Data from: The skull and endocranium of a Lower Jurassic ichthyosaur based on digital reconstructions

Even after 200 years of study, some details of the cranial anatomy of ichthyosaurs, one of the most successful groups of marine vertebrates in the Mesozoic, are still unclear. New information on the braincase, palate and occiput are provided from three-dimensional scans of an exceptionally preserved ichthyosaur (‘Hauffiopteryx’ typicus) skull from the Toarcian (183–174 Ma, Lower Jurassic) of Strawberry Bank, England. This ichthyosaur has unusual, hollow, tubular hyoid bars. The occipital and braincase region is fully reconstructed, creating the first digital cranial endocast of an ichthyosaur. Enlarged optic lobes and an enlarged cerebellum suggest neuroanatomical adaptations that allowed it to be a highly mobile, visual predator. The olfactory region also appears to be enlarged, suggesting that olfaction was more important for ichthyosaurs than has been assumed. Phylogenetic analysis suggests this ichthyosaur is closely related to, but distinct from, Hauffiopteryx, and positioned within Thunnosauria, a more derived position than previously recovered. These results further our knowledge of ichthyosaur cranial anatomy in three dimensions and provide a platform in which to study the anatomical adaptations that allowed ichthyosaurs to dominate the marine realm during the Mesozoic尽管已历经二百余年的研究，中生代（Mesozoic）最成功的海洋脊椎动物类群之一的鱼龙（ichthyosaur），其颅部解剖学的诸多细节仍未完全明晰。本次研究通过对英国草莓滩（Strawberry Bank）下侏罗统托阿尔阶（Toarcian，183–174 Ma）中一件保存极为完好的鱼龙（‘Hauffiopteryx’ typicus）头骨开展三维扫描，获取了其脑颅（braincase）、腭部（palate）与枕区（occiput）的全新研究数据。该鱼龙拥有独特的中空管状舌骨杆（hyoid bar）。研究人员对其枕区与脑颅区域进行了完整重建，获得了首例鱼龙的数字化颅内腔模（cranial endocast）。其膨大的视叶（optic lobe）与小脑提示，该物种具备适配高度活跃的视觉捕食习性的神经解剖学适应性特征。其嗅觉区域同样呈现膨大状态，表明嗅觉在鱼龙的生存中所扮演的角色比此前所认为的更为重要。系统发育分析（phylogenetic analysis）显示，该鱼龙与霍夫鱼龙（Hauffiopteryx）亲缘关系密切但自成一类，且被归入金枪形鱼龙类（Thunnosauria），其演化位置比此前复原的更为衍化。本研究成果进一步完善了我们对鱼龙三维颅部解剖学的认知，并为探究鱼龙得以在中生代海洋中占据统治地位的解剖学适应性特征提供了研究基础。