New insights into vertebrate assemblages from the lower Chañares Formation (Ladinian−earliest Carnian, Ischigualasto−Villa Unión Basin), northwest Argentina

DESOJO, J. B.; EZCURRA, M.D.; FIORELLI, L.E.; MARTINELLI, A. G.; VON BACZKO, M.B.; TABORDA, J.R.A.; HECHENLEITNER, E.M.; EZPELETA, M.; TROTTEYN, M.J; GOUIRIC-CAVALLI, S.

Opole

Congreso; XIII ANNUAL MEETING; 2015

EUROPEAN ASSOCIATION OF VERTEBRATE PALAEONTOLOGISTS

wline">The Triassic witnessed the origin or early evolutionary radiation of multipleamniote clades, such as lepidosauromorphs, rhynchosaurs, archosaurs, turtles andmammaliaforms. The major diversification of these lineages started during the MiddleTriassic and the continental outcrops of the Chañares Formation (northwest Argentina)are among the best that document this event worldwide. Recent fieldworks in thelowermost levels of the Chañares Formation at the type and three new localities (Brazodel Puma, El Torcido and Campo Córdoba) yielded unknown vertebrate groups andconsiderably improved the knowledge of other clades from this unit. We report for thefirst time the presence of lobe-finned fishes (Sarcopterygii, Actinistia), beingrepresented by a fragment of skull roof. Among amniotes, several nonhyperodapedontine rhynchosaurid, doswelliid archosauriform and dicynodont partialskeletons were collected within the first five metres of the formation. The absence ofproterochampsids and dinosauromorphs in the first 5 metres of the Chañares Formationsuggests a different faunal association to that previously known from the upper levels ofthe lower member of the unit (e.g., the Chañares type locality). The study of thelowermost levels of the Chañares Formation bridges a crucial gap between the wellknown early Middle Triassic assemblages of southern Pangaea (e.g., the Manda beds ofTanzania and the Yerrapalli Formation of India) and the younger type Chañares faunaand the Dinodontosaurus Assemblage Zone of southern Brazil. This morecomprehensive knowledge of the faunal associations of Pangaea will shed light on theflourishing of archosaurs during the Late Triassic and subsequently later in theMesozoic.