The first fish remains (Sarcopterygii and Actinopterygii) from the late Ladinian−earliest Carnian (Chañares Formation) of Argentina: a wider palaeolatitudinal distribution for early mawsoniid coelacanthiforms?

DESOJO, J.B.; GOUIRIC-CAVALLI, S.; MARTINELLI, A.G.; FIORELLI, L.E.; EZCURRA, M.D.

Opole

Congreso; XIII ANNUAL MEETING; 2015

EUROPEAN ASSOCIATION OF VERTEBRATE PALAEONTOLOGISTS

ine"></The amniote fossil record of the late Ladinian−earliest Carnian ChañaresFormation is among the richest worldwide for the Middle Triassic. However, nonamniote osteichthyan remains were unknown from this highly fossiliferous unit, untilthey were collected during recent fieldwork. A specimen sampled from the lowermember (~7 metres above the base), and probably late Ladinian in age, belongs to afragment of dermal bone assignable to a coelacanthiform mawsoniid (Sarcopterygii,Actinistia) based on its ornamentation. Remains collected from the upper member (4metres below the top; early Carnian) of the unit are represented by patches of scales thatresemble those of some pseudobeaconiid perleidiforms (Actinopterygii). The record ofa putative mawsoniid in the Middle Triassic of South America is of particular interestbecause it represents the first evidence of the group in southern palaeolatitudes duringthe early evolution of the clade. The oldest unambiguous mawsoniids come from theMiddle Triassic of Europe and have subsequently been recorded from North Americaduring the Late Triassic. The specimen described here indicates a widerpalaeolatitudinal distribution for mawsoniids than previously recognised, spanning froma palaeolatitude of 20ºN in the Northern Hemisphere to 45ºS in southwestern Pangaea.This distribution indicates the presence of the group in tropical to temperate/semi-aridpalaeoclimates in the north and south, respectively, and suggests a relatively broadclimatic tolerance for early members of the clade. Accordingly, the probably broadgeographic distribution of early mawsoniids matches the biogeographic historyobserved in multiple Middle Triassic vertebrates.