Mcadams Neo E B, Adrain Jonathan M, Karim Talia S
Department of Earth and Environmental Sciences, University of Iowa, 115 Trowbridge Hall, Iowa City, Iowa 52242, USA..
Zootaxa. 2018 Nov 27;4525(1):1-152. doi: 10.11646/zootaxa.4525.1.1.
Field-based revision and phylogenetic analysis demonstrate that the pliomerid trilobite taxon Ibexaspis Přibyl and Vaněk (in Přibyl et al., 1985), previously known from a single formally named species (I. brevis [Young, 1973]), belongs to a complex of 14 mostly newly discovered, related species from the Early Ordovician (Floian; Tulean and Blackhillsian) of the northern Laurentian margin. The species are known from silicified samples recovered from sections in eastern Nevada, western Utah, and southeastern Idaho. The stratigraphically early Tuleaspis n. gen. (type species: T. jeneki n. sp.; Tulean; low Protopliomerella contracta Zone) includes its type and two species described in open nomenclature. Tuleaspis is sister to the remainder of the clade. Ibexaspis now includes three additional species: I. coadyi n. sp. (Blackhillsian; Carolinites nevadensis Zone), I. leuppi n. sp. (Blackhillsian; Presbynileus ibexensis Zone), and I. rupauli n. sp. (Blackhillsian; "Pseudocybele nasuta Zone"). Ibexapsis is sister to a clade of Millardaspis n. gen. + Deltapliomera n. gen. Millardaspis (type species M. milsteadi n. sp.; Tulean; Heckethornia hyndeae Zone) also includes M. knoxi n. sp. (Tulean; Panisaspis sevierensis Zone). Deltapliomera (type species D. humphriesi n. sp.; Blackhillsian, Carolinites nevadensis Zone) also includes D. inglei n. sp. (Tulean; Heckethornia bowiei Zone), D. heimbergi (Tulean; Panisaspis sevierensis Zone), D. eppersoni n. sp. (Blackhillsian; Bathyurina plicolabeona Zone), and a species described in open nomenclature.
基于野外的修订和系统发育分析表明，褶颊虫三叶虫分类单元伊比克斯盾虫Přibyl和Vaněk（见于Přibyl等人，1985年），此前仅知有一个正式命名的物种（I. brevis [Young，1973年]），属于一个包含14个主要是新发现的相关物种的类群，这些物种来自劳伦大陆边缘北部的早奥陶世（弗洛阶；图勒阶和布莱克希尔阶）。这些物种来自从内华达州东部、犹他州西部和爱达荷州东南部的剖面中采集的硅化样本。地层上较早的图勒盾虫新属（模式种：T. jeneki新种；图勒阶；低等的收缩原褶颊虫带）包括其模式种和另外两个以开放命名法描述的物种。图勒盾虫是该分支其余部分的姐妹群。伊比克斯盾虫现在包括另外三个物种：I. coadyi新种（布莱克希尔阶；内华达卡罗利特虫带）、I. leuppi新种（布莱克希尔阶；伊比克斯普雷斯比尼罗虫带）和I. rupauli新种（布莱克希尔阶；“鼻状假杯形虫带”）。伊比克斯盾虫是米勒德盾虫新属+三角褶颊虫新属分支的姐妹群。米勒德盾虫（模式种M. milsteadi新种；图勒阶；海德海克索尼亚虫带）还包括M. knoxi新种（图勒阶；塞维尔帕尼斯盾虫带）。三角褶颊虫（模式种D. humphriesi新种；布莱克希尔阶，内华达卡罗利特虫带）还包括D. inglei新种（图勒阶；鲍伊海克索尼亚虫带）、D. heimbergi（图勒阶；塞维尔帕尼斯盾虫带）、D. eppersoni新种（布莱克希尔阶；褶边深海虫带）以及一个以开放命名法描述的物种。
