The amphibamiformNanobamus macrorhinusfrom the early Permian of Texas

Abstract

Nanobamus macrorhinus Schoch and Milner, 2014 is a small amphibamiform temnospondyl from the early Permian Arroyo Formation of Texas. It is most readily characterized by an elongate and partially subdivided naris. This condition is superficially reminiscent of that seen in the coeval trematopids, the group to which N. macrorhinus was originally referred to under an interpretation of the holotype as a larval form. This was discounted by later workers, but the amphibamiform affinities of the specimen were not formalized until recently. The specimen has never been described in the context of its amphibamiform affinities and remains poorly characterized, never having been sampled in a phylogenetic analysis. Here we present a complete, updated osteological description of N. macrorhinus, including an improved characterization of its unique mosaic of plesiomorphic and apomorphic features and clarification of the taxon's autapomorphies. Our analysis of the taxon's phylogenetic position within Amphibamiformes shows that N. macrorhinus was recovered as diverging after basal amphibamiforms, e.g., the micropholids, and before derived amphibamiforms, e.g., the amphibamids. This is supported by the unique mixture of retained plesiomorphies, e.g., nonforeshortened postparietals and an oval choana, and apomorphies, e.g., a narrow interorbital region and slender palatal rami of the pterygoid. These results reflect the complexity of terrestrial amphibamiform diversity and provide further insight into the evolutionary history of the lissamphibian stem in terrestrial environments.

A new dissorophoid temnospondyl from the Allegheny Group (late Carboniferous) of Five Points, Mahoning County, Ohio (USA)

“…The non-dissorophoid ingroup taxa are Trimerorhachis (for Dvinosauria), Sclerocephalus (for Eryopiformes), and Acanthostomatops (for Zatracheidae). Five additional taxa were added: Actiobates peabodyi (Gee and Reisz, 2020a), Mattauschia laticeps and Mordex calliprepes (Milner, 2019), Nanobamus macrorhinus (Gee and Reisz, 2020b), and Palodromeus bairdi n. gen. n. sp. Seven new characters were added (14, 16, 28, 42, 60, 63, and 72) to the existing data set, and one character (former 30) was omitted because it overlapped with former character 17 (new number 30) (see Appendix in Supplemental Data for definitions).…”

“…In preparing the description, we referred to the following works for comparative studies: Actiobates peabodyi (Gee and Reisz, 2020a), Amphibamus grandiceps (Milner, 1982), Branchiosauridae (Boy, 1987), Cacops morrisi Reisz, Schoch, and Anderson, 2009 (Reisz et al, 2009; Gee and Reisz, 2018), Eoscopus lockardi (Daly, 1994), Micromelerpetidae (Werneburg, 1991; Boy, 1995; Schoch and Witzmann, 2018), Nanobamus macrorhinus Schoch and Milner, 2014 (Gee and Reisz, 2020b), Pasawioops mayi Fröbisch and Reisz, 2008, Platyrhinops lyelli (Clack and Milner, 2010), Scapanops neglectus Schoch and Sues, 2013, and Tersomius texensis Case, 1910 (Carroll, 1964; Maddin et al, 2013). In addition, we have studied nearly all of the published specimens of dissorophoids first-hand and have assessed a sizeable number of unreported specimens from Linton and Five Points.…”

A redescription of the late Carboniferous trematopid Actiobates peabodyi from Garnett, Kansas

“…Furthermore, the subdivision appears to be a marker of ontogenetic maturity in long‐snouted trematopids (Dilkes, ) such that absence of subdivision is not compelling evidence against trematopid affinities. Narial elongation is found in non‐trematopid dissorophoids (e.g., the amphibamiform Nanobamus macrorhinus and the long‐headed morph of the amphibamiform Micropholis stowi ; Schoch & Rubidge, ; Gee & Reisz, ), but it is never found in dissorophids. Furthermore, the architecture of the trematopid naris is unique, as it markedly truncates the lacrimal, which sends a process of variable length along the ventral narial margin.…”

“…A. peabodyi is often referred to as a trematopid in more recent publications (e.g., Berman, Reisz, & Eberth, ; Berman et al, , ; Berman, Henrici, Martens, Sumida, & Anderson, ; Milner, , 2018), although it is rarely included in phylogenetic analyses (but see, e.g., Polley & Reisz, ) due to the brief original description and the subsequent interpretation of the holotype as a larval individual (Berman et al, ). However, this interpretation was predicated on the description of a “larval” trematopid (UCLA VP 3686) by Olson () that was most recently erected as the holotype of the amphibamiform Nanobamus macrorhinus (Gee & Reisz, ; Schoch & Milner, ). Eaton's only figure also omitted most of the purported features (e.g., hyobranchials) that were used to argue in favor of KUVP 17941 as a larval trematopid.…”

Returning to the roots: resolution, reproducibility, and robusticity in the phylogenetic inference of Dissorophidae (Amphibia: Temnospondyli)

“…‘Amphibamidae’ here refers to the historical concept of what is now Amphibamiformes (in part). Abbreviations: ARM, Atkins, Reisz & Maddin (2019) ; BHBK, Berman et al (2010) ; BHMSA, Berman et al (2011) ; D, Dilkes (2020) ; FR, Fröbisch & Reisz (2008 , 2012 ); FS, Fröbisch & Schoch (2009) ; G, Gee (2020b) ; G* (2021), this study; GBHPH, Gee et al (2021) ; GR, Gee & Reisz (2019) ; HBA, Holmes, Berman & Anderson (2013) ; L, Liu (2018) ; MFEM, Maddin et al (2013) ; PR, Polley & Reisz (2011) ; RB, Ruta & Bolt (2006) ; S, Schoch (2012 , 2018a ); SHH, Schoch, Henrici & Hook (2020) ; SM, Schoch & Milner (2008 , 2021 ); SR, Schoch & Rubidge (2005) ; SS, Schoch & Sues (2013) ; SW, Schoch & Witzmann (2018) .…”