The integument of pelagic crocodylomorphs (Thalattosuchia: Metriorhynchidae)

Abstract

Metriorhynchidae are the only archosaurs that show adaptations to a highly pelagic lifestyle. This morphology is paralleled by ichthyosaurs and plesiosaurs, which share a streamlined, largely scaleless skin surface. Although published metriorhynchid material indicates a similar condition, no detailed description of their integument has been carried out. New data from several specimens representing at least three genera are shown here, revealing a uniform skin type lacking any traces of scales or scutes and instead showing folded and transverse fibers. A hypocercal tail fluke comparable to that of ichthyosaurs is present in metrorhynchids. Surface anomalies on metriorhynchid skin are interpreted as potential epizootic scars, similar to those from barnacles, or bite marks. A broad comparison implies deep homologies with plesiosaur and ichthyosaur skin. We also describe skin details of early (teleosauroid) thalattosuchians for the first time. Unlike Metriorhynchidae, their integument is demonstrated to be very similar to that of extant crocodylians, which can be partially explained by their inferred onshore behavior. There is generally a high threshold for extensive skin modifications in aquatic reptiles.

Tough to digest: first record of Teleosauroidea (Thalattosuchia) in a regurgitalite from the Upper Jurassic of north‐eastern Italy

“…2019; Spindler et al . 2021), associated with increased adaptation to a pelagic environment. Bathysuchus megarhinus and Aeolodon priscus (together with Mycterosuchus nasutus and Sericodon jugleri ) were found to be phylogenetically close by Johnson et al .…”

A new specimen of Solnhofia parsonsi from the Upper Jurassic (Kimmeridgian) Plattenkalk deposits of Painten (Bavaria, Germany) and comments on the relationship between limb taphonomy and habitat ecology in fossil turtles

“…Among the latter, fishes are by far the most common group, being represented by actinopterygians, chondrichthyans, and coelacanths [ 7 ]. Fossil reptiles are comparatively abundant and include rhynchocephalians, ichthyosaurs, turtles, the thalattosuchians Cricosaurus albersdoerferi and Dakosaurus sp., atoposaurid neosuchians, Pterodactylus antiquus and other pterosaurs, and the theropod dinosaur Sciurumimus albersdoerferi [ 7 – 11 , 26 , 27 ]. Most of these specimens, however, have not been described in detail yet and several probably represent new taxa.…”

The geologically oldest specimen of Pterodactylus: a new exquisitely preserved skeleton from the Upper Jurassic (Kimmeridgian) Plattenkalk deposits of Painten (Bavaria, Germany)

“…Among the latter, fishes are by far the most common group being represented by actinopterygians, chondrichthyans, and coelacanths (Albersdörfer and Häckel 2015). Fossil reptiles are abundant compared to other quarries and include rhynchocephalians, ichthyosaurs, turtles, the thalattosuchians Cricosaurus albersdoerferi and Dakosaurus sp., atoposaurid neosuchians, pterosaurs and the theropod dinosaur Sciurumimus albersdoerferi (Rauhut et al 2012;Tischlinger and Frey 2013;Albersdörfer and Häckel 2015;Spindler and Albersdörfer 2019;Sachs et al 2021;Spindler et al 2021), though it must be noted that most specimens have not been described in detail yet and thus several may represent new taxa. In general, the fossils from the Rygol Quarry are extremely well preserved and relatively abundant, especially those of terrestrial vertebrates.…”