Imaging a newly discovered giant fossil marine reptile flipper with extensive soft tissues and bone-like serrations

Ichthyosaurs were a highly successful group of ancient marine reptiles whose fossils have been studied for more than 200 years. Here we focus on a recently collected, ~1.2 m long, articulated forelimb with a virtually intact soft-tissue outline. This unique fossil includes the first known soft parts of Temnodontosaurus, a giant 10–12 m long apex predator of the Jurassic seas. The fossil illustrates – for the first time – and contrary to all other marine tetrapods (both extinct and extant ones), that the distal fin was unsupported by skeletal elements and that the trailing edge contained bony serrations embedded in the skin. We propose to combine two imaging techniques (using neutrons and X-rays) to better understand the distribution of the soft tissues, to identify important skeletal elements and to visualise the unique 3D dermal ossifications. The expected results will greatly assist in our understanding of the hunting behaviours of this enormous ichthyosaur and whether its unusual forelimb anatomy, combined with its gigantic eyes, helped it to rely on stealth while hunting under the cover of darkness using powerful night-vision.

鱼龙类（Ichthyosaurs）是一类极为成功的史前海洋爬行动物，其化石的研究历史已超过200年。本研究聚焦于一件新近采集的、长约1.2米的关联前肢化石，其软组织轮廓几乎完整保存。这件独特化石保存了泰曼鱼龙（Temnodontosaurus）已知的首例软组织残骸——泰曼鱼龙是一种体长10至12米的侏罗纪海洋顶级捕食者。该化石首次揭示了与所有其他海洋四足动物（无论已灭绝还是现生类群）截然不同的特征：其远端鳍部无骨骼支撑，且鳍的后缘带有嵌入皮肤的骨质锯齿状结构。我们计划结合中子与X射线两种成像技术，以更清晰地解析软组织分布、识别关键骨骼结构，并可视化这件化石独特的三维真皮骨化结构。预期研究结果将极大助力我们理解这类巨型鱼龙的捕猎行为，以及其非同寻常的前肢解剖结构与巨型眼部相结合，是否帮助它借助强大的夜视能力在黑暗掩护下依靠伏击进行捕猎。