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Deinosuchus as stem-crocodylian, not alligatoroid + turtle assemblage from Upper Cretaceous Menefee Formation in New Mexico (free pdfs)
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Ben Creisler
Apr 23, 2025, 10:36:08 AMApr 23
to DinosaurMa...@googlegroups.com
Ben Creisler
Jules D. Walter, Tobias Massonne, Ana Laura S. Paiva, Jeremy E. Martin, Massimo Delfino & Márton Rabi (2025)
Expanded phylogeny elucidates Deinosuchus relationships, crocodylian osmoregulation and body-size evolution
Communications Biology 8: 611
doi: https://doi.org/10.1038/s42003-025-07653-4
https://www.nature.com/articles/s42003-025-07653-4
Transmarine distribution and gigantism in the Late Cretaceous North American crocodyliform Deinosuchus has been difficult to reconcile with consistently inferred phylogenetic relationships to alligatorids, an otherwise freshwater and smaller-bodied group. We present an expanded phylogeny with increased spatiotemporally coherence that reinterprets species of Deinosuchus as stem-group crocodylians together with further putative alligatoroids, Leidyosuchus canadensis and the European Diplocynodon spp. (closely related to North American Borealosuchus). The novel topology elucidates the evolution of osmoregulation in Crocodylia and its close relatives by inferring plesiomorphic saltwater tolerance for Deinosuchus and the crown-group as well as secondary loss already in stem-group alligatorids. Divergence of Alligatoroidea coincided with extreme mid-Cretaceous sea level highs and the distribution of Deinosuchus across the Western Interior Seaway can be best explained by marine dispersal. Phylogenetic body-length analysis using a head-width proxy reveals phyletic dwarfism early in alligatoroid evolution and a reasonable total length estimate for the most complete specimen of Deinosuchus riograndensis. We find that gigantism in crocodyliforms is correlated with high-productive extensive aquatic ecosystems in the present and the past.
====
Brent Adrian, Heather F. Smith & Andrew T. McDonald (2025)
A revised turtle assemblage from the Upper Cretaceous Menefee Formation (New Mexico, North America) with evolutionary and paleobiostratigraphic implications.
PeerJ 13: e19340
doi: https://doi.org/10.7717/peerj.19340
https://peerj.com/articles/19340/
The middle Campanian Menefee Formation (Fm.) of the San Juan Basin of New Mexico is a relatively understudied terrestrial deposit in southern Laramidia preceding the fossil-rich upper Campanian Fruitland and Kirtland formations that have been studied for more than a century. Previous collection efforts have revealed a diverse dinosaurian and crocodyliform fauna in the Menefee Fm., including ankylosaurian, tyrannosaurid, hadrosaurid, ceratopsian, and neosuchian taxa. Nearly a decade has passed since the last description of the Menefee turtle fauna, and we present new material that provides insight into turtle evolution during the Campanian in the Colorado Plateau, with implications for Late Cretaceous turtle paleobiostratigraphy in Laramidia. In particular, we extend the stratigraphic ranges of the baenids Neurankylus baueri and Scabremys ornata backwards from younger San Juan Basin strata, along with the nanhsiungchelyid Basilemys. Additional material increases Menefee representation of the relict helochelydrid Naomichelys, and the regionally prevalent derived baenids Denazinemys and Thescelus. Additionally, we report new pan-trionychian specimens, which provide insight into the persistence of Adocus and multiple trionychid and plastomenid species through the remainder of the Campanian in the San Juan Basin. A cluster analysis of turtle diversity across early-middle Campanian sites in Laramidia shows distributions consistent with latitudinal provinciality in some groups. For instance, derived baenids were restricted to latitudes south of southern Utah, along with marine taxa (bothremydids and protostegids) and pan-kinosternoids. Basin-scale endemism is also suggested by some baenid and trionychid distributions. Otherwise, the turtle fauna of the Menefee most closely resemble those of the similarly-aged Wahweap Fm. in southern Utah, and the Aguja Fm. in the Big Bend area of Texas and Mexico to a lesser extent. The Menefee turtle assemblage is consistent with reconstructed paleoenvironments characteristic of the western shoreline of the Western Interior Seaway. Recurrent cyclothems in these settings shaped the development of fluviodeltaic deposits that preserved distal components of large channels with surrounding floodplains and swamps, along with evidence of freshwater, brackish, and possibly shallow marine influence.
====
New papers:
Free pdf:
Jules D. Walter, Tobias Massonne, Ana Laura S. Paiva, Jeremy E. Martin, Massimo Delfino & Márton Rabi (2025)
Expanded phylogeny elucidates Deinosuchus relationships, crocodylian osmoregulation and body-size evolution
Communications Biology 8: 611
doi: https://doi.org/10.1038/s42003-025-07653-4
https://www.nature.com/articles/s42003-025-07653-4
Transmarine distribution and gigantism in the Late Cretaceous North American crocodyliform Deinosuchus has been difficult to reconcile with consistently inferred phylogenetic relationships to alligatorids, an otherwise freshwater and smaller-bodied group. We present an expanded phylogeny with increased spatiotemporally coherence that reinterprets species of Deinosuchus as stem-group crocodylians together with further putative alligatoroids, Leidyosuchus canadensis and the European Diplocynodon spp. (closely related to North American Borealosuchus). The novel topology elucidates the evolution of osmoregulation in Crocodylia and its close relatives by inferring plesiomorphic saltwater tolerance for Deinosuchus and the crown-group as well as secondary loss already in stem-group alligatorids. Divergence of Alligatoroidea coincided with extreme mid-Cretaceous sea level highs and the distribution of Deinosuchus across the Western Interior Seaway can be best explained by marine dispersal. Phylogenetic body-length analysis using a head-width proxy reveals phyletic dwarfism early in alligatoroid evolution and a reasonable total length estimate for the most complete specimen of Deinosuchus riograndensis. We find that gigantism in crocodyliforms is correlated with high-productive extensive aquatic ecosystems in the present and the past.
====
Free pdf:
Brent Adrian, Heather F. Smith & Andrew T. McDonald (2025)
A revised turtle assemblage from the Upper Cretaceous Menefee Formation (New Mexico, North America) with evolutionary and paleobiostratigraphic implications.
PeerJ 13: e19340
doi: https://doi.org/10.7717/peerj.19340
https://peerj.com/articles/19340/
The middle Campanian Menefee Formation (Fm.) of the San Juan Basin of New Mexico is a relatively understudied terrestrial deposit in southern Laramidia preceding the fossil-rich upper Campanian Fruitland and Kirtland formations that have been studied for more than a century. Previous collection efforts have revealed a diverse dinosaurian and crocodyliform fauna in the Menefee Fm., including ankylosaurian, tyrannosaurid, hadrosaurid, ceratopsian, and neosuchian taxa. Nearly a decade has passed since the last description of the Menefee turtle fauna, and we present new material that provides insight into turtle evolution during the Campanian in the Colorado Plateau, with implications for Late Cretaceous turtle paleobiostratigraphy in Laramidia. In particular, we extend the stratigraphic ranges of the baenids Neurankylus baueri and Scabremys ornata backwards from younger San Juan Basin strata, along with the nanhsiungchelyid Basilemys. Additional material increases Menefee representation of the relict helochelydrid Naomichelys, and the regionally prevalent derived baenids Denazinemys and Thescelus. Additionally, we report new pan-trionychian specimens, which provide insight into the persistence of Adocus and multiple trionychid and plastomenid species through the remainder of the Campanian in the San Juan Basin. A cluster analysis of turtle diversity across early-middle Campanian sites in Laramidia shows distributions consistent with latitudinal provinciality in some groups. For instance, derived baenids were restricted to latitudes south of southern Utah, along with marine taxa (bothremydids and protostegids) and pan-kinosternoids. Basin-scale endemism is also suggested by some baenid and trionychid distributions. Otherwise, the turtle fauna of the Menefee most closely resemble those of the similarly-aged Wahweap Fm. in southern Utah, and the Aguja Fm. in the Big Bend area of Texas and Mexico to a lesser extent. The Menefee turtle assemblage is consistent with reconstructed paleoenvironments characteristic of the western shoreline of the Western Interior Seaway. Recurrent cyclothems in these settings shaped the development of fluviodeltaic deposits that preserved distal components of large channels with surrounding floodplains and swamps, along with evidence of freshwater, brackish, and possibly shallow marine influence.
====
Jura
Apr 24, 2025, 3:02:32 PMApr 24
to Dinosaur Mailing Group
Some news items related to this new, unique placement of Deinosuchus.
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