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Late Triassic Marine Reptiles

2017; Springer Nature; Linguagem: Inglês

10.1007/978-3-319-68009-5_8

2452-1639

Silvio Renesto, Fabio M. Dalla Vecchia,

Evolution and Paleontology Studies

During faunal recovery after the Permo-Triassic mass extinction (PTME), several tetrapod lineages independently evolved adaptations to marine life. Thus reptiles became significant elements of marine environments already at the beginning of the Mesozoic Era. The emergence of a diverse assemblage of marine reptiles in the Triassic marked the development of ecosystem complexity comparable with that of modern oceans. Different lineages (ichthyopterygians, sauropterygians and thalattosaurs) diversified quickly throughout the Middle Triassic and their disparity peaked during the late Anisian-early Carnian interval. Subsequently, both diversity and disparity underwent a substantial decrease during the Late Triassic. The last 'pachypleurosaur' and nothosauroid record is early Carnian in age; non-cyamodontoid placodonts were already extinct before the Carnian. Ichthyosaur diversity decreases from the Carnian to the Norian and reaches its minimum in the Rhaetian. Cyamodontoid placodonts are practically missing in the upper Carnian-middle Norian, to appear again in the upper Norian-Rhaetian with the single genus Psephoderma. The last record of the tanystropheid Tanystropheus is late Norian in age, and the range of the enigmatic Pachystropheus is possibly late Norian to early Rhaetian. Non-plesiosaurian sauropterygians, thalattosaurs, and non-parvipelvian ichthyosaurs were already extinct before the Triassic-Jurassic boundary. Pelagic forms, i.e. parvipelvian ichthyosaurs among ichthyosaurs and plesiosaurs among sauropterygians, which had appeared during the Late Triassic, crossed the Triassic-Jurassic boundary, giving rise to subsequent radiations in the Jurassic. Also, chelonians obviously crossed the boundary, while the earliest Jurassic reported record of phytosaurs needs to be confirmed.