Xiphosura are extant marine chelicerates that have displayed apparent morphological conservatism and remarkable survivorship across their ~ 480 Ma fossil record. The easily recognisable features that are known to even the earliest xiphosurans—a crescentic prosoma and often trapezoidal thoracetron (opisthosoma)—have generated debate surrounding their origins and taxonomic significance. This interest resulted in the description of numerous horseshoe crab species during the early to mid-twentieth century, particularly in Russia, that have remained unrevised since their original publications and unconsidered in the light of recent phylogenetic hypotheses. Here, we re-examine the non-belinurid taxa housed within the Chernyshev Central Museum for Geological Exploration in Saint Petersburg. We present the first formal diagnosis of Bellinuroopsis rossicus, erect Shpineviolimulus jakovlevi (Glushenko and Ivanov, 1961) comb. nov., to contain the species formerly described as ‘Paleolimulus’ jakovlevi and refer Paleolimulus juresanensis to Paleolimulidae incertae sedis. Phylogenetic analysis places S. jakovlevi at the base of Limulina. This position, coupled with a prosomal shield that is notably larger than the thoracetron, and lack of hypertrophied genal spines, suggests that this morphology may represent the ancestral austrolimulid shape. As an extension of this revision, we assessed the general austrolimulid morphological characters and uncovered two possible groups of these bizarre xiphosurids.

剑尾龙是现存的海洋螯虫，在大约 480 Ma 的化石记录中表现出明显的形态保守性和显着的存活率。即使是最早的 xiphosurans 也知道其易于识别的特征——新月形前体和通常呈梯形的胸甲体（opisthosoma）——引起了围绕其起源和分类学意义的争论。这种兴趣导致了二十世纪早期到中期对许多鲎物种的描述，特别是在俄罗斯，这些描述自最初发表以来一直没有修订，也没有根据最近的系统发育假设进行考虑。在这里，我们重新审视圣彼得堡切尔尼雪夫中央地质勘探博物馆内的非贝利努科类群。我们提出了对Bellinuroopsis rossicus的首次正式诊断，即直立的Shpineviolimulus jakovlevi （Glushenko 和 Ivanov，1961）鸡冠。 11 月，包含以前被描述为“ Paleolimulus ” jakovlevi的物种，并将Paleolimulus juresanensis归为 Paleolimulidae incertae sedis 。系统发育分析将S. jakovlevi置于 Limulina 的基部。这个位置，加上明显大于胸脑的前体盾，并且缺乏肥大的生殖棘，表明这种形态可能代表了祖先的 austrolimulid 形状。作为本次修订的延伸，我们评估了 austrolimulid 的一般形态特征，并发现了这些奇怪的 xiphosurid 的两个可能的群体。