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[dinosaur] Tanystropheus (Triassic archosauromorph) lifestyle likely more terrestrial based on taphonomy




Ben Creisler
bcreisler@gmail.com



A new paper:



Susan R. Beard & Heinz Furrer (2017)
Land or water: using taphonomic models to determine the lifestyle of the Triassic protorosaur Tanystropheus (Diapsida, Archosauromorpha).
Palaeobiodiversity and Palaeoenvironments (advance online publication)
DOI: https://doi.org/10.1007/s12549-017-0299-7
https://link.springer.com/article/10.1007/s12549-017-0299-7


The Middle Triassic protorosaur Tanystropheus has been considered as both a terrestrial and aquatic taxon based on several lines of biomechanical and distributional evidence, but determining conclusively which habitat was most likely has remained problematic. Specimens of Tanystropheus longobardicus from the Middle Triassic Besano Formation, Monte San Giorgio, are used to investigate the possibility that palaeoecology can be inferred from skeletal taphonomy, which is compared to that of the pachypleurosaurid Serpianosaurus mirigiolensis (considered to be entirely aquatic) and the protorosaur Macrocnemus bassanii (terrestrial) from the same formation. The preservation of Tanystropheus was found to be more similar to Macrocnemus than Serpianosaurus implying carcasses of Tanystropheus originated in terrestrial or at least marginal and near-shore, shallow marine settings. That these were also the most probable habitats in life is supported by the relatively lower number of Tanystropheus (and also Macrocnemus) compared to Serpianosaurus. The study has further implications for the integument of the taxon, which remained sufficiently coherent to prevent the loss of disarticulated elements during an interval of floating necessary to reach the Monte San Giorgio Basin where carcasses came to finally rest. Loss of skeletal completeness was subsequent to arrival at the seabed and as a result of weak bottom current activity that also affected Serpianosaurus.