The putative lissamphibian stem-group: phylogeny and evolution of the dissorophoid temnospondyls

Abstract

Dissorophoid temnospondyls are widely considered to have given rise to some or all modern amphibians (Lissamphibia), but their ingroup relationships still bear major unresolved questions. An inclusive phylogenetic analysis of dissorophoids gives new insights into the large-scale topology of relationships. Based on a TNT 1.5 analysis (33 taxa, 108 characters), the enigmatic taxonPerryellais found to nest just outside Dissorophoidea (phylogenetic defintion), but shares a range of synapomorphies with this clade. The dissorophoids proper are found to encompass a first dichotomy between the largely paedomorphic Micromelerpetidae and all other taxa (Xerodromes). Within the latter, there is a basal dichotomy between the large, heavily ossified Olsoniformes (Dissorophidae + Trematopidae) and the small salamander-like Amphibamiformes (new taxon), which include four clades: (1) Micropholidae (Tersomius,Pasawioops,Micropholis); (2) Amphibamidae sensu stricto (Doleserpeton,Amphibamus); (3) Branchiosauridae (Branchiosaurus,Apateon,Leptorophus,Schoenfelderpeton); and (4) Lissamphibia. The generaPlatyrhinopsandEoscopusare here found to nest at the base of Amphibamiformes. Represented by their basal-most stem-taxa (Triadobatrachus,Karaurus,Eocaecilia), lissamphibians nest withGerobatrachusrather than Amphibamidae, as repeatedly found by former analyses.UUID:http://zoobank.org/dadf36db-e003-4af7-bfa7-44d79bc04450

Histological skeletochronology indicates developmental plasticity in the early Permian stem lissamphibian Doleserpeton annectens

“…In particular, it is well-represented by long bones, more specifically femora (Figure 1). Therefore, the abundance of material, in concert with the highly nested position of D. annectens within Amphibamiformes (e.g., Schoch, 2019;Sigurdsen & Bolt, 2010), makes this taxon an ideal candidate for exploring aspects of developmental paleobiology along the presumed lissamphibian stem. The objectives of this study are twofold:…”

“…Doleserpeton annectens Bolt, is an early Permian amphibamiform, a clade of small‐bodied dissorophoid temnospondyls that has been frequently hypothesized to be closely related to some (e.g., Anderson, Reisz, Scott, Fröbisch, & Sumida, ; Pardo, Small, & Huttenlocker, ) or all (e.g., Bolt, ; Schoch, ; Sigurdsen & Bolt, ) of the lissamphibian crown groups (but see Marjanović & Laurin, , for an advocacy of a monophyletic origin within the lepospondyls). Doleserpeton annectens is known only from the karst deposits near Richards Spur, Oklahoma, where it occurs as part of the diverse tetrapod assemblage interpreted to represent an upland ecosystem (MacDougall, Tabor, Woodhead, Daoust, & Reisz, ).…”

“…In particular, it is well‐represented by long bones, more specifically femora (Figure ). Therefore, the abundance of material, in concert with the highly nested position of D. annectens within Amphibamiformes (e.g., Schoch, ; Sigurdsen & Bolt, ), makes this taxon an ideal candidate for exploring aspects of developmental paleobiology along the presumed lissamphibian stem. The objectives of this study are twofold: (a) to compile and to examine the skeletochronology of D. annectens using long bone histology and (b) to assess the effect of sample size on skeletochronological studies through the use of sensitivity analyses by subsampling the exceptionally large sample size ( n = 60) available for this taxon.…”

Dissorophid diversity at the early Permian cave system near Richards Spur, Oklahoma, USA

“…As a result of the differing depositional environments, the Richards Spur locality captures an exceptionally diverse community of terrestrial tetrapods (>40 recognized species), including a number of endemic taxa and many small-bodied taxa that would normally be lost to hydrodynamic sorting in highenergy fluvial systems (MacDougall et al, 2017). Part of this assemblage is a diverse array of terrestrial dissorophoid temnospondyls, a clade that has long been of interest as putative stem lissamphibians (e.g., Bolt, 1969;Sigurdsen and Bolt, 2010;Sigurdsen and Green, 2011;Schoch, 2019) or as stem batrachians (e.g., Anderson et al, 2008b;. Among the Richards Spur dissorophoids are members of the Dissorophidae, a medium-sized clade with distinctive osteoderm morphotypes that is extensively documented from the Permo-Carboniferous of North America.…”

A Juvenile Specimen of the Trematopid Acheloma From Richards Spur, Oklahoma and Challenges of Trematopid Ontogeny

“…Trematopids are a Permo-Carboniferous clade of dissorophoid temnospondyls that are well-documented from North American and European regions of the supercontinent Pangea. Together with the armored dissorophids, the trematopids form Olsoniformes, a clade of medium-large, terrestrial dissorophoids (e.g., Anderson et al, 2008;Schoch, 2018). Trematopids are most readily identified by the presence of an elongate, typically subdivided ("keyhole-shaped") naris, the function of which remains unresolved (e.g., Dilkes, 1993).…”