The Phylogeny, Functional Anatomy, and Paleobiogeography of the Placodontia (Reptilia: Sauropterygia)

齿龙是一群爬行动物，在大约2.5亿年前入侵了中生代的海洋。齿齿类动物仅限于特提斯西部的动物区系。今天在中欧和地中海沿岸国家发现了它们的化石。牙齿兽的首次出现与下三叠纪海平面上升有关，海平面上升创造了栖息地，这一群体最终实现了多样化。这个群体在晚三叠纪海平面下降之后灭绝了。虽然以前已经发现了两个不同的齿形动物群体，“无甲”（placodonto总科）和“有甲”（cyamdonto总科），但这两个群体之间的关系仍然知之甚少。对齿形动物历史的进一步了解可能对理解爬行动物之间的整体关系具有重要意义。它也将提供必要的背景，以提高洞察力的功能解剖喂养系统的成员之间的群体。了解牙齿动物之间的历史生物地理关系，将反过来提高对它们所居住地区复杂地质历史的理解。

9815235 Rieppel The Placodontia were a group of reptiles that invaded the oceans of the Mesozoic around 250 million years ago. Placodonts were restricted to the western Tethyan faunal province. Their fossils are found today in Central Europe and circum-mediterranean countries. The first appearance of placodonts is correlated with a Lower Triassic sea-level rise that created the habitats where the group eventually diversified. The group went extinct in the aftermath of a Late Triassic drop in sea level. Although two separate groups of placodonts have previously been recognized, the "unarmored" (Placodontoidea) and the "armored" (Cyamdontoidea) placodonts, the relationships within the groups remain poorly understood. An improved understanding of the history of placodonts may have important consequences for understanding higher level relationships among reptiles as a whole. It will also provide the necessary background for improved insight on the functional anatomy of the feeding system among members of the group. Understanding the historical biogeographic relationships among placodonts will in turn improve understanding of the complex geological history of the region they inhabited.