Dearden Richard P, Johanson Zerina, O'Neill Helen L, Miles Kieran, Bernard Emma L, Clark Brett, Underwood Charlie J, Rücklin Martin
Vertebrate Evolution, Development, and Ecology, Naturalis Biodiversity Center, Leiden 2333 CR, The Netherlands.
School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK.
R Soc Open Sci. 2025 Apr 30;12(4):242011. doi: 10.1098/rsos.242011. eCollection 2025 Apr.
A rich fossil record of teeth shows that many living shark families' origins lie deep in the Mesozoic. Skeletal fossils of the sharks to whom these teeth belonged are far rarer and when they are preserved are often flattened, hindering understanding of the evolutionary radiation of living shark groups. Here we use computed tomography to describe two articulated Upper Cretaceous shark skeletons from the Chalk of the UK preserving three-dimensional neurocrania, visceral cartilages, pectoral skeletons and vertebrae. These fossils display skeletal anatomies characteristic of the Parascylliidae, a family of Orectolobiformes now endemic to Australia and the Indo Pacific. However, they differ in having a more heavily mineralized braincase and a tri-basal pectoral fin endoskeleton, while their teeth can be attributed to a new species of the problematic taxon . Phylogenetic analysis of these new fossils confirms that is a stem-group parascylliid, providing insight into the evolution of parascylliids' distinctive anatomy during the late Mesozoic-Cenozoic shift in orectolobiform biodiversity from the Northern Atlantic to the Indo Pacific. Meanwhile both and extant parascylliids have a distinctive vertebral morphology previously described only in Carcharhiniformes, contributing a skeletal perspective to the picture emerging from macroevolutionary analyses of coastal, small-bodied origins for galeomorphs.
丰富的牙齿化石记录表明，许多现存鲨鱼家族的起源可追溯到中生代深处。这些牙齿所属鲨鱼的骨骼化石则极为罕见，即便保存下来也往往已被压扁，这阻碍了我们对现存鲨鱼群体进化辐射的理解。在此，我们利用计算机断层扫描技术，描述了来自英国白垩纪的两具铰接式上白垩统鲨鱼骨骼，这些骨骼保留了三维的脑颅、内脏软骨、胸鳍骨骼和脊椎。这些化石展现出了须鲨科的骨骼解剖特征，须鲨科是须鲨目的一个家族，如今仅分布于澳大利亚和印度太平洋地区。然而，它们有所不同，其脑壳矿化程度更高，胸鳍内骨骼具有三基底结构，同时它们的牙齿可归属于一个有问题分类单元的新物种。对这些新化石的系统发育分析证实，[物种名称]是须鲨科的干群成员，这为研究须鲨科独特解剖结构在中生代晚期至新生代期间须鲨目生物多样性从北大西洋向印度太平洋转变过程中的演化提供了见解。与此同时，[物种名称]和现存的须鲨科成员都具有一种独特的脊椎形态，这种形态此前仅在真鲨目中有描述，这为从宏观进化分析中得出的关于真鲨目沿海小型起源的图景提供了骨骼方面的视角。
