The last pteraspids (Agnatha, Heterostraci): New material from the Middle Devonian of Alberta and Idaho

This report documents the last pteraspids, (armored, jawless members of the Heterostraci), which are otherwise only known from the Early Devonian of the Old Red Sandstone Continent. Tuberculate pteraspid heterostracans are described from the Middle Devonian beds of two formations in western North America. The late Givetian Yahatinda Formation of Alberta and British Columbia consists of channels cut into lower Paleozoic rocks and represents deposition in marine to littoral environments. Clavulaspis finis new genus new combination, is redescribed from additional material from the Yahatinda Formation and renamed, as the original genus name has proved to be invalid. The Eifelian Spring Mountain beds of Idaho consist of a large channel that represents a clastic dominated estuarine environment. It contains Scutellaspis wilsoni new genus new species, and the previously described species from the Spring Mountain beds is redescribed as Ecphymaspis idahoensis new genus new combination, prompted ...本报告记述了最晚的翼甲类（pteraspids）——一类隶属于异甲类（Heterostraci）的带甲无颌类成员，该类群此前仅发现于老红砂岩大陆（Old Red Sandstone Continent）的早泥盆世（Early Devonian）地层中。本次在北美西部两个地层的中泥盆世（Middle Devonian）岩层中记述了具瘤状纹饰的翼甲异甲类。产于阿尔伯塔省与不列颠哥伦比亚省的晚吉维特期（Givetian）亚哈廷达组（Yahatinda Formation）为一套切割下古生界（lower Paleozoic）岩层的水道沉积，代表海相至滨海环境的沉积产物。基于亚哈廷达组的新材料，对新属新组合Clavulaspis finis进行了重新描述并予以更名，因原属名已被证实无效。爱达荷州艾费尔期（Eifelian）的斯普林山层位（Spring Mountain beds）为一套大型水道沉积，代表以碎屑岩为主的河口湾环境，其中产出新属新种Scutellaspis wilsoni；此前记述的斯普林山层位物种，现被重新命名为新属新组合Ecphymaspis idahoensis，相关调整系因……