Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, New South Wales, 2351, Australia.
Geological Institute, Russian Academy of Sciences, Moscow, Russia, 119117.
Naturwissenschaften. 2020 Oct 3;107(5):46. doi: 10.1007/s00114-020-01701-1.
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.
剑尾目是现存的海洋螯肢动物，它们在其约 4.8 亿年的化石记录中表现出明显的形态保守性和显著的生存能力。即使是最早的剑尾目动物也具有明显的特征，如新月形的前体和通常为梯形的胸板（后体），这引发了关于它们起源和分类意义的争论。这种兴趣导致在 20 世纪早期到中期，特别是在俄罗斯，描述了许多马蹄蟹物种，这些物种自最初发表以来一直未经修订，并且没有根据最近的系统发育假说进行考虑。在这里，我们重新检查了圣彼得堡切尔尼谢夫中央地质勘探博物馆中存放的非贝尔尼urid 分类单元。我们首次正式诊断了 Bellinuroopsis rossicus，直立的 Shpineviolimulus jakovlevi（Glushenko 和 Ivanov，1961）comb. nov.，其中包含以前被描述为“Paleolimulus”jakovlevi 的物种，并将 Paleolimulus juresanensis 归入 Paleolimulidae incertae sedis。系统发育分析将 S. jakovlevi 置于 Limulina 的基部。这种位置，加上前体盾明显大于胸板，以及缺乏肥大的侧刺，表明这种形态可能代表了祖先的 Austrolimulidae 形状。作为这次修订的扩展，我们评估了一般的 Austrolimulidae 形态特征，并发现了这些奇异的剑尾目动物的两个可能的群体。
