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[dinosaur] Coahomasuchus (Aetosauria) growth pattern + Nanhsiungchelys revised




Ben Creisler
bcreisler@gmail.com


Recent non-dino papers:


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Devin K. Hoffman, Andrew B. Heckert & Lindsay E. Zanno (2018)
Disparate growth strategies within Aetosauria: Novel Histologic Data from the aetosaur Coahomasuchus chathamensis.
The Anatomical Record (advance online publication)
doi:Â https://doi.org/10.1002/ar.24019
https://onlinelibrary.wiley.com/doi/10.1002/ar.24019



Aetosaurs comprise a clade of quadrupedal, armored, omnivores to herbivores that lived across much of the supercontinent of Pangea during the Late Triassic. Their relative abundance in many units, and the rarity of other Triassic herbivores, points to them as key components of Late Triassic ecosystems. Debate persists about whether they were growing more or less slowly when compared to extant crocodylians, and bone histology is sparsely sampled within the group. We undertook a histological examination of Coahomasuchus chathamensis in order to address its ontogenetic trajectory and characterize its histology. We sampled a paramedian osteoderm from the holotype specimen, as well as five osteoderms (two paramedian, one lateral, and two of uncertain position) and two incomplete limb bones (radius and fibula), from referred specimens discovered at the type locality. Using these we estimated specimen ages with lines of arrested growth (LAGs) to determine that the study individuals reached from two to seven years old. All of the sampled elements contained wovenâfibered bone with extensive vasculature within the internal cortex. In some specimens, more poorly vascularized, parallelâfibered bone is evident externally. The holotype of C. chathamensis represents a juvenile individual, and raises the possibility that the holotype of C. kahleorum is a juvenile as well, complicating aetosaur systematics and diversity. When compared to aetosaurs of similar size, it is clear that C. chathamensis was growing comparatively rapidly, about three times the rate of similarly sized specimens of Aetosauroides scagliai from Argentina. This discovery reveals the presence of disparate growth strategies within Aetosauria.

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Haiyan Tong & Lu Li (2018)
A revision of the holotype of Nanhsiungchelys wuchingensis, Ye, 1966 (Testudines: Cryptodira: Trionychoidae: Nanhsiungchelyidae).
Cretaceous Research (advance online publication)
doi: https://doi.org/10.1016/j.cretres.2018.11.003Â
https://www.sciencedirect.com/science/article/pii/S0195667118301745



Nanhsiungchelys wuchingensisYe, 1966 is the type genus and species of the family Nanhsiungchelyidae (Testudines: Cryptodira: Trionychoidae) known from the Cretaceous continental deposits of Asia and North America. The holotype of this species (IVPP V 3106), a partial skeleton from the uppermost Cretaceous of Nanxiong Basin, southern China, represents one of the most complete specimens of that family. Our revision provides new insights on the skeletal morphology. The structure of the forelimb supports a terrestrial mode of life. The phylogenetic relationships are discussed and the more precise stratigraphical information is provided.


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