Phylogeny of the amphibamiform temnospondyls: the relationship of taxa known by adults, larvae and neotenes

Schoch, Rainer R.

doi:10.1080/14772019.2022.2113831

Cited by 4 publications

(5 citation statements)

References 82 publications

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“…humbergense , Leptorophus tener , Schoenfelderpeton prescheri ). These results are consistent with the findings of Schoch (2022).…”

Section: Resultssupporting

confidence: 93%

“…The question of how and where metamorphosis originated in the ancestors of extant amphibians has recently been approached by studies of growth series in temnospondyls, the putative stem‐group of Lissamphibia (Schoch 2002, 2009; Schoch & Fröbisch 2006; Witzmann & Schoch 2006; Werneburg 2017). Life cycles of most temnospondyls differed radically from those of lissamphibians in the absence of metamorphosis and the retention of an aquatic lifestyle (Boy 1974; Schoch 2009, 2022).…”

Section: Figmentioning

confidence: 99%

“…However, a major problem in comparing branchiosaurids with other taxa has always been their paedomorphic appearance (Boy 1972). Combined with the absence of larval forms in related dissorophoids, this has posed major challenges to cladistic analyses (Schoch & Milner 2008; Schoch 2022). In fact, all branchiosaurid taxa except for one are known from larval forms only, the largest of which probably were neotenes (Boy 1972; Fröbisch & Schoch 2009b).…”

Section: Figmentioning

confidence: 99%

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Adult branchiosaurid temnospondyls: the life cycle of Xerodromeus gracilis

Schoch

Werneburg

2023

Papers in Palaeontology

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The Branchiosauridae form a clade of tiny newt‐like, extinct amphibians of overall larval appearance. Although their status as neotenic (perennibranchiate) forms had long been universally accepted, adult specimens are known from only one taxon that was hitherto referred to as Melanerpeton (Apateon) gracile. Here we study this life cycle in depth, which includes the only well‐documented metamorphosis‐like transformation in an early tetrapod outside Lissamphibia. Based on various newly recognized features, Melanerpeton gracile is attributed to a new genus, Xerodromeus. Xerodromeus gracilis is characterized by a short postorbital skull table, wide supratemporal, quadrate condyles well posterior to the occipital ones, ossified endocranial elements, carpals, coracoid and pelvis as well as wedge‐shaped intercentra and cylindrical pleurocentra, of which the latter are identified for the first time in branchiosaurids. The studied size classes are referred to four phases: (A) integration of jaw and cheek, longer snout; (B) stronger teeth, robust limbs, incipient ossification of exoccipital, coracoid and pelvis, change in dermal ornament; (C) larger gape, wider skull, polygonal ornament; and (D) quadrate, coracoid, carpals and vertebral centra ossified, during which a probably terrestrial adult morph developed. Adult X. gracilis is more massively built than amphibamids, and its non‐pedicellate dentition indicates that it was probably feeding on different prey.

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“…humbergense , Leptorophus tener , Schoenfelderpeton prescheri ). These results are consistent with the findings of Schoch (2022).…”

Section: Resultssupporting

confidence: 93%

Section: Figmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

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Adult branchiosaurid temnospondyls: the life cycle of Xerodromeus gracilis

Schoch

Werneburg

2023

Papers in Palaeontology

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“…ML19; Hartman et al, 2019;and references in both). Conversely, the temnospondyl sample is not quite up to date, lacking the results of Gee (2021), Schoch (2022), Schoch and Werneburg (2023) and Werneburg et al (2020Werneburg et al ( , 2021Werneburg et al ( , 2023Werneburg et al ( , 2024 most prominently, not to mention the continued (from ML19) dearth of stereospondyls, on which see Gee (2022), Kligman et al (2023) and Marjanović et al (2024).…”

Section: Methodsmentioning

confidence: 92%

“…The phylogeny of Dissorophoidea, with a trematopid grade at the base and a persistent association of Micromelerpeton with some or all "branchiosaurids", can be ascribed to the insufficient sample of taxa and especially characters; the same no doubt holds for the unusual (but almost completely resolved) topology of the few sampled stereospondylomorphs. To test temnospondyl phylogeny, it will be necessary to merge the present matrix with several others (Gee, 2021(Gee, , 2022Schoch, 2022;Werneburg et al, 2023Werneburg et al, , 2024. The outgroup problem, however, seems reasonably close to solved given the strong support for the position of Temnospondyli relative to Anthracosauria, Gephyrostegidae and Lissamphibia.…”

Section: Othersmentioning

confidence: 98%

The origin of Amniota in phylogenetic context

Marjanović

2024

Preprint

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The membership, phylogeny and external relationships of Amniota quickly achieved “textbook wisdom” status in the mid-1990s, but were all called into question by phylogenetic analyses in the last few years. However, all these analyses and all their predecessors have either focused on early limbed vertebrates and barely extended into Amniota, or focused on amniotes and included very few non-amniotes as outgroups. Here I take an analysis of the first type, perform corrections and updates, and enlarge its sample of amniotes and amniote-related characters (among other things) in order to test these matters. Despite its very high rates of homoplasy, my matrix supports all “microsaurs” as amphibians, perhaps even less close to Amniota than Seymouriamorpha. For Diadectomorpha its “classical” position on the stem of Pan-Amniota is weakly supported; this stem has, however, greatly expanded to include many supposed amniotes, among others the fish-scaled Brouffia. The recent finding of Petrolacosaurus outside Diapsida, indeed outside Amniota along with Captorhinidae, is—weakly—corroborated despite my quite different taxon and character samples. Caseasauria, normally considered part of Pan-Mammalia, is instead nested among the “parareptiles” within Sauropsida; Varanopidae, similarly traditionally placed among the pan-mammals, instead emerges in three separate sauropsid positions. A period of very small body size around the origin of the amniotic egg is not supported by the optimal trees, but trees that seem compatible with it are nearly optimal. Slightly worse trees allow for aïstopods as limbless anthracosaurs. The generally low support for the trees highlights specific needs for future research. Still, it appears that the recently proposed membership of many traditional “microsaurs” in Amniota can be excluded with reasonable confidence, as can a position of Anthracosauria crownward of Temnospondyli or a temnospondyl origin for any extant amphibians. Coding the temporal bone of “microsaurs” and other taxa as the tabular or the supratemporal has practically no effect.

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The evolution of larvae in temnospondyls and the stepwise origin of amphibian metamorphosis

Schoch,

Witzmann

2024

Biological Reviews

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The question of what the ancient life cycle of tetrapods was like forms a key component in understanding the origin of land vertebrates. The existence of distinct larval forms, as exemplified by many lissamphibians, and their transformation into adults is an important aspect in this field. The temnospondyls, the largest clade of Palaeozoic–Mesozoic non‐amniote tetrapods, covered a wide ecomorphological range from fully aquatic to terrestrial taxa. In various species, rich ontogenetic data have accumulated over the past 130 years, permitting the study of early phases of temnospondyl development. In temnospondyls, eight ontogenetic phases have been identified in which the skeleton formed. In branchiosaurids and the eryopiform Sclerocephalus, large parts of the ossification sequence are now known. Most taxa in which small specimens are preserved had aquatic larvae with external gills that superficially resemble larval salamanders. In the edopoids, dvinosaurs, and eryopiforms, the larvae developed slowly, with incompletely ossified axial and appendicular skeletons, but possessed a fast‐developing dermal skull with strong teeth. Irrespective of adult terrestriality or a fully aquatic life, there was no drastic transformation during later ontogeny, but a slow and steady acquisition of adult features. In dissorophoids, the limbs developed at a much faster pace, whereas skull formation was slowed down, especially in the amphibamiforms, and culminating in the neotenic Branchiosauridae. In the zatracheid Acanthostomatops, slow but profound transformation led to a fully terrestrial adult. The basal dissorophoid Stegops retained rapid development of dermal skull bones and established a fully dentigerous, strongly ossified palate early. In Micromelerpeton, formation of the last skull bones was slightly delayed and metamorphosis remained a long and steady phase of morphological transformations. In amphibamiforms, metamorphosis became more drastic, with an increasing number of events packed into a short phase of ontogeny. This is exemplified by Apateon, Platyrhinops, and Amphibamus in which this condensation was maximised. We distinguish three different types of metamorphosis (morphological, ecological and drastic) that evolved cumulatively in early tetrapods and within temnospondyls.

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Phylogeny of the amphibamiform temnospondyls: the relationship of taxa known by adults, larvae and neotenes

Cited by 4 publications

References 82 publications

Adult branchiosaurid temnospondyls: the life cycle of Xerodromeus gracilis

Adult branchiosaurid temnospondyls: the life cycle of Xerodromeus gracilis

The origin of Amniota in phylogenetic context

The evolution of larvae in temnospondyls and the stepwise origin of amphibian metamorphosis

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