Limb histology of the Triassic stem turtles Proterochersis porebensis (Testudinata, Proterochersidae) and Proganochelys quenstedtii (Testudinata, Proganochelyidae)
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ID: 000532724
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Data on turtle limb bone histology and microstructure are spotty, especially for fossil taxa, despite significant progress made in recent years. Here we provide first detailed information on stylopodia of Late Triassic stem turtles: Proganochelys quenstedtii from Switzerland and Proterochersis porebensis from Poland. In both taxa we observed large, internal medullary regions filled with endosteal trabeculae and poorly to moderately vascularized parallel-fibered (grading locally to lamellar) periosteal cortices. Primary vasculature is predominantly longitudinal, in Proterochersis porebensis locally with radial inclination. In large specimens, secondary remodeling is significant in the deeper cortex, but in neither specimen it completely obliterates the primary tissue or reaches the external surface of the bone. Overall, the histological and microstructural characteristics of stylopodial bones of Triassic turtles resemble more those of derived representatives of that group than earlier Pantestudinata.