Terrestrial vertebrates from near the Triassic-Jurassic boundary in Portugal: excavation, geological context, and faunal change

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The mass extinction that occurred close to the Triassic/Jurassic (TJ) boundary (ca. 200 Ma) ranks among the “big five” mass die-offs in Earth history. Faunal change involved the origins of nearly all of the major living tetrapod groups (e.g. mammals, lizards, turtles, crocodilians, and lissamphibians), as well as dinosaurs and pterosaurs. An understanding of the end-Triassic mass extinction is crucial to understanding both Mesozoic vertebrate evolution and the origins of the modern vertebrate fauna. However, our understanding is currently limited by the fact that few geological sequences preserve tetrapod fossils in close association with the TJ boundary. In order to better understand the end-Triassic event on land, the discovery and careful documentation of tetrapod-bearing geological units that span the TJ boundary is urgently required. We propose the first comprehensive study of important TJ boundary sections in southern Portugal (Algarve). These sections are unique in preserving vertebrate bone-beds within a few metres of the basaltic lava flows that mark the TJ boundary. We aim to characterise vertebrate faunal change leading up the extinction, yielding new insights into the dynamics of this event.