The revision of baphetids from the Middle Pennsylvanian of the Czech Republic: Morphology, ontogeny, palaeoecology, and the reassessment of the phylogeny of Baphetoidea.

Abstract

The baphetoids represent a clade of the Carboniferous stem-tetrapods (Middle Mississippian-Middle Pennsylvanian) with a characteristic extension of the orbits into antorbital vacuities, which formed keyhole-shaped openings on the skull. The more derived baphetids were crocodile-like piscivores frequently occurring in coal-bearing lacustrine deposits with abundant fish fauna and known from Central and Western Europe, the United States, and Canada. Several important specimens referred to the group have historically been reported from the late Carboniferous (Moscovian) of the Czech Republic, but the thorough revision and comparison of this material have never been fully undertaken. Here we provide a morphological revision of all available baphetid material from the late Carboniferous of the Czech Republic, including one newly described specimen. The part of the presumably lost type material of Loxomma bohemicum was rediscovered and shown here to represent a poorly preserved lower jaw fragment of the temnospondyl Capetus palustris, while all remaining material can be referred to Baphetes orientalis and provides an important insight into the poorly known baphetid ontogeny. The species can be characterized by the postorbital with a very thin and sharply pointed postfrontal process and a slightly elongate rectangular lateral process of the bone. Other characteristics formerly used to diagnose this species are most likely ontogenetically influenced. The results of the most comprehensive phylogenetic analysis of the Baphetoidea to date indicate that Baphetinae might be polyphyletic, while "Loxomma" lintonensis has been recovered outside the clade Loxommatinae and cannot be confidently assigned to the Loxomma genus on morphological grounds.