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Temnospondyls of the Triassic. in Mehmood, Singh, Elsler et Benton, 2025. artwork by Mark P. Witton |
Abstract
One of the mysteries of the Permian–Triassic mass extinction was the subsequent success of temnospondyls. Temnospondyls were key early tetrapods in the Carboniferous and Permian and hardly seem to be ideal pioneers in a tough post-extinction world. Did they survive because of some unusual adaptations or by occupying some limited part of the world? We explore temnospondyl success in the Triassic by comparing their functional ecomorphology and palaeogeographic distributions. We find that Early Triassic temnospondyls exhibited all skull sizes and shapes, reflecting a wide diversity of feeding modes: abundant parabolic-snouted forms, and less common longirostrine (long-snouted) and insectivorous (short-skulled) forms. In fact, morphospace occupation by temnospondyls increased dramatically from Late Permian to Early Triassic, and then decreased in the Middle Triassic, but without emphasis on one feeding mode or another. Nor is there any evidence for unusual patterns of evolution: Temnospondyli and subclade Trematosauria follow an Ornstein–Uhlenbeck evolutionary model, suggesting evolution towards a common skull shape. Metoposauroidea, Brachyopoidea and basal Stereospondyli evolved by the stasis model. Further, these Early Triassic temnospondyls did not occupy a limited part of the world; they show temperate distributions, but with some specimens in equatorial regions, contradicting the idea of a permanently impermeable tropical dead zone.
Keywords: geometric morphometrics, ecological function, temnspondyli, Triassic, Permian–Triassic mass extinction
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| Temnospondyls of the Triassic. (a) simplified phylogeny of the temnospondyl clades investigated here, with two paraphyletic assemblages, ’basal temnos’ and basal ’stereos’. Amphibamiformes are a clade within Dissorophoidea, comprising Micropholidae and Lissamphibia. Branches stemming from coloured nodes depict subclades of this node. (b) three functional groupings based on skull morphology: large parabolic skulls characteristic of generalists such as extant crocodilians; generalist insectivore with short and wide skulls as in modern frogs; and longirostrine, adapted for fast, weak bites usually in fish eating, as in modern gharials. Abbreviations: Stereo., Sterospondyli; Temno., Temnospondyli. Silhouette images from Phylopic (https://www.phylopic.org: Dmitry Bogdanov (Metoposaurus, Lydekkerina, Batrachosuchus, Pelorocephalus, Trematosaurus) all CC0 3.0; Steven Traver (Dendrobates) CC0 1.0). Nix Draws Stuff/Nix illustration (Eryops) CC0 4.0. Silhouette images from Wikimedia Commons (https://commons.wikimedia.org: Smokeybjb (Eolydekkerina magna, Deltasaurus kimberleyensis); Nobu Tamura (Gerrothorax BW and Wetlugasaurus BW) all CC0 3.0). Vector graphics: Mike Prince (Gharial) CC0 2.0; Momotarou, 2012 (Andrias japonicus) CC0 3.0; CDC (African Dwarf Frog) Public Domain. Skull Graphics vectorized by AM; Aphaneramma [Fortuny, et al. 2018]; Cyclotosaurus [Schoch & Milner, 2014] and Triadobatrachus [Ascarrunz, et al. 2016]. |
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Mastodonsaurus vs. Jaxtasuchus artwork by Mark P. Witton |
Aamir Mehmood, Suresh A. Singh, Armin Elsler and Michael J. Benton. 2025. The Ecology and Geography of Temnospondyl Recovery after the Permian–Triassic Mass Extinction. R. Soc. Open Sci. 12: 241200. DOI: doi.org/10.1098/rsos.241200 [05 March 2025]
Amphibians bounce-back from Earth’s greatest mass extinction
Ancient frog relatives survived the aftermath of the largest mass extinction of species by feeding on freshwater prey that evaded terrestrial predators, University of Bristol academics have found.
In the study, published today in the journal Royal Society Open Science, their findings suggest the amphibians’ success lay in their generalist feeding ecology, enabling them to feed on a wide variety of prey despite the array of environmental changes happening all around them through the Triassic.
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