Data from: Hurdiid radiodontans from the middle Cambrian (Series 3) of Utah

Radiodontan body elements, some belonging to Peytoia and Hurdia and some unassigned, have been reported from the Langston Formation (Spence Shale Member), Wheeler Formation, and Marjum Formation of the middle Cambrian (Series 3) of Utah. These identifications are reassessed in light of recent work on the morphology of the radiodontan Hurdia. New specimens of Hurdia are identified from the Spence Shale, representing mouthparts (oral cones), cephalic carapace H-elements, frontal appendages and a single isolated swimming flap. The shape of the H-elements allows H. victoria to be identified from the Spence Shale for the first time. The flap is larger and more complete than any reported from the Burgess Shale, and allows for a better understanding of the morphology of Hurdia swimming flaps. A 3D model of a Hurdia frontal appendage indicates that there is only one morph of Hurdia frontal appendage found in both species, and apparent morphological differences between disarticulated appendages reflect a preservational continuum caused by varying oblique angles relative to the seafloor. Peytoia should no longer be reported from the Spence Shale, but its presence is confirmed in the Wheeler and Marjum formations. New mouthparts (oral cones) of Hurdia from the Spence Shale and Peytoia from the Marjum Formation with surface textures of sub-millimeter diameter raised nodes are described. These new features have not been observed in material from the Burgess Shale, and suggest slight differences in preservation.

本次研究对产自美国犹他州中寒武统（第3统）兰斯顿组（Langston Formation）下属斯宾塞页岩段（Spence Shale Member）、惠勒组（Wheeler Formation）与马朱姆组（Marjum Formation）的放射齿类（radiodontan）躯体构件展开重新厘定，其中部分构件归属于皮托虾（Peytoia）与赫德虾（Hurdia），另有部分暂未指定类群。基于近年针对赫德虾形态学的研究进展，本次研究重新评估了此前的物种鉴定结果。研究在斯宾塞页岩中识别出赫德虾的新标本，包括口锥（oral cones）、头甲H型骨片（cephalic carapace H-elements）、前附肢（frontal appendages）以及一枚孤立的游泳叶（swimming flap）。通过头甲H型骨片的形态特征，本次研究首次在斯宾塞页岩中确认了维多利亚赫德虾（H. victoria）的存在。该游泳叶的尺寸较布尔吉斯页岩（Burgess Shale）中已报道的同类标本更大、保存更完整，有助于更深入地理解赫德虾游泳叶的形态结构。对赫德虾前附肢的三维模型分析显示，两种赫德虾中仅存在一种前附肢形态，此前看似存在差异的分离附肢形态，实则是因与海底的斜置角度不同而形成的保存连续体（preservational continuum）。斯宾塞页岩中不应再报道皮托虾的存在，但其在惠勒组与马朱姆组中的分布已得到证实。本次研究还描述了斯宾塞页岩中赫德虾以及马朱姆组中皮托虾的新型口锥，其表面具有亚毫米级直径的凸起节点纹理。这些新特征在布尔吉斯页岩的标本中未曾被观察到，暗示二者的保存方式存在细微差异。