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

9815235白齿龙是一群爬行动物，大约在2.5亿年前入侵了中生代的海洋。胎牙化石仅限于西部特提斯动物区系省。它们的化石今天在中欧和环地中海国家被发现。胎牙化石的首次出现与下三叠统海平面上升有关，这造就了该物种最终多样化的栖息地。在晚三叠世海平面下降之后，这个群体灭绝了。尽管先前已识别出两组不同的胎牙，即“无装甲”(Placodontoidae)和“装甲”(Cyamdontoidae)，但这两组之间的关系仍然知之甚少。更好地了解胎牙的历史可能会对整体理解爬行动物之间的更高级别的关系产生重要的影响。它还将提供必要的背景知识，以便在小组成员中更好地了解进食系统的功能解剖。了解地牙石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.