Origin and early diversification of Plesiosauria and the influence of the end-Triassic extinction event: insights from the first unequivocal Triassic plesiosaurs

蛇颈龙类的起源和早期多样化以及三叠纪末灭绝事件的影响：来自第一批明确的三叠纪蛇颈龙的见解

基本信息

批准号：
286830904
负责人：
Professor Dr. Martin Sander
金额：
--
依托单位：
Lamont-Doherty Earth Observatory
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2020-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/286830904?language=en
关键词：
Origin early diversification Plesiosauria influence

项目摘要

Together with ichthyosaurs, plesiosaurs are the quintessential marine reptiles of the Age of Dinosaurs. Plesiosaurs belong to the clade Sauropterygia together with the exclusively Triassic placodonts, nothosaurs, and pistosaurs. Plesiosaurs are unique in that the forelimbs and hind limbs are of equal shape and were used in a four-winged underwater flight. The plesiosaur body is short and broad, and the primitive forms as well as the plesiosaurs proper have a very long neck with a small head. Plesiosaur origins are poorly understood because of the paucity of Late Triassic marine reptile localities and the lack of well-preserved intermediate forms between pistosaurs and plesiosaurs. Hitherto, plesiosaurs were exclusively known from the Jurassic and Cretaceous, with the oldest representatives from the earliest Jurassic of England. These are generally small-bodied forms, not exceeding 2 m in length. This project focusses on the first Triassic plesiosaur skeleton, a new find including skull remains and teeth, from the Rhaetian of eastern Westphalia, Germany, and on abundant isolated putative plesiosaur remains from Rhaetian bonebeds of Germany (also new finds) and England. The neck vertebrae of early plesiosaurs commonly show a complex v-shaped neurocentral suture which may be linked to a stiffening of the neck during underwater flight while allowing continued growth. With the new evidence of a Triassic origin of plesiosaurs, nothing argues agains assignment of the Rhaetian isolated bones and teeth to Plesiosauria. The specimens inform us about the early diversification of the group because of their great size and shape disparity, with some bones recording animals exceeding 5 m in length! This suggests that plesiosaurs reacted to the end-Triassic extinction event by size reduction but not by diversity reduction. Specifically, the proposed project will describe the new (and only) Triassic plesiosaur skeleton, analyze its phylogenetic position, describe the isolated Rhaetian plesiosaur bones, analyze their phylogenetic position among sauropterygians, study early plesiosaur tooth enamel microstructure, analyze the biomechanics of the basal plesiosaur neck in the context of the v-shaped neurocentral suture, and analyze morphological and size disparity among Triassic plesiosaurs, comparing it with the Early Jurassic record. The comparison with the closest plesiosaur relatives, Pistosauridae and Bobosaurus, will lead to a refined understanding of plesiosaur origins, the influence of the end-Triassic extinction event on their evolution, and the evolution of their unique mode of locomotion.

蛇颈龙与鱼龙一起，是恐龙时代典型的海洋爬行动物。蛇颈龙类与三叠纪独有的板齿龙类、蛇龙类和枪龙类一起属于蜥翼类分支。蛇颈龙的独特之处在于前肢和后肢形状相同，并用于四翼水下飞行。蛇颈龙的身体短而宽，原始形态以及蛇颈龙本身都有一个很长的脖子和一个小头。由于晚三叠世海洋爬行动物产地稀少，而且缺乏保存完好的蛇颈龙和蛇颈龙之间的中间形态，人们对蛇颈龙的起源知之甚少。迄今为止，蛇颈龙类仅存在于侏罗纪和白垩纪，其中最古老的代表来自英格兰最早的侏罗纪。这些通常是小型体型，长度不超过2 m。该项目的重点是来自德国威斯特伐利亚东部雷蒂亚的第一具三叠纪蛇颈龙骨架，这是一项新发现，包括头骨遗骸和牙齿，以及来自德国（也是新发现）和英国雷蒂亚骨床的大量孤立的推定蛇颈龙遗骸。早期蛇颈龙的颈椎通常呈现出复杂的V形神经中枢缝合线，这可能与水下飞行期间颈部变硬同时允许持续生长有关。有了蛇颈龙起源于三叠纪的新证据，没有什么理由反对将雷蒂亚孤立的骨骼和牙齿归属于蛇颈龙类。这些标本告诉我们该群体的早期多样化，因为它们的体型和形状差异巨大，一些骨头记录了动物的长度超过 5 m！这表明蛇颈龙对三叠纪末灭绝事件的反应是体型减小，而不是多样性减少。具体来说，该项目将描述新的（也是唯一的）三叠纪蛇颈龙骨骼，分析其系统发育位置，描述分离的雷蒂亚蛇颈龙骨骼，分析它们在蜥龙类中的系统发育位置，研究早期蛇颈龙牙釉质微观结构，分析基础蛇颈龙的生物力学颈部在 V 形神经中枢缝合的背景下，并分析形态和大小差异三叠纪蛇颈龙，与早侏罗世记录进行比较。通过与蛇颈龙最近亲——蛇颈龙科和博龙的比较，将有助于更好地了解蛇颈龙的起源、三叠纪末灭绝事件对其进化的影响，以及其独特运动方式的进化。