A new paper:
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Here we describe the histology and microanatomy of vertebral centra of the iconic pelycosaurâgrade synapsids Edaphosaurus boanerges and Dimetrodon spp. Vertebrae from different axial positions and, in the case of Dimetrodon , from different ontogenetic stages were selected. For the histological description, we produced histological petrographic thin sections ground to a thickness of 50â80 Îm of the vertebrae in the sagittal and transversal cutting planes. After the preparation process, the thin sections were examined under transmitted and crossâpolarized light in a polarized microscope. The analyzed vertebrae reveal a similar deposit of bone tissue, where both taxa have cortical parallelâfibered bone (PFB). PFB and lamellar bone (LB) forms in the cancellous part. However, in juvenile Dimetrodon, wovenâfibered bone (WFB) is also deposited and shows a high degree of vascularity. This suggests that Dimetrodon had slightly faster bone growth than Edaphosaurus , which is mainly made of PFB and LB and shows poorly developed vascular canals. In addition, one specimen displays the preservation of an ossified notochord, which can be assumed to be indicative of how the intervertebral tissues were developed. Historically, evidence of how the joint between their vertebral centrum was built was lacking until this specimen appeared. If the notochord ran persistently through the vertebrae, it would have possibly increased the stiffness of the vertebral column and would have affected the limbs and locomotion. Furthermore, the organization of trabeculae and relative thickness of the vertebral cortex gives insights into how the animals were adapted to their biotope.
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