Macrospondylus (Jurassic teleosaur) paleohistology + Ostrombatrachos, new frog from Lower Cretaceous Cloverly Formation
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Ben Creisler
Sep 28, 2024, 2:46:58 PM (13 days ago) Sep 28
to DinosaurMa...@googlegroups.com
Ben Creisler
Free pdf:
https://anatomypubs.onlinelibrary.wiley.com/doi/epdf/10.1002/ar.25577
The Posidonienschiefer Formation of southern Germany has yielded an array of incredible fossil vertebrates. One of the best represented clades therein is Teleosauroidea, a successful thalattosuchian crocodylomorph group that dominated the coastlines. The most abundant teleosauroid, Macrospondylus bollensis, is known from a wide range of body sizes, making it an ideal taxon for histological and ontogenetic investigations. Previous studies examining thalattosuchian histology provide a basic understanding of bone microstructure in teleosauroids, but lack the taxonomic, stratigraphic, and ontogenetic control required to understand growth and palaeobiology within a species. Here, we examine the bone microstructure of three femora and one tibia from three different-sized M. bollensis individuals. We also perform bone compactness analyses to evaluate for ontogenetic and ecological variation. Our results suggests that (1) the smallest specimen was a young, skeletally immature individual with well-vascularized-parallel-fibered bone and limited remodeling in the midshaft periosteal cortex; (2) the intermediate specimen was skeletally immature at death, with vascularized parallel-fibered bone tissue interrupted by at least 10 LAGs, but no clear external fundamental system (EFS), and rather extensive inner cortical bone remodeling; and (3) the largest specimen was skeletally mature, with parallel-fibered bone tissue interrupted by numerous LAGs, a well-developed EFS, and extensive remodeling in the deep cortex. Macrospondylus bollensis grew relatively regularly until reaching adult size, and global bone compactness values fall within the range reported for modern crocodylians. The lifestyle inference models used suggest that M. bollensis was well adapted for an aquatic environment but also retained some ability to move on land. Finally, both larger specimens display a peculiar, localized area of disorganized bone tissue interpreted as pathological.
Recent papers not yet mentioned:
Free pdf:
Michela M. Johnson, Torsten M. Scheyer, Aurore Canoville & Erin E. Maxwell (2024)
Palaeohistology of Macrospondylus bollensis (Crocodylomorpha: Thalattosuchia: Teleosauroidea) from the Posidonienschiefer Formation (Toarcian) of Germany, with insights into life history and ecology
The Anatomical Record (advance online publication)
doi: https://doi.org/10.1002/ar.25577
https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25577
Michela M. Johnson, Torsten M. Scheyer, Aurore Canoville & Erin E. Maxwell (2024)
Palaeohistology of Macrospondylus bollensis (Crocodylomorpha: Thalattosuchia: Teleosauroidea) from the Posidonienschiefer Formation (Toarcian) of Germany, with insights into life history and ecology
The Anatomical Record (advance online publication)
doi: https://doi.org/10.1002/ar.25577
https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25577
Free pdf:
https://anatomypubs.onlinelibrary.wiley.com/doi/epdf/10.1002/ar.25577
The Posidonienschiefer Formation of southern Germany has yielded an array of incredible fossil vertebrates. One of the best represented clades therein is Teleosauroidea, a successful thalattosuchian crocodylomorph group that dominated the coastlines. The most abundant teleosauroid, Macrospondylus bollensis, is known from a wide range of body sizes, making it an ideal taxon for histological and ontogenetic investigations. Previous studies examining thalattosuchian histology provide a basic understanding of bone microstructure in teleosauroids, but lack the taxonomic, stratigraphic, and ontogenetic control required to understand growth and palaeobiology within a species. Here, we examine the bone microstructure of three femora and one tibia from three different-sized M. bollensis individuals. We also perform bone compactness analyses to evaluate for ontogenetic and ecological variation. Our results suggests that (1) the smallest specimen was a young, skeletally immature individual with well-vascularized-parallel-fibered bone and limited remodeling in the midshaft periosteal cortex; (2) the intermediate specimen was skeletally immature at death, with vascularized parallel-fibered bone tissue interrupted by at least 10 LAGs, but no clear external fundamental system (EFS), and rather extensive inner cortical bone remodeling; and (3) the largest specimen was skeletally mature, with parallel-fibered bone tissue interrupted by numerous LAGs, a well-developed EFS, and extensive remodeling in the deep cortex. Macrospondylus bollensis grew relatively regularly until reaching adult size, and global bone compactness values fall within the range reported for modern crocodylians. The lifestyle inference models used suggest that M. bollensis was well adapted for an aquatic environment but also retained some ability to move on land. Finally, both larger specimens display a peculiar, localized area of disorganized bone tissue interpreted as pathological.
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Ostrombatrachos nodos gen. et sp. nov.,
Matthew P. J. Oreska, David G. DeMar JR., James D. Gardner & Matthew T. Carrano (2024)
Vertebrate paleontology of the Cloverly Formation (Lower Cretaceous), IV: the oldest edentulous frog (Salientia) from Laurasia
Journal of Vertebrate Paleontology: e2399102
doi: https://doi.org/10.1080/02724634.2024.2399102
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2399102
Edentulism—lack of teeth—is a derived condition among salientians (total-group frogs and toads) that has arisen independently at least 22 times within the crown group, Anura. Despite this frequency, edentulism (in part or complete) is seldom documented in the salientian fossil record, and thus its evolutionary history remains obscure. A ∼90 Ma gap presently exists between the edentulous salientians Notobatrachus reigi (late Toarcian; Argentina) and the five known species from the latest Cretaceous of Argentina, South Africa, Canada, and the U.S.A. Here we report a new instance of edentulism in an Early Cretaceous salientian, Ostrombatrachos nodos gen. et sp. nov., based on a maxilla from an early Albian age (∼ 111 Ma) locality in the Cloverly Formation of Wyoming, U.S.A. Although incomplete, the holotype maxilla exhibits a distinctive suite of features (i.e., edentulous; pit-and-ridge external ornament; shallow groove across anteriormost portion of margo orbitalis and continuing anteroventrally down lateral surface of pars facialis to interrupt the external ornament; medially expanded orbital flange; moderately broad, deep lamina horizontalis; and weakly developed processus pterygoideus) that is unknown in any other salientian. This new taxon represents the oldest occurrence of edentulous maxillae in a Laurasian salientian and helps fill the long temporal gap in edentulism among salientians. O. nodos gen. et sp. nov. does not appear to be closely related to other edentulous Mesozoic salientians, suggesting it represents yet another independent evolution of this feature.
Matthew P. J. Oreska, David G. DeMar JR., James D. Gardner & Matthew T. Carrano (2024)
Vertebrate paleontology of the Cloverly Formation (Lower Cretaceous), IV: the oldest edentulous frog (Salientia) from Laurasia
Journal of Vertebrate Paleontology: e2399102
doi: https://doi.org/10.1080/02724634.2024.2399102
https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2399102
Edentulism—lack of teeth—is a derived condition among salientians (total-group frogs and toads) that has arisen independently at least 22 times within the crown group, Anura. Despite this frequency, edentulism (in part or complete) is seldom documented in the salientian fossil record, and thus its evolutionary history remains obscure. A ∼90 Ma gap presently exists between the edentulous salientians Notobatrachus reigi (late Toarcian; Argentina) and the five known species from the latest Cretaceous of Argentina, South Africa, Canada, and the U.S.A. Here we report a new instance of edentulism in an Early Cretaceous salientian, Ostrombatrachos nodos gen. et sp. nov., based on a maxilla from an early Albian age (∼ 111 Ma) locality in the Cloverly Formation of Wyoming, U.S.A. Although incomplete, the holotype maxilla exhibits a distinctive suite of features (i.e., edentulous; pit-and-ridge external ornament; shallow groove across anteriormost portion of margo orbitalis and continuing anteroventrally down lateral surface of pars facialis to interrupt the external ornament; medially expanded orbital flange; moderately broad, deep lamina horizontalis; and weakly developed processus pterygoideus) that is unknown in any other salientian. This new taxon represents the oldest occurrence of edentulous maxillae in a Laurasian salientian and helps fill the long temporal gap in edentulism among salientians. O. nodos gen. et sp. nov. does not appear to be closely related to other edentulous Mesozoic salientians, suggesting it represents yet another independent evolution of this feature.
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