Thoracosaurus (longirostrine crocodylian) redescribed + aridity in Late Triassic Greenland dinosaur ecosystem
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Ben Creisler
Feb 10, 2026, 1:30:39 PM (2 days ago) Feb 10
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Ben Creisler
New papers:
Sophie A. C. M. Boerman, Johan Vellekoop, Stéphane Jouve, Márton Rabi, Nathan Vallée-Gillette, Thierry Oudoire & Thierry Smith (2026)
Revision of the longirostrine crocodylian Thoracosaurus isorhynchus from the Maastrichtian–Danian of northwestern Europe
Journal of Vertebrate Paleontology e2604600
doi: https://doi.org/10.1080/02724634.2025.2604600
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2604600
A highly debated topic in eusuchian systematics has been the placement of “thoracosaurs,” an assemblage of Cretaceous–Paleogene longirostrine crocodylians from Europe and North America. The position of “thoracosaurs” varies from one study to the next, from being the sister taxon of the extant Gavialis to being excluded from the crown group Crocodylia entirely. Despite these issues, “thoracosaurs” have been understudied, with many taxa suffering from incomplete or outdated descriptions and dubious taxonomic assignment. Here, we provide a comprehensive study of Thoracosaurus isorhynchus from Maastrichtian–Danian deposits of northwestern Europe. We present and describe new material from the type locality of T. isorhynchus. In addition, we redescribe and figure the lectotype and paralectotypes of the species, as well as the material from the Maastrichtian type area, the Netherlands. Moreover, comparison of T. isorhynchus with the type material of Thoracosaurus “scanicus” of the Danian of southern Sweden indicates that the latter might be a junior synonym of T. isorhynchus, suggesting the survival of this species across the Cretaceous–Paleogene boundary. An array of phylogenetic analyses points to a close relationship between T. isorhynchus and the Cenomanian Portugalosuchus azenhae. This implies an early emergence of “thoracosaurs” and causes extensive ghost lineages within Gavialoidea, highlighting the stratigraphic inconsistency of this group and a need for a thorough revision of other “thoracosaurs.”
Sophie A. C. M. Boerman, Johan Vellekoop, Stéphane Jouve, Márton Rabi, Nathan Vallée-Gillette, Thierry Oudoire & Thierry Smith (2026)
Revision of the longirostrine crocodylian Thoracosaurus isorhynchus from the Maastrichtian–Danian of northwestern Europe
Journal of Vertebrate Paleontology e2604600
doi: https://doi.org/10.1080/02724634.2025.2604600
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2604600
A highly debated topic in eusuchian systematics has been the placement of “thoracosaurs,” an assemblage of Cretaceous–Paleogene longirostrine crocodylians from Europe and North America. The position of “thoracosaurs” varies from one study to the next, from being the sister taxon of the extant Gavialis to being excluded from the crown group Crocodylia entirely. Despite these issues, “thoracosaurs” have been understudied, with many taxa suffering from incomplete or outdated descriptions and dubious taxonomic assignment. Here, we provide a comprehensive study of Thoracosaurus isorhynchus from Maastrichtian–Danian deposits of northwestern Europe. We present and describe new material from the type locality of T. isorhynchus. In addition, we redescribe and figure the lectotype and paralectotypes of the species, as well as the material from the Maastrichtian type area, the Netherlands. Moreover, comparison of T. isorhynchus with the type material of Thoracosaurus “scanicus” of the Danian of southern Sweden indicates that the latter might be a junior synonym of T. isorhynchus, suggesting the survival of this species across the Cretaceous–Paleogene boundary. An array of phylogenetic analyses points to a close relationship between T. isorhynchus and the Cenomanian Portugalosuchus azenhae. This implies an early emergence of “thoracosaurs” and causes extensive ghost lineages within Gavialoidea, highlighting the stratigraphic inconsistency of this group and a need for a thorough revision of other “thoracosaurs.”
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Wojciech Pawlak, Mateusz Tałanda, Tomasz Sulej, Martin Qvarnström & Grzegorz Niedźwiedzki (2026)
High-latitude dipnoan aestivation burrows suggest seasonal aridity for early dinosaur ecosystems in the Late Triassic of East Greenland
Palaeogeography, Palaeoclimatology, Palaeoecology 113624
doi: https://doi.org/10.1016/j.palaeo.2026.113624
https://www.sciencedirect.com/science/article/abs/pii/S0031018226000878
Highlights
First record of large burrows from the Fleming Fjord Group in Jameson Land, East Greenland.
Burrows are interpreted as dipnoan fish aestivation structures.
The discovered trace fossils suggest the seasonally dry climate persisted in the Jameson Land Basin throughout the latest Norian.
Large herbivorous dinosaurs were present in that area despite the dry seasons.
Abstract
It has been proposed that arid conditions across certain regions in Pangea limited the migration of herbivorous dinosaurs. However, there is conflicting evidence about the prevailing climatic conditions in northern Pangea, an area inhabited by large sauropodomorphs from the mid-Norian. Here we describe large burrows from the upper part of the Fleming Fjord Group in Jameson Land, East Greenland. They consist of vertical to slightly inclined burrows, up to 60 cm long and 5–10 cm wide, with slightly enlarged terminal chambers. The burrows are identified in mudstone sequences at two separate sites that represent the same interval of the Ørsted Dal Formation. The burrows are unbranched, largely devoid of scratch marks, and have no mud or lag linings. Their large size indicates a vertebrate producer, and due to their morphology and architecture, we interpret them as dipnoan fish aestivation burrows – a shelter in an environment that occasionally dried up. The newly discovered trace fossils lead us to following conclusions: (1) aestivation behaviors were more common amongst non-lepidosirenid lungfish than previously assumed, (2) a seasonally dry climate persisted in the Jameson Land Basin throughout the latest Norian, (3) sauropodomorphs and theropods inhabited the area despite the dry conditions, and thus (4) the spatial distribution of sauropodomorphs was perhaps controlled by factors other than aridity or, alternatively, they migrated to this area only seasonally.
High-latitude dipnoan aestivation burrows suggest seasonal aridity for early dinosaur ecosystems in the Late Triassic of East Greenland
Palaeogeography, Palaeoclimatology, Palaeoecology 113624
doi: https://doi.org/10.1016/j.palaeo.2026.113624
https://www.sciencedirect.com/science/article/abs/pii/S0031018226000878
Highlights
First record of large burrows from the Fleming Fjord Group in Jameson Land, East Greenland.
Burrows are interpreted as dipnoan fish aestivation structures.
The discovered trace fossils suggest the seasonally dry climate persisted in the Jameson Land Basin throughout the latest Norian.
Large herbivorous dinosaurs were present in that area despite the dry seasons.
Abstract
It has been proposed that arid conditions across certain regions in Pangea limited the migration of herbivorous dinosaurs. However, there is conflicting evidence about the prevailing climatic conditions in northern Pangea, an area inhabited by large sauropodomorphs from the mid-Norian. Here we describe large burrows from the upper part of the Fleming Fjord Group in Jameson Land, East Greenland. They consist of vertical to slightly inclined burrows, up to 60 cm long and 5–10 cm wide, with slightly enlarged terminal chambers. The burrows are identified in mudstone sequences at two separate sites that represent the same interval of the Ørsted Dal Formation. The burrows are unbranched, largely devoid of scratch marks, and have no mud or lag linings. Their large size indicates a vertebrate producer, and due to their morphology and architecture, we interpret them as dipnoan fish aestivation burrows – a shelter in an environment that occasionally dried up. The newly discovered trace fossils lead us to following conclusions: (1) aestivation behaviors were more common amongst non-lepidosirenid lungfish than previously assumed, (2) a seasonally dry climate persisted in the Jameson Land Basin throughout the latest Norian, (3) sauropodomorphs and theropods inhabited the area despite the dry conditions, and thus (4) the spatial distribution of sauropodomorphs was perhaps controlled by factors other than aridity or, alternatively, they migrated to this area only seasonally.
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