"Plesiosaurus" posidoniae identity + Joggins Carboniferous tetrapod fauna found in hollow trees
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Ben Creisler
Mar 7, 2026, 2:18:24 PM (6 days ago) Mar 7
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Ben Creisler
New papers:
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Sven Sachs, Günter Schweigert & Daniel Madzia (2026)
Unraveling the identity of Plesiosaurus posidoniae, the first plesiosaur described from the Posidonia Shale of Germany
The Anatomical Record (advance online publication)
doi: https://doi.org/10.1002/ar.70157
https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.70157
Plesiosaurus posidoniae, described by Quenstedt in 1865, is the first plesiosaur taxon to be named from the lower Toarcian Posidonia Shale (Posidonienschiefer Formation) of Germany. The holotype consists of a fragmentary left hind limb, comprising the femur, tibia, tarsal and metatarsal elements, and phalanges, found at Reutlingen-Ohmenhausen in southwestern Germany. Despite its historical significance, the taxonomic affinities of P. posidoniae remain unexplored. Although fragmentary, the specimen shows characters useful for its taxonomic assessment, including the proportions of the femur and tibia, the uniformly rounded distal femoral end, and the lack of an intermedium facet at the tibia. Osteological comparisons, combined with multivariate analyses incorporating continuous and discrete data obtained from paddle elements of Posidonia Shale plesiosaurs, indicate great similarities and probable affinities with the early-diverging pliosaurid Hauffiosaurus. However, differences can also be observed, such as the greater slenderness of the femora of Hauffiosaurus. These differences may reflect intraspecific variability, but the fragmentary nature of P. posidoniae prevents an unequivocal taxonomic assignment.
Sven Sachs, Günter Schweigert & Daniel Madzia (2026)
Unraveling the identity of Plesiosaurus posidoniae, the first plesiosaur described from the Posidonia Shale of Germany
The Anatomical Record (advance online publication)
doi: https://doi.org/10.1002/ar.70157
https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.70157
Plesiosaurus posidoniae, described by Quenstedt in 1865, is the first plesiosaur taxon to be named from the lower Toarcian Posidonia Shale (Posidonienschiefer Formation) of Germany. The holotype consists of a fragmentary left hind limb, comprising the femur, tibia, tarsal and metatarsal elements, and phalanges, found at Reutlingen-Ohmenhausen in southwestern Germany. Despite its historical significance, the taxonomic affinities of P. posidoniae remain unexplored. Although fragmentary, the specimen shows characters useful for its taxonomic assessment, including the proportions of the femur and tibia, the uniformly rounded distal femoral end, and the lack of an intermedium facet at the tibia. Osteological comparisons, combined with multivariate analyses incorporating continuous and discrete data obtained from paddle elements of Posidonia Shale plesiosaurs, indicate great similarities and probable affinities with the early-diverging pliosaurid Hauffiosaurus. However, differences can also be observed, such as the greater slenderness of the femora of Hauffiosaurus. These differences may reflect intraspecific variability, but the fragmentary nature of P. posidoniae prevents an unequivocal taxonomic assignment.
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Free pdf:
John H. Calder, Andrew C. Scott, Brian L. Hebert, Andrew C. Milner & Matthew R. Stimson (2026)
Carboniferous tetrapod fauna of the fossil lycopsid trees at Joggins and the origin of the hollow tree guild
Proceedings of the Geologists' Association 101177
doi: https://doi.org/10.1016/j.pgeola.2026.101177
https://www.sciencedirect.com/science/article/pii/S0016787826000179
In their 1853 paper announcing the discovery of fossil tetrapods in the once-hollow trees at Joggins, Nova Scotia, Lyell and Dawson gave three possibilities for their entombment: the tetrapods may have been washed in after death, entered via a ‘crevice’ in the trunk, or fallen into partially buried, hollow trunks. The latter scenario, or ‘pitfall theory’, grew to be favoured by Dawson and to be depicted in most texts on the history of life, but is here scrutinized following recent discoveries by the authors and re-evaluation of historic finds. Nominally eleven tetrapod taxa have been identified from the fossil trees, including the earliest known amniotes — the richest single Carboniferous record of terrestrial tetrapods. Tetrapods co-occur with detrivorous invertebrates (land snails and millipedes), as well as putative insects. Here, we systematically evaluate scenarios for the occurrence of the tetrapod fauna, including accidental entry (pitfall, being washed in); temporary, opportunistic use (by predator, as refuge from fire); and denning. These scenarios have been weighed against salient aspects of their taphonomy, including their entry prior to infilling, disassembled skeletons, and ubiquitous association with charcoal. The broader role of wildfire is suggested by discovery of a tetrapod-bearing lycopsid with notched, charred base consistent with a fire scar, the oldest such example in the fossil record. Of the scenarios scrutinized, the most parsimonious is that tetrapods utilized lycopsid hollows as dens; compelling analogues are found in tree hollow fauna of modern forest biomes, many of which use fire scars as entry. Temporal shifts to seasonal, fire-prone drylands may have exerted ecological pressure on the Joggins fauna to avail themselves of tree hollows whilst providing access via fire scars. The tetrapod fauna at Joggins, which includes the earliest amniote, records the earliest known example of the hollow tree guild, well adapted to the ecological dynamics of the ‘Coal Age’ landscape.
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Carboniferous tetrapod fauna of the fossil lycopsid trees at Joggins and the origin of the hollow tree guild
Proceedings of the Geologists' Association 101177
doi: https://doi.org/10.1016/j.pgeola.2026.101177
https://www.sciencedirect.com/science/article/pii/S0016787826000179
In their 1853 paper announcing the discovery of fossil tetrapods in the once-hollow trees at Joggins, Nova Scotia, Lyell and Dawson gave three possibilities for their entombment: the tetrapods may have been washed in after death, entered via a ‘crevice’ in the trunk, or fallen into partially buried, hollow trunks. The latter scenario, or ‘pitfall theory’, grew to be favoured by Dawson and to be depicted in most texts on the history of life, but is here scrutinized following recent discoveries by the authors and re-evaluation of historic finds. Nominally eleven tetrapod taxa have been identified from the fossil trees, including the earliest known amniotes — the richest single Carboniferous record of terrestrial tetrapods. Tetrapods co-occur with detrivorous invertebrates (land snails and millipedes), as well as putative insects. Here, we systematically evaluate scenarios for the occurrence of the tetrapod fauna, including accidental entry (pitfall, being washed in); temporary, opportunistic use (by predator, as refuge from fire); and denning. These scenarios have been weighed against salient aspects of their taphonomy, including their entry prior to infilling, disassembled skeletons, and ubiquitous association with charcoal. The broader role of wildfire is suggested by discovery of a tetrapod-bearing lycopsid with notched, charred base consistent with a fire scar, the oldest such example in the fossil record. Of the scenarios scrutinized, the most parsimonious is that tetrapods utilized lycopsid hollows as dens; compelling analogues are found in tree hollow fauna of modern forest biomes, many of which use fire scars as entry. Temporal shifts to seasonal, fire-prone drylands may have exerted ecological pressure on the Joggins fauna to avail themselves of tree hollows whilst providing access via fire scars. The tetrapod fauna at Joggins, which includes the earliest amniote, records the earliest known example of the hollow tree guild, well adapted to the ecological dynamics of the ‘Coal Age’ landscape.
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