A new large-bodied thalattosuchian crocodyliform from the Lower Jurassic (Toarcian) of Hungary, with further evidence of the mosaic acquisition of marine adaptations in Metriorhynchoidea

Attila Ősi; Mark T Young; András Galácz; Márton Rabi

doi:10.7717/peerj.4668

A new large-bodied thalattosuchian crocodyliform from the Lower Jurassic (Toarcian) of Hungary, with further evidence of the mosaic acquisition of marine adaptations in Metriorhynchoidea

PeerJ. 2018 May 10:6:e4668. doi: 10.7717/peerj.4668. eCollection 2018.

Authors

Attila Ősi^{1

2}, Mark T Young³, András Galácz¹, Márton Rabi^{4

5}

Affiliations

¹ Department of Paleontology, Eötvös University, Budapest, Hungary.
² Department of Paleontology and Geology, Hungarian Natural History Museum, Budapest, Hungary.
³ Grant Institute, School of Geosciences, University of Edinburgh, Edinburgh, UK.
⁴ Central Natural Science Collections, Martin-Luther Universität Halle-Wittenberg, Halle, Germany.
⁵ Institute for Geosciences, University of Tübingen, Tübingen, Germany.

Abstract

Based on associated and three-dimensionally preserved cranial and postcranial remains, a new thalattosuchian crocodyliform, Magyarosuchus fitosi gen. et sp. nov. from the Lower Jurassic (Upper Toarcian) Kisgerecse Marl Formation, Gerecse Mountains, Hungary is described here. Phylogenetic analyses using three different datasets indicate that M. fitosi is the sister taxon of Pelagosaurus typus forming together the basal-most sub-clade of Metriorhynchoidea. With an estimated body length of 4.67-4.83 m M. fitosi is the largest known non-metriorhynchid metriorhynchoid. Besides expanding Early Jurassic thalattosuchian diversity, the new specimen is of great importance since, unlike most contemporaneous estuarine, lagoonal or coastal thalattosuchians, it comes from an 'ammonitico rosso' type pelagic deposit of the Mediterranean region of the Tethys. A distal caudal vertebra having an unusually elongate and dorsally projected neural spine implies the presence of at least a rudimentary hypocercal tail fin and a slight ventral displacement of the distal caudal vertebral column in this basal metriorhynchoid. The combination of retaining heavy dorsal and ventral armors and having a slight hypocercal tail is unique, further highlighting the mosaic manner of marine adaptations in Metriorhynchoidea.

Keywords: Crocodyliformes; Hungary; Marine adaptation; Metriorhynchoidea; Toarcian.

Grants and funding

This work was supported by the National Research, Development and Innovation Office, Hungary (OTKA K 116665) and Eötvös University (D11201/17). This project has received funding from the European Union’s Seventh Framework programme for research and innovation under the Marie Skłodowska-Curie grant agreement No. 609402–2020 researchers: Train to Move (T2M) to Márton Rabi. Márton Rabi is supported by a Volkswagen Foundation grant ‘Research in Museums.’ Mark T. Young received support for his collection visits to Paris (FR-TAF-4021), Stuttgart (DE-TAF-5132), Berlin (DE-TAF-5698) and Budapest (HU-TAF-6505) from the SYNTHESYS project http://www.synthesys.info/, which is financed by the European Community Research Infrastructure Action under the FP7 ‘Capacities’ programme. Mark T. Young is also supported by a Leverhulme Trust Research Project grant (RPG-2017-167), and the University of Edinburgh lab group is supported by a Royal Society Research Grant (RG130018). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.