Argentinonectes, new elasmosaurid from Upper Cretaceous of Argentina + Champsosaurus and Leidyosuchus skull shapes show resource partitioning
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Ben Creisler
Jun 1, 2026, 1:54:22 PM (5 days ago) Jun 1
to DinosaurMa...@googlegroups.com
Ben Creisler
Argentinonectes calafatensis gen. et sp. nov.
Fernando E. Novas, Julia D’Angelo, Federico Agnolín, Rodrigo Otero , Jordi Garcia Marsà, Silvio Casadio, Kenneth Lacovara & Marcelo Isasi (2026)
New plesiosaur from the uppermost Cretaceous of Patagonia sheds light on thoracic and caudal anatomy in plesiosaurs
Cretaceous Research 106430
doi: https://doi.org/10.1016/j.cretres.2026.106430
https://www.sciencedirect.com/science/article/abs/pii/S0195667126001199
We describe a partial skeleton referred to a new elasmosaurid taxon, Argentinonectes calafatensis gen. et sp. nov., from the Maastrichtian Calafate Formation, SW Argentina. State of preservation of Argentinonectes calafatensis holotype offers new insights into the plesiosaur body plan, including distribution of internal canals along postcervical vertebrae, presence of a stiffened distal end of the tail, orientation of the thoracic ribs, and morphological variations of gastral elements. We present evidence that the system of subcentral foramina and associated internal canals was not restricted to the cervical series, but extended along the entire vertebral column of Argentinonectes. Argentinonectes exhibits a stiffened distal end of the tail formed by the last eight distal-most caudals. Rib anatomy and articulation with the dorsal vertebrae indicates that Argentinonectes had an oblate dorsoventral thorax and pachyostotic gastralia, demonstrating that such features were widely distributed among Jurassic and Cretaceous plesiosaurs. The gastral basket of Argentinonectes shows notable differences in the morphology of single elements per row, probably indicating that some regions of the gastral basket were more freely articulated than others, participating differentially in the respiratory movements of the belly. This discovery enlarges the list of Upper Cretaceous non-aristonectine elasmosaurids from southern South America and Antarctica, which are currently known for incomplete postcranial remains.
New reptile papers:
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Argentinonectes calafatensis gen. et sp. nov.
Fernando E. Novas, Julia D’Angelo, Federico Agnolín, Rodrigo Otero , Jordi Garcia Marsà, Silvio Casadio, Kenneth Lacovara & Marcelo Isasi (2026)
New plesiosaur from the uppermost Cretaceous of Patagonia sheds light on thoracic and caudal anatomy in plesiosaurs
Cretaceous Research 106430
doi: https://doi.org/10.1016/j.cretres.2026.106430
https://www.sciencedirect.com/science/article/abs/pii/S0195667126001199
We describe a partial skeleton referred to a new elasmosaurid taxon, Argentinonectes calafatensis gen. et sp. nov., from the Maastrichtian Calafate Formation, SW Argentina. State of preservation of Argentinonectes calafatensis holotype offers new insights into the plesiosaur body plan, including distribution of internal canals along postcervical vertebrae, presence of a stiffened distal end of the tail, orientation of the thoracic ribs, and morphological variations of gastral elements. We present evidence that the system of subcentral foramina and associated internal canals was not restricted to the cervical series, but extended along the entire vertebral column of Argentinonectes. Argentinonectes exhibits a stiffened distal end of the tail formed by the last eight distal-most caudals. Rib anatomy and articulation with the dorsal vertebrae indicates that Argentinonectes had an oblate dorsoventral thorax and pachyostotic gastralia, demonstrating that such features were widely distributed among Jurassic and Cretaceous plesiosaurs. The gastral basket of Argentinonectes shows notable differences in the morphology of single elements per row, probably indicating that some regions of the gastral basket were more freely articulated than others, participating differentially in the respiratory movements of the belly. This discovery enlarges the list of Upper Cretaceous non-aristonectine elasmosaurids from southern South America and Antarctica, which are currently known for incomplete postcranial remains.
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Free pdf:
Louis-Philippe Bateman, Alexandre V Demers-Potvin & Hans C E Larsson (2026)
Champsosaurs, gharials, and the functional ecomorphology of resource partitioning
Biological Journal of the Linnean Society 148(2): blag027
doi: https://doi.org/10.1093/biolinnean/blag027
https://academic.oup.com/biolinnean/article/148/2/blag027/8698918
Understanding how species interact and partition ecosystems is central to ecology and evolution, yet this remains difficult to test in the fossil record. Here, we examine potential resource partitioning between the Late Cretaceous diapsid Champsosaurus lindoei and the alligatoroid Leidyosuchus canadensis, two sympatric semiaquatic predators from the Dinosaur Park Formation of Alberta, Canada. To interpret their ecological interactions, we compare them with the most analogous extant pair, the gharial (Gavialis gangeticus) and the mugger crocodile (Crocodylus palustris), whose coexistence and dietary differences are well documented. Using 3D reconstructions of skulls and jaw musculature, we estimate ecomorphological performance metrics—including bite force, mandibular inertia, and tooth pressure—validated against the extant predators. Results show that Champsosaurus and Leidyosuchus differed in tooth and skull morphology, mandibular inertia, and bite performance in ways closely paralleling those values for Gavialis and Crocodylus. The estimated ecological distance between both pairs of taxa is also broadly similar. These findings confirm that Champsosaurus occupied a more specialized piscivorous niche, while Leidyosuchus was a generalist predator. Moreover, our approach demonstrates that functional morphology can reveal degrees of resource partitioning in deep time when anchored to extant analogues, providing a framework for reconstructing the ecological structure of ancient communities.
==
Louis-Philippe Bateman, Alexandre V Demers-Potvin & Hans C E Larsson (2026)
Champsosaurs, gharials, and the functional ecomorphology of resource partitioning
Biological Journal of the Linnean Society 148(2): blag027
doi: https://doi.org/10.1093/biolinnean/blag027
https://academic.oup.com/biolinnean/article/148/2/blag027/8698918
Understanding how species interact and partition ecosystems is central to ecology and evolution, yet this remains difficult to test in the fossil record. Here, we examine potential resource partitioning between the Late Cretaceous diapsid Champsosaurus lindoei and the alligatoroid Leidyosuchus canadensis, two sympatric semiaquatic predators from the Dinosaur Park Formation of Alberta, Canada. To interpret their ecological interactions, we compare them with the most analogous extant pair, the gharial (Gavialis gangeticus) and the mugger crocodile (Crocodylus palustris), whose coexistence and dietary differences are well documented. Using 3D reconstructions of skulls and jaw musculature, we estimate ecomorphological performance metrics—including bite force, mandibular inertia, and tooth pressure—validated against the extant predators. Results show that Champsosaurus and Leidyosuchus differed in tooth and skull morphology, mandibular inertia, and bite performance in ways closely paralleling those values for Gavialis and Crocodylus. The estimated ecological distance between both pairs of taxa is also broadly similar. These findings confirm that Champsosaurus occupied a more specialized piscivorous niche, while Leidyosuchus was a generalist predator. Moreover, our approach demonstrates that functional morphology can reveal degrees of resource partitioning in deep time when anchored to extant analogues, providing a framework for reconstructing the ecological structure of ancient communities.
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