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Peirosaurid crocodylomorph bone histology and life history + Mesosaurus tail + Triceratops skeleton bioerosion

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Ben Creisler

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Jan 23, 2025, 2:06:02 PMJan 23
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Ben Creisler

Some recent papers:

Tamara G. Navarro, Ignacio A. Cerda, Leonardo S. Filippi & Diego Pol (2025)
Life history and growth dynamics of a peirosaurid crocodylomorph (Mesoeucrocodylia; Notosuchia) from the Late Cretaceous of Argentina inferred from its bone histology
Journal of Anatomy (advance online publication)
doi: https://doi.org/10.1111/joa.14182
https://onlinelibrary.wiley.com/doi/10.1111/joa.14182


Notosuchia were a successful lineage of Crocodyliformes that achieved a remarkable diversity during the Cretaceous of Gondwana, particularly in South America. Although paleohistology has expanded our knowledge of the paleobiology of notosuchians, several clades of this lineage remain poorly understood in this aspect. Here we help to address this gap by conducting the first histological analysis of appendicular bones of a peirosaurid. To increase our knowledge about growth dynamics and examine intraskeletal and interspecific histological variation, we analyze the microstructure of a tibia, fibula, phalanx, fragment of ornamented element (possible osteoderm or skull bone) and a possible long bone of an individual assigned to Peirosauridae indet. (MAU-Pv-437). The peirosaurid studied here appears to have reached sexual but not somatic maturity and the minimum age inferred from appendicular bones results in a lower estimated than the age inferred from osteoderms in a previous study on the same individual. The cortical bone in MAU-Pv 437 is formed by vascularized parallel fibered bone/lamellar bone which indicates that this individual experienced a moderate growth rate. This indicates different growth dynamics from what has been observed for other notosuchians specimens, suggesting a lack of a uniform growth pattern for this clade.

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Free pdf:

Graciela PIÑEIRO, Jorge FERIGOLO, Brodsky Dantas Macedo de FARIAS, Pablo NÚÑEZ DEMARCO & Michel LAURIN (2025)
Caudal autotomy in Mesosaurus tenuidens Gervais, 1865 under scrutiny and a surprising new pattern of vertebral organization in the mesosaur tail.
Geodiversitas 47(2): 17-38
doi: https://doi.org/10.5252/geodiversitas2025v47a2
https://sciencepress.mnhn.fr/en/periodiques/geodiversitas/47/2

Free pdf:
https://sciencepress.mnhn.fr/sites/default/files/articles/hd/geodiversitas2025v47a2-pdfa.pdf
  


Mesosaurs are basal amniotes that lived in an extended epicontinental sea resulting from Devonian and Carboniferous glaciations reported in Southern Gondwana. Previously considered to be marine animals, this interpretation is not supported by their skeletal anatomy, and was updated to a more semiaquatic style, prompting increased interest for mesosaur studies. Recently, transverse fractures and weak ossified areas at the subcentral surface of some caudal vertebrae have been interpreted as fracture planes related to a putative capability of autotomy in mesosaurs. We reassess the data used in support of caudal autotomy and identify the constraining morphological features of the involved vertebrae that contradict the development of such ability in mesosaurs. Moreover, we analyze the physiological and behavioral negative consequences that the loss of part of the tail would represent for aquatic and semiaquatic animals. The fact that no extant taxa living in these environments developed caudal autotomy supports our interpretations. We present an alternative hypothesis that suggests the presence of multipartite caudal centra represented by pleurocentrum and intercentrum arranged in the way expected for a reverse embolomerous pattern, previously undescribed for early stegocephalians or amniotes. However, a rapid revision of specialized literature suggests that the pattern could have been present in other basal amniotes and the possibility deserves additional studies, mainly in juvenile individuals. Our reinterpretation of the structure of mesosaur caudal vertebrae supports the proposed morphological plasticity observed in many clades of basal stegocephalians and amniotes and would match the recently suggested phylogenetic affinities of mesosaurs with respect to taxa that are close to, or part of the amniote stem under some phylogenies.


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Jack R. Milligan, Emily L. Bamforth, M. Gabriela Mángano & Luis A. Buatois (2025)
Taphonomic history of a dinosaur skeleton from the upper Cretaceous Frenchman Formation, Canada: insights from ancient rhizoetchings and invertebrate bioerosion trace fossils
Ichnos (advance online publication)
doi: https://doi.org/10.1080/10420940.2025.2449656
https://www.tandfonline.com/doi/full/10.1080/10420940.2025.2449656


Bioerosion trace fossils are biogenic structures that record evidence of behaviour in hard substrates, including bone. While bioerosion trace fossils on bones produced by animals have been well documented globally throughout the Mesozoic and Cenozoic, studies on such structures created by ancient plants are less common. Herein, we document an incomplete Triceratops skeleton from the latest Maastrichtian Frenchman Formation in southwestern Saskatchewan, Canada, which features several bioerosion trace fossils. The quarry containing the specimen consists of a blocky white to pink organic-rich mudstone, with a dense system of fossil root structures surrounding the bone material. This mudstone is interpreted as a heavily vegetated floodplain paleosol. Fossilized plant material associated with the Triceratops bones is preserved as compressed, black carbonaceous root structures lying within shallow horizontal furrows penetrating the cortical surface of the bone (i.e. rhizoetchings). Additional trace fossils include Amphifaoichnus seilacheri and Cubiculum inornatus, which are thought to have been produced by insects. This study contributes to our understanding of the taphonomic processes that affect Cretaceous vertebrate deposits and may elucidate the previously unappreciated role ancient plants played in the preservation and taphonomy of dinosaur skeletons.
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