Sharks as apex predators in Late Cretaceous Western Interior Seaway + Purgatorius from Paleocene of Colorado + therian carnivore mandibular function (free pdfs)
69 views
Skip to first unread message
Ben Creisler
Mar 3, 2026, 2:07:13 PM (10 days ago) Mar 3
to DinosaurMa...@googlegroups.com
Ben Creisler
Free pdf:
Jeremy McCormack, Harry Maisch IV, Martin A. Becker, Michael L. Griffiths, Jade Knighton, Robert A. Eagle, Kevin Stevens, Wolfgang Müller & Kenshu Shimada (2026)
Sharks as apex predators in the Late Cretaceous Western Interior Seaway empirically revealed by zinc isotope analyses
Gondwana Research (advance online publication)
doi: https://doi.org/10.1016/j.gr.2026.01.022
https://www.sciencedirect.com/science/article/pii/S1342937X26000626
Highlights
Enamel(oid) δ66Zn values are well preserved in Late Cretaceous marine vertebrates.
Zinc isotopes reveal significant resource partitioning among Cretaceous marine taxa.
Late Cretaceous sharks occupied top trophic positions comparable to today.
Abstract
Food web structures and trophic interactions among Late Cretaceous marine taxa remain largely ambiguous due to the challenges in reconstructing ecological interactions in the deep-time fossil record. Here we analyse enamel(oid) δ66Zn values, a trophic-level proxy, across 16 marine vertebrate taxa from two Turonian–Coniacian boundary localities in New Mexico and Kansas, USA, deposited in what was then the Western Interior Seaway (WIS). Our results demonstrate well-preserved enamel(oid) δ66Zn values in both localities, but locality-specific differences in the diagenetic modification of dentine δ66Zn values. We highlight significant resource partitioning among the analysed taxa within the WIS, including sharks. For example, Archaeolamna, Cretodus and Cretoxyrhina occupied very high trophic positions, whereas Cretalamna was likely foraging opportunistically across several trophic levels. Our study expands the use of enamel(oid) δ66Zn analysis to Mesozoic fossils for the first time and demonstrates that robust reconstructions of food web dynamics and trophic interactions are possible in deep time as far back as 90 million years ago, providing new avenues for palaeobiological and evolutionary research.
=====
Free pdf:
Charles J. Salcido & P. David Polly (2026)
Parallelism of mandibular function in therian carnivores: a morphometric, phylogenetic, and finite element analysis
Paleobiology 52(1): 104 - 120
DOI: https://doi.org/10.1017/pab.2025.10068
https://www.cambridge.org/core/journals/paleobiology/article/parallelism-of-mandibular-function-in-therian-carnivores-a-morphometric-phylogenetic-and-finite-element-analysis/5775F2C350A864CE3C324D882D64EFD5
The evolution of the mandible in mammalian carnivores is influenced by ecological demands that have changed over their phylogenetic history. We combined geometric morphometrics and biomechanical analysis (including beam analysis and finite element analysis, or FEA) to assess the interaction between form and function as the mandible has adapted independently to carnivorous diets in therian clades including Metatheria, Mesonychia, “Creodonta,” and Carnivoramorpha. Our goal was to determine the relative contributions of mechanical advantage, mandibular force, and mandibular resistance to bending and torsion, to the evolution of mandibular shape in these groups, as well as whether they produce differential rates of shape evolution in the horizontal and ascending rami, which respectively are the tooth-bearing and muscle-loading parts of the structure.
We found that the ascending ramus has higher rates of evolution than the horizontal ramus, making it the more rapidly evolvable portion of the mandible. Statistical evaluation supports this interpretation, as mechanical advantage and resistance to force explain more of the variance in shape than do the beam mechanic estimates that are heavily influenced by the mandibular body. Regression analysis shows that the evolution of specialized carnivory was associated with stronger mandibles in which mandibular shape changed by shortening and thickening of the mandible, increasing the areas of muscle attachment, and increasing the carnassial blade length. Principal component analysis of mandibular shape shows that different clades in Theria have been able to fill out similar specialized carnivorous niches with similar functional metrics despite having different mandibular morphologies.
=====
Recent non-dino papers:
Free pdf:
Jeremy McCormack, Harry Maisch IV, Martin A. Becker, Michael L. Griffiths, Jade Knighton, Robert A. Eagle, Kevin Stevens, Wolfgang Müller & Kenshu Shimada (2026)
Sharks as apex predators in the Late Cretaceous Western Interior Seaway empirically revealed by zinc isotope analyses
Gondwana Research (advance online publication)
doi: https://doi.org/10.1016/j.gr.2026.01.022
https://www.sciencedirect.com/science/article/pii/S1342937X26000626
Highlights
Enamel(oid) δ66Zn values are well preserved in Late Cretaceous marine vertebrates.
Zinc isotopes reveal significant resource partitioning among Cretaceous marine taxa.
Late Cretaceous sharks occupied top trophic positions comparable to today.
Abstract
Food web structures and trophic interactions among Late Cretaceous marine taxa remain largely ambiguous due to the challenges in reconstructing ecological interactions in the deep-time fossil record. Here we analyse enamel(oid) δ66Zn values, a trophic-level proxy, across 16 marine vertebrate taxa from two Turonian–Coniacian boundary localities in New Mexico and Kansas, USA, deposited in what was then the Western Interior Seaway (WIS). Our results demonstrate well-preserved enamel(oid) δ66Zn values in both localities, but locality-specific differences in the diagenetic modification of dentine δ66Zn values. We highlight significant resource partitioning among the analysed taxa within the WIS, including sharks. For example, Archaeolamna, Cretodus and Cretoxyrhina occupied very high trophic positions, whereas Cretalamna was likely foraging opportunistically across several trophic levels. Our study expands the use of enamel(oid) δ66Zn analysis to Mesozoic fossils for the first time and demonstrates that robust reconstructions of food web dynamics and trophic interactions are possible in deep time as far back as 90 million years ago, providing new avenues for palaeobiological and evolutionary research.
=====
[It is supposed to be free access. Currently, it can be read online but not downloaded as far as I can tell.]
Free pdf:
Stephen G. B. Chester, Jordan W. Crowell, David W. Krause & Tyler R. Lyson (2026)
Southernmost occurrence of Purgatorius sheds light on the biogeographic history and diversification of the earliest primate relatives
Journal of Vertebrate Paleontology e2614024
doi: https://doi.org/10.1080/02724634.2026.2614024
https://www.tandfonline.com/doi/full/10.1080/02724634.2026.2614024
Free pdf:
https://www.tandfonline.com/doi/epdf/10.1080/02724634.2026.2614024
Fossils of the earliest known euarchontan mammals, purgatoriid plesiadapiforms, first appear during the aftermath of the Cretaceous/Paleogene mass extinction. The oldest and most basally branching plesiadapiform, Purgatorius, has been documented in Montana and Saskatchewan during the earliest Paleocene Puercan North American Land Mammal Age, but no plesiadapiforms have been recovered from southern basins of the Western Interior until later in the Paleocene. This temporal and geographic gap has made the early biogeographic history and diversification patterns of plesiadapiforms unclear. Here we report Purgatorius fossils recovered from extensive screen-washing of sediments from the Corral Bluffs study area, Denver Basin, Colorado, which represent the first Puercan occurrence of a plesiadapiform south of Montana. Isolated teeth of Purgatorius described here exhibit a unique combination of features, and may represent a new, early diverging species. This discovery bridges the temporal and geographic gap among the earliest plesiadapiforms and suggests a northern origin followed by a southerly diversification in the earliest Paleocene. The presumed absence of Puercan plesiadapiforms in southern regions of the Western Interior of North America was at least in part due to sampling biases. Additional screen-washing efforts in these regions will further clarify biogeographic patterns of plesiadapiforms and other small-bodied earliest Paleocene mammals.
====
Stephen G. B. Chester, Jordan W. Crowell, David W. Krause & Tyler R. Lyson (2026)
Southernmost occurrence of Purgatorius sheds light on the biogeographic history and diversification of the earliest primate relatives
Journal of Vertebrate Paleontology e2614024
doi: https://doi.org/10.1080/02724634.2026.2614024
https://www.tandfonline.com/doi/full/10.1080/02724634.2026.2614024
Free pdf:
https://www.tandfonline.com/doi/epdf/10.1080/02724634.2026.2614024
Fossils of the earliest known euarchontan mammals, purgatoriid plesiadapiforms, first appear during the aftermath of the Cretaceous/Paleogene mass extinction. The oldest and most basally branching plesiadapiform, Purgatorius, has been documented in Montana and Saskatchewan during the earliest Paleocene Puercan North American Land Mammal Age, but no plesiadapiforms have been recovered from southern basins of the Western Interior until later in the Paleocene. This temporal and geographic gap has made the early biogeographic history and diversification patterns of plesiadapiforms unclear. Here we report Purgatorius fossils recovered from extensive screen-washing of sediments from the Corral Bluffs study area, Denver Basin, Colorado, which represent the first Puercan occurrence of a plesiadapiform south of Montana. Isolated teeth of Purgatorius described here exhibit a unique combination of features, and may represent a new, early diverging species. This discovery bridges the temporal and geographic gap among the earliest plesiadapiforms and suggests a northern origin followed by a southerly diversification in the earliest Paleocene. The presumed absence of Puercan plesiadapiforms in southern regions of the Western Interior of North America was at least in part due to sampling biases. Additional screen-washing efforts in these regions will further clarify biogeographic patterns of plesiadapiforms and other small-bodied earliest Paleocene mammals.
====
Not yet mentioned:
Free pdf:
Charles J. Salcido & P. David Polly (2026)
Parallelism of mandibular function in therian carnivores: a morphometric, phylogenetic, and finite element analysis
Paleobiology 52(1): 104 - 120
DOI: https://doi.org/10.1017/pab.2025.10068
https://www.cambridge.org/core/journals/paleobiology/article/parallelism-of-mandibular-function-in-therian-carnivores-a-morphometric-phylogenetic-and-finite-element-analysis/5775F2C350A864CE3C324D882D64EFD5
The evolution of the mandible in mammalian carnivores is influenced by ecological demands that have changed over their phylogenetic history. We combined geometric morphometrics and biomechanical analysis (including beam analysis and finite element analysis, or FEA) to assess the interaction between form and function as the mandible has adapted independently to carnivorous diets in therian clades including Metatheria, Mesonychia, “Creodonta,” and Carnivoramorpha. Our goal was to determine the relative contributions of mechanical advantage, mandibular force, and mandibular resistance to bending and torsion, to the evolution of mandibular shape in these groups, as well as whether they produce differential rates of shape evolution in the horizontal and ascending rami, which respectively are the tooth-bearing and muscle-loading parts of the structure.
We found that the ascending ramus has higher rates of evolution than the horizontal ramus, making it the more rapidly evolvable portion of the mandible. Statistical evaluation supports this interpretation, as mechanical advantage and resistance to force explain more of the variance in shape than do the beam mechanic estimates that are heavily influenced by the mandibular body. Regression analysis shows that the evolution of specialized carnivory was associated with stronger mandibles in which mandibular shape changed by shortening and thickening of the mandible, increasing the areas of muscle attachment, and increasing the carnassial blade length. Principal component analysis of mandibular shape shows that different clades in Theria have been able to fill out similar specialized carnivorous niches with similar functional metrics despite having different mandibular morphologies.
=====
Reply all
Reply to author
Forward
0 new messages