A new proterochampsid Chanaresuchus ischigualastensis (Diapsida, Archosauriformes) in the Early Late Triassic Ischigualasto Formation, Argentina

TROTTEYN, MARÍA JIMENA; MARTÍNEZ, RAICARDO N.; ALCOBER, OSCAR

JOURNAL OF VERTEBRATE PALEONTOLOGY

SOC VERTEBRATE PALEONTOLOGY

Año: 2012 vol. 32 p. 485 - 489

0272-4634

The proterochampsids are a group of crocodile-like archosauriforms usually considered as one of the potential successive sister-taxa of the crown-group Archosauria (e.g., Sereno and Arcucci, 1990; Sereno, 1991; Dilkes and Sues, 2009; Ezcurra et al., 2010). The clade is currently endemic for the late Middle to the early Late Triassic of South America. The best known proterochampsids come from the Chañares and Ischigualasto formations, which belong to the Ischigualasto-Villa Unión Basin (Fig. 1), formed during the breakup of Gondwana (Uliana and Biddle, 1988; Ramos and Kay, 1991). The tetrapod assemblage from the Chañares Formation (Anisian-early Carnian; Desojo et al., 2011) has been usually interpreted to differ from that of the Ischigualasto Formation (late Carnian-earliest Norian; Martínez et al., 2011), and this traditional view also applies for proterochampsids. In the Chañares Formation the proterochampsid genera Chanaresuchus, Gualosuchus, and Tropidosuchus (Romer, 1971, 1972; Arcucci, 1990) were documented, whereas in the Ischigualasto Formation only the genus Proterochampsa was reported (Reig, 1959). The latter highlighted a complete replacement at a generic level among these proterochampsid assemblages in southwestern Pangea. However, an almost complete proterochampsid skeleton from the Late Triassic Ischigualasto Formation is preliminarily described here and assigned to the traditional Middle Triassic genus Chanaresuchus (cf. Sill et al., 1994). Accordingly, the new proterochampsid record reported here changes the pattern of macroevolutionary history of the group during the Middle to Late Triassic southwestern in Pangea.