Section Paleontology, Institute of Geosciences, University of Bonn, Bonn, Germany.
Dinosaur Institute, Natural History Museum of Los Angeles County, Los Angeles, California, USA.
Anat Rec (Hoboken). 2021 Mar;304(3):570-583. doi: 10.1002/ar.24468. Epub 2020 Jun 21.
Here we describe the histology and microanatomy of vertebral centra of the iconic pelycosaur-grade 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 50-80 μm of the vertebrae in the sagittal and transversal cutting planes. After the preparation process, the thin sections were examined under transmitted and cross-polarized light in a polarized microscope. The analyzed vertebrae reveal similar bone tissues, where both taxa have cortical parallel-fibered bone (PFB). PFB and lamellar bone (LB) forms in the cancellous part. However, in juvenile Dimetrodon, woven-fibered 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 of Dimetrodon 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 Dimetrodon vertebral centra 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 habitat.
在这里，我们描述了标志性的合弓类盘龙目爬行动物埃德弗龙属和异齿龙属的椎体的组织学和微观解剖结构。选择了来自不同轴向位置的椎体，对于异齿龙，还选择了来自不同个体发育阶段的椎体。为了进行组织学描述，我们在矢状面和横断面切面上对椎体进行了 50-80μm 厚的组织学岩相薄片的研磨。在准备过程之后，将薄片在偏光显微镜下用透射光和正交偏光进行检查。分析的椎体显示出相似的骨骼组织，其中两个分类群都具有皮质平行纤维骨（PFB）。PFB 和板层骨（LB）在松质骨部分形成。然而，在幼年异齿龙中，编织纤维骨（WFB）也被沉积，并且显示出高度的血管化。这表明异齿龙的骨骼生长速度略高于埃德弗龙，后者主要由 PFB 和 LB 组成，并且显示出发育不良的血管通道。此外，一个异齿龙标本显示出骨化脊索的保存，可以假定这表明了椎间组织的发育方式。从历史上看，直到这个标本出现之前，都缺乏关于异齿龙椎体中心之间的关节是如何构建的证据。如果脊索持续贯穿椎体，它可能会增加脊柱的刚度，并会影响四肢和运动。此外，小梁的组织和椎体皮质的相对厚度提供了有关动物如何适应其栖息地的见解。
