Klein Nicole, Furrer Heinz, Ehrbar Iris, Torres Ladeira Marta, Richter Henning, Scheyer Torsten M
Palaeontological Institute and Museum, University of Zurich, Karl Schmid-Strasse 4, CH-8006 Zurich, Switzerland.
Diagnostic Imaging Research Unit (DIRU), Clinic for Diagnostic Imaging, Department of Clinical Diagnostics and Services, Vetsuisse Faculty, University of Zurich, Winterthurerstrasse 258c, CH-8057 Zurich, Switzerland.
Swiss J Palaeontol. 2022;141(1):12. doi: 10.1186/s13358-022-00254-2. Epub 2022 Jul 13.
The Alpine Prosanto Formation (Middle Triassic) cropping out in the Ducan region in eastern Switzerland has yielded a rich fish and reptile fauna. Here, we present new pachypleurosaur remains from the upper part of the formation (Early Ladinian), similar to the previously known pachypleurosaurs from the Middle Triassic UNESCO World Heritage Site of Monte San Giorgio in southern Switzerland/northern Italy. From these remains, a new pachypleurosaur species, nov. gen. et spec., is described on the basis of six fairly complete skeletons, one disarticulated specimen and an isolated skull. As is typical for pachypleurosaurs and most other Triassic marine reptiles, the new taxon is based to a large degree on a combination of characters (e.g., nasals articulating broadly with the anterior margins of the prefrontals and lacking posterior processes; postorbitals with rounded anterior processes that articulate with the postfrontals anterolaterally) rather than on many unambiguous autapomorphies, although a few of the latter were found including (1) a premaxilla which is excluded from entering both the external and internal nares and (2) a parietal, which is distinctly longer than wide and carrying distinct anterolaterally angled processes. Phylogenetic relationships of the new taxon are tested within European Pachypleurosauria, revealing that the new species is the sister taxon to a clade including , , and the monophyletic spp. Mapping of palaeogeographic and stratigraphical distribution of valid European pachypleurosaurs shows that a formerly proposed scenario of migration of pachypleurosaurs from the eastern Palaeotethys during the Olenekian into the Germanic Basin and a subsequent diversification and invasion during the Anisian into the intraplatform basins of the South Alpine realm must be re-assessed. The exceptional preservation and preparation of the Ducan fossils further allow the description of tooth replacement patterns for the first time in a European pachypleurosaur species. The "alveolarization" of replacement teeth, the horizontal replacement pattern, and the subsequent remodelling of the functional alveoli during tooth replacement supports the monophyly of Sauropterygia as discussed before.
The online version contains supplementary material available at 10.1186/s13358-022-00254-2.
出露于瑞士东部杜坎地区的阿尔卑斯普罗桑托组（中三叠世）产出了丰富的鱼类和爬行动物化石群。在此，我们展示了该组上部（早拉丁期）新发现的肿肋龙化石，它们与之前在瑞士南部/意大利北部的中三叠世联合国教科文组织世界遗产地圣乔治山发现的肿肋龙相似。基于六具相当完整的骨骼、一个零散的标本和一个孤立的头骨，描述了一个新的肿肋龙物种，新属新种。与肿肋龙和大多数其他三叠纪海洋爬行动物一样，新分类单元在很大程度上基于多种特征的组合（例如，鼻骨与额骨前缘广泛相连且无后突；眶后骨的前突呈圆形，与额骨后外侧相连），而非许多明确的自近裔性状，不过也发现了一些后者，包括（1）一块不参与构成外鼻孔和内鼻孔的前上颌骨，以及（2）一块明显长大于宽且带有明显前外侧角状突的顶骨。在欧洲肿肋龙类中检验了新分类单元的系统发育关系，结果表明新物种是一个包括[具体物种1]、[具体物种2]和单系的[具体物种3]属物种的分支的姐妹分类单元。对欧洲有效肿肋龙的古地理和地层分布进行绘图显示，之前提出的肿肋龙在奥伦尼克期从东古特提斯迁移到日耳曼盆地，随后在安尼西期多样化并侵入南阿尔卑斯地区的陆内盆地的假说必须重新评估。杜坎化石的特殊保存和处理情况还首次使得能够描述欧洲肿肋龙物种的牙齿替换模式。替换牙的“牙槽化”、水平替换模式以及牙齿替换过程中功能性牙槽随后的重塑，支持了之前讨论过的鳍龙超目的单系性。
在线版本包含可在10.1186/s13358 - 022 - 00254 - 2获取的补充材料。
