The three-dimensionally articulated oral apparatus of a Devonian heterostracan sheds light on feeding in Palaeozoic jawless fishes

Attempts to explain the origin and diversification of vertebrates have commonly invoked the evolution of feeding ecology, contrasting the passive suspension feeding of invertebrate chordates and larval lampreys with active predation in living jawed vertebrates. Of the extinct jawless vertebrates that phylogenetically intercalate these living groups, the feeding apparatus is well-preserved only in the early diverging stem-gnathostome heterostracans. However its anatomy remains poorly understood. Here we use X-ray microtomography to characterise the feeding apparatus of the pteraspid heterostracan Rhinopteraspis dunensis (Roemer, 1855). The apparatus is composed of thirteen plates arranged approximately bilaterally, most of which articulate from the postoral plate. Our reconstruction shows that the oral plates were capable of rotating around the transverse axis, but likely with limited movement. It also suggests the nasohypophyseal organs opened internally, into the pharynx. The functiona..., Rhinopteraspis dunensis NHMUK PV P 73217 was scanned using a Nikon Metrology XTH 225ST X-ray tomography instrument based in Bristol Palaeobiology, University of Bristol. Two scans were undertaken, each composed of two stacked scans. The first scan included the whole headshield at a voltage of 223 kV and a current of 193 μA, with 3141 projections, and with a 1 mm Sn filter, obtaining a dataset with 63.41 μm voxel resolution. The second scan targeted the oral region specifically, including the posterior third of the rostrum, the orbital, oral, and pineal parts of the headshield, and the anterior quarter of the dorsal and ventral discs, at a voltage of 180 kV and a current of 178 μA, with 3141 projections of 8 frames and 708 ms each, and with a 0.5 mm Cu filter, achieving a voxel resolution of 22.91 μm.The resulting tomographic datasets were segmented in Mimics v.25 (materialise) to create 3D models. , , # The three-dimensionally articulated oral apparatus of a Devonian heterostracan sheds light on feeding in Palaeozoic jawless fishes This dataset contains supplementary data associated with Dearden *et al.* 2024 *Proceedings of the Royal Society B: Biological Sciences*. This data takes the form of two sets of 3D surface models derived from CT scans of the Palaeozoic jawless fish *Rhinopteraspis dunensis* NHMUK PV P 73217. ## Description of the data and file structure The data is provided in two zipped folders, each of which corresponds to one scan set. The details of these scans are provided in the related Open Access paper. The first folder \"Rhinopteraspis_High_Resolution\" comprises the 3D models derived from a higher resolution CT scan of the oral region of NHMUK PV P 73217. The second folder \"Rhinopteraspis_Low_Resolution\" comprises additional 3D models derived from CT scans of the entire specimen of NHMUK PV P 73217 including all plates not fully captured in the above scan. ...长期以来，阐释脊椎动物起源与演化辐射的研究通常援引进食生态的演化，将无脊椎脊索动物与七鳃鳗幼体的被动悬浮摄食，与现生有颌脊椎动物的主动捕食行为进行对比。在系统发育上介于这两类现生类群之间的已灭绝无颌脊椎动物中，进食器官仅在早期分化的干群有颌类异甲鱼类（Heterostraci）中保存完好，但其解剖结构仍鲜有深入认知。本研究借助X射线显微断层扫描（X-ray microtomography）技术，对鳍甲鱼形异甲鱼类杜氏菱鳞甲鱼（Rhinopteraspis dunensis, Roemer, 1855）的进食器官开展形态学解析。该进食器官由约呈双侧对称排布的13块骨板构成，其中多数骨板均与口后板相关节。重建结果显示，口部骨板可围绕横轴转动，但活动范围或较为有限。研究同时表明，鼻垂体器官向内开口于咽腔。[原文此处文本截断] 杜氏菱鳞甲鱼NHMUK PV P 73217的扫描工作由英国布里斯托大学布里斯托古生物学实验室的尼康Metrology XTH 225ST X射线断层扫描设备完成。本次扫描分为两组：第一组为两次叠加扫描的全头甲扫描，扫描参数为电压223 kV、电流193 μA，采集3141幅投影，使用1 mm锡滤片，所得数据集的体素分辨率为63.41 μm。第二组为针对性扫描口部区域，包含吻部后三分之一、头甲的眶部、口部及松果体区域，以及背甲与腹甲的前四分之一部分，扫描参数为电压180 kV、电流178 μA，采集3141幅投影，每幅投影曝光8帧、单帧曝光时长708 ms，使用0.5 mm铜滤片，最终体素分辨率为22.91 μm。所得断层扫描数据集通过Materialise Mimics v.25软件进行分割，以构建三维模型。 # 泥盆纪异甲鱼类三维铰接式进食器官揭示古生代无颌鱼类的摄食机制 本数据集关联Dearden等人2024年发表于《英国皇家学会学报B：生物科学》的研究成果。该数据集包含两套三维表面模型，均由古生代无颌鱼类杜氏菱鳞甲鱼NHMUK PV P 73217的CT扫描数据重建得到。 ## 数据与文件结构说明 本数据集以两个压缩文件夹的形式提供，分别对应两组扫描序列，扫描细节详见相关开放获取论文。 第一个文件夹"Rhinopteraspis_High_Resolution"包含由NHMUK PV P 73217口部区域的高分辨率CT扫描数据重建得到的三维模型。 第二个文件夹"Rhinopteraspis_Low_Resolution"包含由NHMUK PV P 73217全标本的CT扫描数据重建得到的补充三维模型，涵盖了前述高分辨率扫描未完全捕捉的所有骨板。