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 Walcott, 1912 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 submillimeter-diameter raised nodes are described. These new features have not been observed in material from the Burgess Shale and suggest slight differences in preservation.

产自美国犹他州中寒武统（第3统）兰斯顿组（斯宾塞页岩段）、惠勒组与马朱姆组的放射齿类（Radiodonta）躯体构件已被报道，其中部分隶属于皮托虾属（Peytoia）与赫德虾属（Hurdia），另有部分暂未归入任何类群。本研究结合近年针对赫德虾属形态学的研究成果，对上述鉴定结论进行了重新厘定。此次在斯宾塞页岩中鉴定出赫德虾属的新标本，包括口锥、头甲H型骨片、前附肢以及一枚孤立的游泳叶。借助头甲H型骨片的形态特征，我们首次在斯宾塞页岩中确认了维多利亚赫德虾（H. victoria Walcott, 1912）的存在。该游泳叶的尺寸较布尔吉斯页岩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属游泳叶的形态结构。对赫德虾前附肢的三维模型分析表明，两个赫德虾物种中仅存在一种前附肢形态型，此前被认为是分离附肢间的表观形态差异，实则是因与海底呈不同斜角所导致的保存连续体差异。皮托虾属不应再被报道于斯宾塞页岩中，但该属确实存在于惠勒组与马朱姆组中。本次还描述了产自斯宾塞页岩的赫德虾属以及产自马朱姆组的皮托虾属的新型口锥，其表面具有亚毫米级凸起结节的纹理特征。这类新特征在布尔吉斯页岩的标本中尚未被观察到，暗示二者在保存过程中存在细微差异。