Isolated UK Bathonian theropod teeth Project ID: 000457042 Public

6 Media · 2 Specimens · Creator: Simon Wills · Managed by: Simon Wills

Abstract from: WILLS, S., UNDERWOOD, C.J., and BARRETT, P.M., (2022) Machine learning confirms new records of maniraptoran theropods in Middle Jurassic UK microvertebrate faunas. Papers in Palaeontology Current research suggests that the initial radiation of maniraptoran theropods occurred in the Middle Jurassic, although their fossil record is known almost exclusively from the Cretaceous. However, fossils of Jurassic maniraptorans are scarce, usually consisting solely of isolated teeth, and their identifications are often disputed. Here, we apply different machine learning models, in conjunction with morphological comparisons, to a suite of isolated theropod teeth from Bathonian microvertebrate sites in the UK in order to determine if any of these can be confidently assigned to Maniraptora. We generated three independent models developed on a training dataset with a wide range of theropod taxa and broad geographical and temporal coverage. Classifying the Middle Jurassic teeth in our sample against these models, and undertaking morphological comparisons, indicates the presence of at least three distinct dromaeosaur morphotypes, plus a therizinosaur and troodontid in these assemblages. These new referrals significantly extend the ranges of Therizinosauroidea and Troodontidae by some 27 million years. These results indicate that not only were maniraptorans present in the Middle Jurassic, as predicted by previous phylogenetic analyses, but had already radiated into a diverse fauna that pre-dated the break-up of Pangaea. This study also demonstrates the power of machine learning to provide quantitative assessments of isolated teeth in providing a robust, testable framework for taxonomic identifications, and highlights the importance of assessing and including evidence from microvertebrate sites in faunal and evolutionary analyses.