A new species of Sclerocephalus with a fully ossified endocranium gives insight into braincase evolution in temnospondyls

Abstract

The late Paleozoic temnospondyl Sclerocephalus formed an aquatic top predator in various central European lakes of the late Carboniferous and early Permian. Despite hundreds of specimens spanning a wide range of sizes, knowledge of the endocranium (braincase and palatoquadrate) remained very insufficient in Sclerocephalus and other stereospondylomorphs because even large skulls had unossified endocrania. A new specimen from a stratigraphically ancient deposit at St. Wendel in southwestern Germany is recognized as representing a new taxon, S. concordiae new species, and reveals a completely ossified endocranium. The sphenethmoid was completely ossified from the basisphenoid to the anterior ethmoid region, co-ossified with the parasphenoid, and the basipterygoid joint was fully established. The pterygoid bears a slender, S-shaped epipterygoid, which formed a robust pillar lateral to the braincase. The massive stapes was firmly sutured to the parasphenoid. In the temnospondyl endocranium, character evolution involved various changes in the epipterygoid region, which evolved distinct morphologies in each of the major clades. UUID: http://zoobank.org/5e6d2078-eacf-4467-84cf-a12efcae7c0b

Descriptive anatomy and three-dimensional reconstruction of the skull of the tetrapod Eoherpeton watsoni Panchen, 1975 from the Carboniferous of Scotland

“…An incipient pterygoid flange extending into the subtemporal fossa is also present in some temnospondyls, including Balanerpeton (Milner & Sequeira 1993) and members of Edopoidea (Sequeira 2003), Dissorophoidea (Milner 2018) and Archegosauroidea (Schoch & Sobral 2021). The homology between the flange found in temnospondyls and on the lineage leading to amniotes is uncertain, although recent studies have reconstructed the anterior portion of the medial adductor mandibulae internus (homologous to medial pterygoideus; also see below) in temnospondyls as originating on the interpterygoid vacuities, rather than the pterygoid flange as in amniotes (Witzmann & Werneberg 2017).…”

The disadvantage of derivation: conserved systematic flaws in primary data have repeatedly biased the phylogenetic inference of Temnospondyli (Tetrapoda, Amphibia)

“…The phylogeny of temnospondyls and its various subclades has been frequently examined using computer-assisted methods (e.g., Eltink et al, 2017, 2019; Fernández-Coll et al, 2017; Marsicano et al, 2017, 2021; Marzola et al, 2017; Pacheco et al, 2017; Pardo et al, 2017; Chakravorti and Sengupta, 2018; Gee et al, 2018, 2021; Liu, 2018; Schoch, 2018a, 2018b, 2018c, 2019, 2021a, 2021b; Schoch and Witzmann, 2018; Atkins et al, 2019; Buffa et al, 2019; Schoch and Voigt, 2019; Dilkes, 2020; Gee, 2020b, 2021; Maisch, 2020; Schoch et al, 2020a; Werneburg et al, 2020; Schoch and Milner, 2021; Schoch and Sobral, 2021; Arbez et al, 2022; Schoch & Sues, 2022; Werneburg et al, 2022). The large body of work underscores the import of phylogenetic analyses as the means of inferring evolutionary narratives and informing taxonomic frameworks.…”