Lepidosauria history and relationships + tetrapod cololite from Permian lagoon in Russia
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Ben Creisler
Sep 11, 2026, 1:23:41 PMSep 11
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Ben Creisler
Recent papers:
Susan E. Evans (2026)
Lepidosauria: history and relationships
Journal of Systematic Palaeontology 24(2): 2711806
doi: https://doi.org/10.1080/14772019.2026.2711806
https://www.tandfonline.com/doi/full/10.1080/14772019.2026.2711806
Free pdf:
https://www.tandfonline.com/doi/epdf/10.1080/14772019.2026.2711806
Lepidosauria encompasses Rhynchocephalia (the New Zealand tuatara and its fossil relatives) and Squamata (lizards and snakes), lineages that diverged from one another around 240 million years ago. During the Triassic, Rhynchocephalia dominated the lepidosaur fossil record, radiating globally and remaining successful into the early Cretaceous. By the late Cretaceous, however, rhynchocephalians had disappeared from Laurasia, but recent discoveries in South America and India are suggestive of a late Cretaceous/Palaeogene Gondwanan radiation waiting to be discovered. The squamate fossil record is strikingly different. The first unequivocal pan-squamates are currently from the mid-Jurassic, the first plausible crown-squamates from the late Jurassic, and the first snakes are from the Albian–Cenomanian. However, although the Jurassic and, particularly, early Cretaceous squamate record has improved significantly in recent years, many of these squamate taxa have proved difficult to place securely in a phylogeny. This lack of resolution limits our ability to trace the history and morphological diversification of extant clades, or of extinct ones like polyglyphanodontians and mosasaurians. It stems partly from gaps in the fossil record and/or preservational limitations in existing specimens, partly from a lack of clear osteological discriminators for the stem members of clades, and partly from the fact that molecular analyses have transformed the systematic framework into which fossil taxa are incorporated, leaving phenotypic data struggling to compete with molecular and genomic data. The last of these is a particular challenge for palaeontologists working on the roots of extant clades.
Anton V. Uliakhin, Alexandr S. Bakaev, Andrey V. Podlesnov & Farhad B. Isakhodjaev (2026)
The first tetrapod cololite from a middle Permian lagoon community in European Russia and its implications for palaeoecological reconstruction
Papers in Palaeontology 12(5): e70127
doi: https://doi.org/10.1002/spp2.70127
https://onlinelibrary.wiley.com/doi/10.1002/spp2.70127
The first find of a tetrapod cololite from the middle Permian (Guadalupian) Kazanian stage of European Russia (Shikhovo–Chirki locality, Kirov Region) is described. Inside the incomplete postcranial skeleton we found fossilized material in the gastrointestinal tract with remains of the actinopterygian Kazanichthys viatkensis. According to morphology based on computed tomography 3D reconstruction, microanatomy and histology of the postcranial remains, we suggest that the cololite producer could have been the reptiliomorph gephyrostegid Nyctiboetus kassini. According to our palaeoecological reconstruction, Nyctiboetus was an inhabitant of a desalinated shallow lagoon. The trophic preferences of Nyctiboetus correspond to ichthyophagous predators. What is especially important is that the initially assumed sclerophagy of Nyctiboetus is not the only possible option for feeding behaviour when reconstructing feeding patterns. Small reptiliomorphs of the Shikhovo–Chirki palaeocommunity were adapted to an amphibious lifestyle and fish-hunting in the inner coastal area. This expands our understanding of the biocenotic relationships of the Middle Permian relict gephyrostegids, and is an important addition to the palaeoecology of the ancient tetrapods.
Free pdf:
Susan E. Evans (2026)
Lepidosauria: history and relationships
Journal of Systematic Palaeontology 24(2): 2711806
doi: https://doi.org/10.1080/14772019.2026.2711806
https://www.tandfonline.com/doi/full/10.1080/14772019.2026.2711806
Free pdf:
https://www.tandfonline.com/doi/epdf/10.1080/14772019.2026.2711806
Lepidosauria encompasses Rhynchocephalia (the New Zealand tuatara and its fossil relatives) and Squamata (lizards and snakes), lineages that diverged from one another around 240 million years ago. During the Triassic, Rhynchocephalia dominated the lepidosaur fossil record, radiating globally and remaining successful into the early Cretaceous. By the late Cretaceous, however, rhynchocephalians had disappeared from Laurasia, but recent discoveries in South America and India are suggestive of a late Cretaceous/Palaeogene Gondwanan radiation waiting to be discovered. The squamate fossil record is strikingly different. The first unequivocal pan-squamates are currently from the mid-Jurassic, the first plausible crown-squamates from the late Jurassic, and the first snakes are from the Albian–Cenomanian. However, although the Jurassic and, particularly, early Cretaceous squamate record has improved significantly in recent years, many of these squamate taxa have proved difficult to place securely in a phylogeny. This lack of resolution limits our ability to trace the history and morphological diversification of extant clades, or of extinct ones like polyglyphanodontians and mosasaurians. It stems partly from gaps in the fossil record and/or preservational limitations in existing specimens, partly from a lack of clear osteological discriminators for the stem members of clades, and partly from the fact that molecular analyses have transformed the systematic framework into which fossil taxa are incorporated, leaving phenotypic data struggling to compete with molecular and genomic data. The last of these is a particular challenge for palaeontologists working on the roots of extant clades.
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Anton V. Uliakhin, Alexandr S. Bakaev, Andrey V. Podlesnov & Farhad B. Isakhodjaev (2026)
The first tetrapod cololite from a middle Permian lagoon community in European Russia and its implications for palaeoecological reconstruction
Papers in Palaeontology 12(5): e70127
doi: https://doi.org/10.1002/spp2.70127
https://onlinelibrary.wiley.com/doi/10.1002/spp2.70127
The first find of a tetrapod cololite from the middle Permian (Guadalupian) Kazanian stage of European Russia (Shikhovo–Chirki locality, Kirov Region) is described. Inside the incomplete postcranial skeleton we found fossilized material in the gastrointestinal tract with remains of the actinopterygian Kazanichthys viatkensis. According to morphology based on computed tomography 3D reconstruction, microanatomy and histology of the postcranial remains, we suggest that the cololite producer could have been the reptiliomorph gephyrostegid Nyctiboetus kassini. According to our palaeoecological reconstruction, Nyctiboetus was an inhabitant of a desalinated shallow lagoon. The trophic preferences of Nyctiboetus correspond to ichthyophagous predators. What is especially important is that the initially assumed sclerophagy of Nyctiboetus is not the only possible option for feeding behaviour when reconstructing feeding patterns. Small reptiliomorphs of the Shikhovo–Chirki palaeocommunity were adapted to an amphibious lifestyle and fish-hunting in the inner coastal area. This expands our understanding of the biocenotic relationships of the Middle Permian relict gephyrostegids, and is an important addition to the palaeoecology of the ancient tetrapods.
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