The impact of metamorphosis on the cranial osteology of giant salamanders of the genus <i>Dicamptodon</i>

Schoch, Rainer R.; Pogoda, Peter; Kupfer, Alexander

doi:10.1111/azo.12318

Cited by 8 publications

(12 citation statements)

References 41 publications

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“…It has a single tooth row located on its anterior process ( Fig. 1 C and D ) as found in neotenic adults of the amphibamiform Apateon caducus ( 44 ), Mesozoic salamanders such as Kokartus , Beiyanerpeton , Qinglongtriton , and Chunerpeton ( 21 , 24 , 28 , 29 ), and larval forms of some modern salamanders ( 47 ). The pterygoid has a shallow trough on its dorsal surface ( Fig.…”

Section: Resultsmentioning

confidence: 92%

Middle Jurassic fossils document an early stage in salamander evolution

Jones

Benson

Skutschas

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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Salamanders are an important group of living amphibians and model organisms for understanding locomotion, development, regeneration, feeding, and toxicity in tetrapods. However, their origin and early radiation remain poorly understood, with early fossil stem-salamanders so far represented by larval or incompletely known taxa. This poor record also limits understanding of the origin of Lissamphibia (i.e., frogs, salamanders, and caecilians). We report fossils from the Middle Jurassic of Scotland representing almost the entire skeleton of the enigmatic stem-salamander Marmorerpeton . We use computed tomography to visualize high-resolution three-dimensional anatomy, describing morphologies that were poorly characterized in early salamanders, including the braincase, scapulocoracoid, and lower jaw. We use these data in the context of a phylogenetic analysis intended to resolve the relationships of early and stem-salamanders, including representation of important outgroups alongside data from high-resolution imaging of extant species. Marmorerpeton is united with Karaurus , Kokartus , and others from the Middle Jurassic–Lower Cretaceous of Asia, providing evidence for an early radiation of robustly built neotenous stem-salamanders. These taxa display morphological specializations similar to the extant cryptobranchid “giant” salamanders. Our analysis also demonstrates stem-group affinities for a larger sample of Jurassic species than previously recognized, highlighting an unappreciated diversity of stem-salamanders and cautioning against the use of single species (e.g., Karaurus) as exemplars for stem-salamander anatomy. These phylogenetic findings, combined with knowledge of the near-complete skeletal anatomy of Mamorerpeton, advance our understanding of evolutionary changes on the salamander stem-lineage and provide important data on early salamanders and the origins of Batrachia and Lissamphibia.

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Section: Resultsmentioning

confidence: 92%

Middle Jurassic fossils document an early stage in salamander evolution

Jones

Benson

Skutschas

et al. 2022

Proc. Natl. Acad. Sci. U.S.A.

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“…In salamandrids, the alae extend laterally during metamorphosis, but fail to surround the internal carotid artery, which instead passes through the occipito‐otic. Schoch et al (2021) noted the position of the foramen for the internal carotid artery varies in size and position within the alae of the parasphenoid of metamorphosed dicamptodontids, and is absent altogether in some paedomorphic specimens. Alae of the basal plate are found in cryptobranchids, including a clear pair of channels that pass through the basal plate to accommodate the internal carotid arteries.…”

Section: Discussionmentioning

confidence: 99%

Salamander braincase morphology as revealed by micro‐computed tomography

Szostakiwskyj

Anderson

2022

Journal of Morphology

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Morphological data sets are misleading in salamander (Caudata) phylogeny due to the relative homoplasy of the dermal skull observed in paedomorphic forms, leading to the trend of excluding morphology when exploring questions of salamander phylogeny. Investigations in caecilians (Gymnophiona) have demonstrated that the inclusion of braincase morphology can rescue morphological phylogenetic analyses and produce topologies congruent with molecular data sets. We scanned 28 species (25 genera) of salamander, representing all 10 families, with high‐resolution micro‐computed tomography to investigate braincase variation. We describe the morphology of the braincase for all 10 families and distinguish between paedomorphic and metamorphic morphologies. Our results demonstrate a general uniformity amongst metamorphic species with variation largely restricted to the occipito‐otic region. A greater range of variation is observed within paedomorphic forms than would be expected when considering the homoplasy of the dermal skull. Obligate paedomorphic forms demonstrate considerably more variation in the anterior braincase than do facultative paedomorphs, which we suggest is evidence of a greater complexity in the evolution and development of these forms than neoteny alone would produce. This raises the question of character independence within morphological data sets and warrants further investigation into the correlation of other characters before morphological data are omitted.

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“…To our knowledge, this is the only known case of a sexually dimorphic presence/absence dental polymorphism in an amphibian. Larval salamanders and caecilians were excluded in our dentition survey but differ in patterns of dentition from adults (Wake 1976, Clemen and Gren 2018), such as the transient presence of teeth on the splenials, palatines, and pterygoids that are lost during development (Schoch et al 2019). Maxillary and premaxillary teeth are synchronized in all anuran taxa that we sampled, but two species in the genus Telmatobius have maxillary teeth in the absence of premaxillary teeth (Barrionuevo 2017).…”

Section: Discussionmentioning

confidence: 99%

Rampant tooth loss across 200 million years of frog evolution

Paluh

Riddell

Early

et al. 2021

Preprint

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Teeth have been broadly maintained across most clades of vertebrates but have been lost completely at least once in actinopterygian fishes and several times in amniotes. Using phenotypic data collected from over 500 genera via micro-computed tomography, we provide the first rigorous assessment of the evolutionary history of dentition across all major lineages of amphibians. We demonstrate that dentition is invariably present in caecilians and salamanders, but teeth have been lost completely more than 20 times in frogs, a much higher occurrence of edentulism than in any other vertebrate group. The repeated loss of teeth in anurans is associated with a specialized diet of small invertebrate prey as well as shortening of the lower jaw, but it is not correlated with a reduction in body size. Frogs provide an unparalleled opportunity for investigating the molecular and developmental mechanisms of convergent tooth loss on a large phylogenetic scale.

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The impact of metamorphosis on the cranial osteology of giant salamanders of the genus Dicamptodon

Cited by 8 publications

References 41 publications

Middle Jurassic fossils document an early stage in salamander evolution

Middle Jurassic fossils document an early stage in salamander evolution

Salamander braincase morphology as revealed by micro‐computed tomography

Rampant tooth loss across 200 million years of frog evolution

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