Jurassic terrestrial vertebrates from Chubut Province, Argentina: implications for the differentiation of terrestrial vertebrate faunas during the Jurassic

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The Jurassic is an important time for our understanding of vertebrate evolution, as many important clades originated and/or experienced an important radiation during this period. However, our understanding of the Jurassic evolution of terrestrial vertebrates is almost entirely based on the fossil record of the Northern Hemisphere. The only important fauna from the Late Jurassic of Gondwana is so far that of the Tendaguru Formation of Tanzania, but in the absence of comparable Gondwanan faunas it is currently impossible to formulate well-founded hypotheses about the reasons for possible differences or similarities with Laurasian faunas. Apart from possible vicariance and possibly increasing endemism due to the beginning breakup of the supercontinent Pangea, an extinction event towards the end of the Early Jurassic has recently come into focus, which seems to have had a profound impact on at least some clades of terrestrial vertebrates. In the first funding period of the present project, we explored the Upper Jurassic Cañadón Calcáreo Formation in Chubut Province, Argentina, for vertebrate fossils. Numerous new vertebrate remains could be located and at least partially be excavated. Among the new finds are the first pterosaur remains from this formation and the first abelisaurid theropod and stegosaur remains from the Late Jurassic of South America. A new specimen of the small theropod dinosaur Pandoravenator shows this taxon to represent the oldest coelurosaur known from Gondwana, and a new sauropod taxon, which is currently still in preparation, promises to give new insights into the taxonomy and systematic position of several problematic sauropods from the Tendaguru Formation. A new theropod is represented by at least three specimens, which together show almost the entire osteology of the new taxon. It shows similarities with the enigmatic Chilesaurus and might thus help to clarify the systematic position of this problematic genus. Finally, more specimens have been found, but not excavated so far, including at least two partially articulated sauropod skeletons. In the second funding period applied for here we want to continue this work. The new finds will be excavated and prepared, and we plan to finish the preparation and scientific study of the new sauropod and the new theropod taxon. A further aim is the termination of an ongoing PhD project on the geology and palaeoenvironments of the Cañadón Calcáreo Formation as well as an evaluation of the potential of some older Jurassic units within the same province to provide evidence on the evolutionary effects of the end-Early Jurassic extinction event.