First record of Metriorhynchidae (Crocodylomorpha, Thalattosuchia) from the Lower Cretaceous of northeastern Italy: high-resolution biostratigraphy, morphological description and comparative pelagic taphonomy

The Italian record of Metriorhynchoidea, a Mesozoic clade of marine crocodylomorphs, is represented by fossils from the Veneto, Lombardy and Sicily regions. A new specimen (FMCR FOS03817) from the Lower Cretaceous of Asiago area (Veneto region, northeastern Italy) is here described for the first time and comparatively studied with a Middle Jurassic specimen (FMCR FOS03839) coming from the same locality. A petrographic and micropalaeontological analysis was performed in order to assess the stratigraphic position of both specimens. The newly described specimen is herein ascribed to the basal Berriasian (Lower Cretaceous) and referred to Metriorhynchidae incertae sedis after a comparative assessment of its morphology with coeval longirostrine crocodylomorphs. A taphonomic and petrographic comparative analysis between FMCR FOS03817 and FMCR FOS03839 is presented to compare their preservational status, being the two specimens coming from similar pelagic settings. While the Cretaceous specimen clearly shows signs of heavy biological alterations by extended bioerosion, the Middle Jurassic fossil appears histologically well preserved, an uncommon feature for a pelagic taphonomic setting. This key difference is here hypothesised to be linked to a faster burial provided by stromatolite-like microbial mats encrustation on the carcass of FMCR FOS03839.