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

Abstract

Dissorophoids are a diverse clade of predominantly Permo-Carboniferous temnospondyls with a wide geographic distribution and broad ecological diversity. Each of the various dissorophoid clades first appears in the late Carboniferous, but their records are relatively sparse and fragmentary compared to those of the early Permian when dissorophoids reach their peak diversity and distribution, particularly in terrestrial environments where they are by far the most taxonomically diverse clade of non-amniote tetrapods. This provides an impetus for further study of the late Carboniferous terrestrial dissorophoids in order to contextualize the early stages in the clade's radiation into terrestrial ecosystems. Here we present a redescription of the late Carboniferous trematopid Actiobates peabodyi from Kansas, USA, which is represented by a nearly complete skeleton and which represents the earliest occurrence of trematopids in North America. Only the skull was previously described, and the taxon has been largely overlooked in the context of early terrestrial dissorophoid evolution. Here, we provide an updated cranial description, the first postcranial description, and a discussion of the position of A. peabodyi in the context of olsoniform evolution. Our most significant finding is the characterization of postcranial anatomy that is highly similar to that of later trematopid taxa. This high degree of conservatism indicates that the earliest trematopids were already well adapted for terrestrial environments, and post-Carboniferous radiations of olsoniforms may be attributed to an expansion of the dryland terrestrial environments in which these taxa already thrived, rather than to novel acquisition of adaptive features later in the clade's evolution.

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).…”

“…For instance, most taxa (sensu Schoch, 2019) are of early Permian age and reveal a remarkable diversity that suggests a much earlier diversification sometime in the Carboniferous (Schoch and Milner, 2014). Upper Carboniferous deposits in the Czech Republic (Nýřany, Broumov), Germany (Stützerbach in the Thuringian forest), France (Montceau-les-Mines in Sâone et Loire), and the United States (Linton and Five Points in Ohio, Mazon Creek in Illinois, Hamilton Quarry and Garnett in Kansas) have yielded a diverse record of dissorophoid material that documents the presence of most major clades within the group: the micromelerpetids Limnogyrinus elegans Fritsch, 1881 and Nyranerpeton amilneri Werneburg, 2012 (Werneburg, 1994(Werneburg, , 2012Schoch and Witzmann, 2018); the branchiosaurids Branchiosaurus and Apateon (Boy, 1987;Werneburg, 2012); the trematopids Actiobates peabodyi Eaton, 1973, Anconastes vesperus Berman et al, 1987, Fedexia striegeli Berman et al, 2010, Mordex calliprepes Steen, 1938, and Mattauschia laticeps (Fritsch, 1881) (Berman et al, 1987(Berman et al, , 2010Werneburg, 2012;Milner, 2019;Gee and Reisz, 2020a); and the amphibamiforms Platyrhinops lyelli (Wyman, 1858) (Hook and Baird, 1984;Clack and Milner, 2010), Amphibamus grandiceps (Watson, 1940;Milner, 1982), and Eoscopus lockardi Daly, 1994. As recently outlined (Schoch, 2019), major phylogenetic questions remain regarding the Dissorophoidea that range from their early diversification, to the position of branchiosaurids and lissamphibians, to the early evolution of olsoniform and amphibamiform branches (Boy, 1981;Anderson et al, 2008a, b;Schoch, 2012Schoch, , 2013Maddin et al, 2013). It is clear that in addition to applying new preparation techniques to existing material, the discovery of new specimens will play an important role in resolving these uncerta...…”

“…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, andAnderson, 2009 (Reisz et al, 2009;Gee and Reisz, 2018), Eoscopus lockardi (Daly, 1994), Micromelerpetidae (Werneburg, 1991;Boy, 1995;Schoch and Witzmann, 2018), Nanobamus macrorhinus Milner, 2014 (Gee andReisz, 2020b), Pasawioops mayi Reisz, 2008, Platyrhinops lyelli (Clack andMilner, 2010), Scapanops neglectus Schoch and Sues, 2013, and Tersomius texensis Case, 1910(Carroll, 1964Maddin 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.…”

The dissorophoid temnospondyl Parioxys ferricolus from the early Permian (Cisuralian) of Texas

“…In preparing the description, we used the following studies for comparative data: Actiobates peabodyi Eaton, 1973 (Gee and Reisz, 2020), Anakamacops petrolicus Li and Cheng, 1999 (Liu, 2018), Broiliellus texensis Williston, 1914, Cacops spp. (Williston, 1910; Reisz et al, 2009; Gee and Reisz, 2018), Conjunctio multidens Carroll, 1964a (Schoch and Sues, 2013), Dissorophus multicinctus Cope, 1895 (DeMar, 1968; Schoch, 2012), Kamacops acervalis Gubin, 1980 (Schoch, 1999), Mattauschia laticeps Milner, 2019, Palodromeus bairdi Schoch, Henrici, and Hook, 2020, Scapanops neglecta Schoch and Sues, 2013, and Tersomius texensis Case, 1910 (Carroll, 1964a; Maddin et al, 2013).…”

“…Dendrysekos helogenes Steen, 1934 (= Dendrerpeton acadianum Owen, 1853 of many former authors; see discussion in Schoch and Milner, 2014) was used as the outgroup. Scores for the following additional taxa were added: Anakamacops petrolicus (Gee and Reisz, 2020), Kamacops acervalis (Gubin, 1980; Schoch, 1999), Scapanops neglecta (Schoch and Sues, 2013), and Parioxys ferricolus (based on the present study).

Figure 5.Phylogeny of dissorophoid temnospondyls, with particular emphasis on the Dissorophidae and the position of Parioxys ferricolus Cope, 1878.

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