The largest specimen of<i>Apateon</i>and the life history pathway of neoteny in the Paleozoic temnospondyl family Branchiosauridae

Fröbisch, Nadia B.; Schoch, Rainer R.

doi:10.1002/mmng.200800012

Cited by 28 publications

(5 citation statements)

References 45 publications

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“…Branchiosaurids are often found in high-elevation lake deposits of the Variscian orogen, which have been interpreted to be more seasonally disparate (e.g., Clausing and Boy, 2000). Lakes would have offered a relatively stable environment compared to lowland fluvial systems that would have produced strong selection pressures for alternative life strategies such as neoteny (e.g., Fröbisch and Schoch, 2009b; Sanchez et al, 2010). Conversely, dissorophoids in lowland environments (e.g., the Texas red beds) would not have experienced the same physiological constraints of pronounced elevation and thus radiated in terrestrial settings.…”

Section: Discussionmentioning

confidence: 99%

The amphibamiformNanobamus macrorhinusfrom the early Permian of Texas

Gee

Reisz

2019

J. Paleontol.

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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.

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Section: Discussionmentioning

confidence: 99%

The amphibamiformNanobamus macrorhinusfrom the early Permian of Texas

Gee

Reisz

2019

J. Paleontol.

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“…Apateon , Leptorophus , Schoenfelderpeton (Boy, 1972, 1986, 1987; Werneburg, 1991, 2007a; Schoch & Fröbisch, 2006; Schoch & Milner, 2008; Fröbisch & Schoch, 2009b)…”

Section: Methodsmentioning

confidence: 99%

Phylogeny of Paleozoic limbed vertebrates reassessed through revision and expansion of the largest published relevant data matrix

Marjanović

Laurin

2019

PeerJ

126

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The largest published phylogenetic analysis of early limbed vertebrates (Ruta M, Coates MI. 2007. Journal of Systematic Palaeontology 5:69–122) recovered, for example, Seymouriamorpha, Diadectomorpha and (in some trees) Caudata as paraphyletic and found the “temnospondyl hypothesis” on the origin of Lissamphibia (TH) to be more parsimonious than the “lepospondyl hypothesis” (LH)—though only, as we show, by one step. We report 4,200 misscored cells, over half of them due to typographic and similar accidental errors. Further, some characters were duplicated; some had only one described state; for one, most taxa were scored after presumed relatives. Even potentially continuous characters were unordered, the effects of ontogeny were not sufficiently taken into account, and data published after 2001 were mostly excluded. After these issues are improved—we document and justify all changes to the matrix—but no characters are added, we find (Analysis R1) much longer trees with, for example, monophyletic Caudata, Diadectomorpha and (in some trees) Seymouriamorpha; Ichthyostega either crownward or rootward of Acanthostega; and Anthracosauria either crownward or rootward of Temnospondyli. The LH is nine steps shorter than the TH (R2; constrained) and 12 steps shorter than the “polyphyly hypothesis” (PH—R3; constrained). Brachydectes (Lysorophia) is not found next to Lissamphibia; instead, a large clade that includes the adelogyrinids, urocordylid “nectrideans” and aïstopods occupies that position. As expected from the taxon/character ratio, most bootstrap values are low. Adding 56 terminal taxa to the original 102 increases the resolution (and decreases most bootstrap values). The added taxa range in completeness from complete articulated skeletons to an incomplete lower jaw. Even though the lissamphibian-like temnospondyls Gerobatrachus, Micropholis and Tungussogyrinus and the extremely peramorphic salamander Chelotriton are added, the difference between LH (R4; unconstrained) and TH (R5) rises to 10 steps, that between LH and PH (R6) to 15; the TH also requires several more regains of lost bones than the LH. Casineria, in which we tentatively identify a postbranchial lamina, emerges rather far from amniote origins in a gephyrostegid-chroniosuchian grade. Bayesian inference (Analysis EB, settings as in R4) mostly agrees with R4. High posterior probabilities are found for Lissamphibia (1.00) and the LH (0.92); however, many branches remain weakly supported, and most are short, as expected from the small character sample. We discuss phylogeny, approaches to coding, methods of phylogenetics (Bayesian inference vs. equally weighted vs. reweighted parsimony), some character complexes (e.g. preaxial/postaxial polarity in limb development), and prospects for further improvement of this matrix. Even in its revised state, the matrix cannot provide a robust assessment of the phylogeny of early limbed vertebrates. Sufficient improvement will be laborious—but not difficult.

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“…The fossil record shows that Micromelerpteon had alternative life-history strategies as known from modern salamanders including neotenic adults that retained an aquatic lifestyle and larval somatic features, as well as metamorphosed individuals [34,43]. However, a marked metamorphosis with a strong condensation of events comparable to that of lissamphibians likely only evolved within dissorophoid amphibians, while in most Palaeozoic temnospondyl the ontogenetic trajectory was much more homogeneous [44][45][46]. It is therefore difficult to identify a clear point in the ontogenetic trajectory at which the larval period ended, despite the excellent fossil record of Micromelerpteon.…”

Section: (A) Abnormal Limb Regenerationmentioning

confidence: 99%

Early evolution of limb regeneration in tetrapods: evidence from a 300-million-year-old amphibian

2014

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Salamanders are the only tetrapods capable of fully regenerating their limbs throughout their entire lives. Much data on the underlying molecular mechanisms of limb regeneration have been gathered in recent years allowing for new comparative studies between salamanders and other tetrapods that lack this unique regenerative potential. By contrast, the evolution of animal regeneration just recently shifted back into focus, despite being highly relevant for research designs aiming to unravel the factors allowing for limb regeneration. We show that the 300-million-year-old temnospondyl amphibian Micromelerpeton, a distant relative of modern amphibians, was already capable of regenerating its limbs. A number of exceptionally well-preserved specimens from fossil deposits show a unique pattern and combination of abnormalities in their limbs that is distinctive of irregular regenerative activity in modern salamanders and does not occur as variants of normal limb development. This demonstrates that the capacity to regenerate limbs is not a derived feature of modern salamanders, but may be an ancient feature of non-amniote tetrapods and possibly even shared by all bony fish. The finding provides a new framework for understanding the evolution of regenerative capacity of paired appendages in vertebrates in the search for conserved versus derived molecular mechanisms of limb regeneration.

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The largest specimen ofApateonand the life history pathway of neoteny in the Paleozoic temnospondyl family Branchiosauridae

Cited by 28 publications

References 45 publications

The amphibamiformNanobamus macrorhinusfrom the early Permian of Texas

The amphibamiformNanobamus macrorhinusfrom the early Permian of Texas

Phylogeny of Paleozoic limbed vertebrates reassessed through revision and expansion of the largest published relevant data matrix

Early evolution of limb regeneration in tetrapods: evidence from a 300-million-year-old amphibian

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