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

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.

The phylogenetics of Teleosauroidea (Crocodylomorpha, Thalattosuchia) and implications for their ecology and evolution

“…The above analyses, similar to recent studies (Ősi et al, 2018;Foffa et al, 2019;Sachs et al, 2019a), find many aspects of the phylogeny to be consistent, including:…”

“…See Johnson, Young & Brusatte (2020) for more detail.Remarks-initially, the type species of the genus Steneosaurus (MNHN.RJN 134), Steneosaurus rostromajor Geoffroy Saint-Hilaire, 1825, was composed of a rostrum (MNHN.RJN 134c-d) and orbital region (MNHN.RJN 134a-b); however, the orbital section comes from a metriorhynchid. The validity of this taxon has been called into question due to its fragmentary nature (Eudes-Deslongchamps, 1867) and paraphyletic or polyphyletic nature of Steneosaurus in phylogenetic studies(Mueller-Töwe, 2006;Ősi et al, 2018;Foffa et al, 2019;. Currently, only one taxon can hypothetically be referable to S. rostromajor, Neosteneosaurus; however, due to lack of autapomorphic features, uncertainty of teleosauroid ontogenetic and sexual dimorphic stages, a generic concept that has changed multiple times, and poor preservation, S. rostromajor is currently regarded as a nomen dubium(Johnson, Young & Brusatte, 2020).Andrianavoay gen. nov.Type species-Steneosaurus baroni Newton, 1893.…”

Peer Review #3 of "Revision of the Late Jurassic deep-water teleosauroid crocodylomorph Teleosaurus megarhinus Hulke, 1871 and evidence of pelagic adaptations in Teleosauroidea (v0.1)"

“…The overall picture of crocodylomorph interrelationships are similar to those found in previous iterations of this merged dataset (Ristevski et al, 2018;Ősi et al, 2018). Thalattosuchia Manuscript to be reviewed S' (including 'S.'…”

Inner ear sensory system changes as extinct crocodylomorphs transitioned from land to water

“…3 and 4), are optimized on the phylogeny to predict ancestral states for the major clades, demonstrating a trend of increasing PC1 scores (increasingly pelagicshaped ears) in thalattosuchians. Key cranial and postcranial features related to aquatic lifestyles are listed next to the nodes at which they appeared, based on optimizations (43). This demonstrates that thalattosuchians first developed features permitting aquatic locomotion before they developed a modified pelagic labyrinth morphology.…”

“…Phylogenetic Comparative Methods. For the following phylogenetic methods, we utilized a consensus phylogeny of Crocodylomorpha based on the latest iteration of the Crocodylomorph SuperMatrix Project (43)(44)(45). The relationships of the species in our dataset are generally well resolved, but a few taxa are labile in recent phylogenetic analyses.…”