Neotenic lifestyles in extant Caudata and Permian temnospondyl Apateon + Stenotosaurus aitoualii, new temnospondyl species from Middle Triassic of Algeria
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Ben Creisler
Oct 1, 2026, 3:41:06 PM (9 days ago) Oct 1
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Ben Creisler
New amphibian papers:
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Free pdf:
Nicole Klein, Dorota Konietzko-Meier, Rainer R. Schoch & Eva M. Griebeler (2026)
Do osteohistology, microanatomy or life history traits show patterns linked to neotenic lifestyles in extant Caudata and the Permian temnospondyl Apateon?
BMC Ecology and Evolution (advance online publication)
doi: https://doi.org/10.1186/s12862-026-02577-x
https://link.springer.com/article/10.1186/s12862-026-02577-x
Neoteny is widespread in extant Caudata and has also been inferred in extinct temnospondyls. Here, we compare osteohistology, microanatomy, and life history traits of the Permian branchiosaurid Apateon spp. with those of modern obligate and facultative neotenic and not neotenic caudates to possibly identify common patterns separating groups. The osteohistology of these modern caudates is studied for the first time based on petrographic ground sections, which yield a better comparability between modern and fossilized bones than microtomized thin sections. We found in all adult individuals’ avascular lamellar matrix, except for Necturus maculosus, which grew with avascular parallel-fibered bone. The presence of osteoblasts indicates prolonged bone mineralization process in caudates. Medullary cavity size varies widely in humeri of Ambystoma mexicanum and in humeri and femora of Apateon spp., whereas in all other taxa it is more uniform and tendentially compacter which, however, might be the result of lower sample sizes. Apateon spp. had numerous lines of arrested growth indicating strong seasonal growth as was described in detail before and which is in accordance with the inferred environmental conditions. The markedness of growth marks is well pronounced in Necturus maculosus, Amphiuma means, Triturus cristatus, Lissotriton vulgaris and Salamandra salamandra but not in others. Poor expression of growth marks might be related to constant climatic conditions (e.g., Ambystoma mexicanum, Proteus anguinus) or due to an early ontogenetic stage and a yet low mineralized matrix of some individuals in our sample (Ichthyosaura alpestris, Calotriton asper). Growth mark counts of captive A. mexicanum of known age considerably underestimated their actual age. The analysis of adult body mass, age at maturation and maximum longevity of a large dataset on obligate neotenic and non-obligate neotenic caudates indicated a high variability in the two latter traits and associations among each other and to adult body mass. Due to this large variability, we did not find any pattern that can be used to unequivocally infer whether a taxon is obligate neotenic or not. Overall, our results suggest that no shared pattern in osteohistology, microanatomy or life history traits exists among extant obligate neotenic, non-obligate neotenic and extinct neotenic Apateon.
Nicole Klein, Dorota Konietzko-Meier, Rainer R. Schoch & Eva M. Griebeler (2026)
Do osteohistology, microanatomy or life history traits show patterns linked to neotenic lifestyles in extant Caudata and the Permian temnospondyl Apateon?
BMC Ecology and Evolution (advance online publication)
doi: https://doi.org/10.1186/s12862-026-02577-x
https://link.springer.com/article/10.1186/s12862-026-02577-x
Neoteny is widespread in extant Caudata and has also been inferred in extinct temnospondyls. Here, we compare osteohistology, microanatomy, and life history traits of the Permian branchiosaurid Apateon spp. with those of modern obligate and facultative neotenic and not neotenic caudates to possibly identify common patterns separating groups. The osteohistology of these modern caudates is studied for the first time based on petrographic ground sections, which yield a better comparability between modern and fossilized bones than microtomized thin sections. We found in all adult individuals’ avascular lamellar matrix, except for Necturus maculosus, which grew with avascular parallel-fibered bone. The presence of osteoblasts indicates prolonged bone mineralization process in caudates. Medullary cavity size varies widely in humeri of Ambystoma mexicanum and in humeri and femora of Apateon spp., whereas in all other taxa it is more uniform and tendentially compacter which, however, might be the result of lower sample sizes. Apateon spp. had numerous lines of arrested growth indicating strong seasonal growth as was described in detail before and which is in accordance with the inferred environmental conditions. The markedness of growth marks is well pronounced in Necturus maculosus, Amphiuma means, Triturus cristatus, Lissotriton vulgaris and Salamandra salamandra but not in others. Poor expression of growth marks might be related to constant climatic conditions (e.g., Ambystoma mexicanum, Proteus anguinus) or due to an early ontogenetic stage and a yet low mineralized matrix of some individuals in our sample (Ichthyosaura alpestris, Calotriton asper). Growth mark counts of captive A. mexicanum of known age considerably underestimated their actual age. The analysis of adult body mass, age at maturation and maximum longevity of a large dataset on obligate neotenic and non-obligate neotenic caudates indicated a high variability in the two latter traits and associations among each other and to adult body mass. Due to this large variability, we did not find any pattern that can be used to unequivocally infer whether a taxon is obligate neotenic or not. Overall, our results suggest that no shared pattern in osteohistology, microanatomy or life history traits exists among extant obligate neotenic, non-obligate neotenic and extinct neotenic Apateon.
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NOTE: The English translation is not yet available, but the Russian original is free in Research Gate.
Free pdf:
Stenotosaurus aitoualii sp. nov.
A. Dahoumane, В. I. Morkovin, A. Nedjari & J. Tellal (2026)
A New Capitosauroid (Amphibia, Temnospondyli) From the Middle Triassic of Algeria
Paleontological Journal 4: 81-97 (Russian edition)
DOI: 10.7868/S3034587126040096
A new capitosauroid temnospondyl species, Stenotosaurus aitoualii sp. nov., has been described from the Tri-assic Zarzaitine Series in south-eastern Algeria (the Reculee site). This taxon exhibits more advanced cranialfeatures than Stanocephalosaurus amenasensis, a species known from numerous finds that occurs in a lowerstratigraphic position within the same section. The high degree of preservation enables the identification ofseveral features, such as contact between the exoccipitale and pterygoideum, the distant position of the recessusconoideus pterygoidei relative to the posterior margin of the pterygoid fenestrae and the steep inclination of thecheek region of the skull. These features are not observable in previously described species of Stenotosaurus,such as S. semiclausus and S. gracilis, from Middle Triassic deposits in Western Europe. The temporal succes-sion of the two capitosauroid taxa (the genera Stanocephalosaurus and Stenotosaurus) from the Reculee section,as established during this study, reflects the transition between two successive faunal stages in the history oflocal tetrapod communities from the late Early to early Middle Triassic
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