triassic tetrapod track assemblages from Argentina: a reassessment

MELCHOR, R. N. Y DE VALAIS, S

PALAEONTOLOGY

Año: 2006 vol. 42 p. 355 - 379

0031-0239

This paper contains the first comprehensive ichnotaxonomical review on the Triassic tetrapod track record from Argentina, including previous accounts and new material recently discovered, and an analysis of its composition and stratigraphic distribution. Triassic footprints have been recorded from three basins: the Ischigualasto-Villa Unión and Cuyo basins (north-west Argentina), and the Los Menucos depocenter (northern Patagonia). Most of them come from successions of Middle Triassic age, a lower number from the Late Triassic, and two records from Early Triassic rocks. The known track types include: Brachychirotherium isp., cf. Brachychirotherium isp., Chirotherium barthii, Dicynodontipus ispp., Grallator isp., Rhynchosauroides isp., Rigalitesischigualastianus, Rigalites isp., Tetrasauropus isp., bird-like footprints, chirotheriid footprints and unidentified tridactyl footprints. The ichnogenera Gallegosichnus Casamiquela, 1964, Calibarichnus Casamiquela, 1964, Palaciosichnus Casamiquela, 1964 and Stipanicichnus Casamiquela, 1975 are considered synonyms of Dicynodontipus (Hornstein, 1876). In addition, it is suggested the abandonment of the following ichnogenera (and single ichnospecies) that are based on poorly preserved material: Ingenierichnus sierrai Casamiquela, 1964, Rogerbaletichnus aguilerai Casamiquela, 1964, and Shimmelia chirotheroides Casamiquela, 1964. At least eight Triassic ichnofaunas can be recognized. The most peculiar is that of the Late Triassic Los Menucos depocenter, which is characterized by the dominance of therapsid footprints (Dicynodontipus ispp.). The track assemblages from the Cuyo Basin display the higher ichnodiversity, with five footprint types.