Palaeoecology and palaeoenvironment of Discosauriscus Kuhn, 1933 with exceptional preservation of skin and intestine molds from the early Permian of Franchesse (Allier, France)

The Carboniferous-Permian is a key period concerning the emergence and diversification of major tetrapod clades such as amphibians and amniotes. This is particularly the case of the Seymouriamorpha Watson, 1917. Some seymouriamorphs are well-known, such as Seymouria Broili, 1904 from North America and Germany, but the ecology of most taxa remains debated. This is the case of Discosauriscus Kuhn, 1933 from the early Permian of Europe. Here we provide a preliminary study of new specimens from the early Permian Lagerstätte of Franchesse (Allier, France) whose exceptionally well-preserved soft tissues including skin and intestinal casts provide valuable insights into the palaeoecology of Discosauriscus. We describe for the first time the complete skin external and histological features of a seymouriamorph indicating that juvenile discosauriscids already displayed epidermal scalation. This suggests a skin adapted towards terrestrial lifestyle in juvenile Discosauriscus. The recovery of an in situ cololite facilitates the identification of seymouriamorph coprolites found ex situ, and thus, future interpretations of the specific diet of this taxon. In order to better understand how these soft tissues have been preserved, we also conducted a taphonomic study including a stratigraphic and palaeoenvironmental analysis of the fossil layer deposits. Our results suggest that pronounced volcanic activity at work during the early Cisuralian of the Bourbon-l’Archambault Basin may be the cause of the multiple Permian mass mortality assemblages found at Franchesse, as well as the exceptional preservation of the fossil remains from this site.