The group Xiphosurida (horseshoe “crabs”) is today only represented by four species. However, in the fossil record, several dozen species have been described, especially from the Carboniferous (about 300 million years ago). Several species have been interpreted as representatives of Euproops or Belinurus, but there is ongoing discussion which of these species are valid and how they can be differentiated. Recent studies suggested that differences in the timing of individual development could provide information for species distinction, exemplified by studies on Euproops danae (Mazon Creek, USA) and Euproops sp. (“Piesproops”; Piesberg, Germany). For this study, we reinvestigated all Carboniferous xiphosurids from the British Coal Measures stored in the collections of the Natural History Museum London. Size comparisons of the specimens revealed nine size groups; the smaller specimens were originally labelled as Belinurus, the larger ones as Euproops. The nine size groups exhibit five different morphotypes differing in structures surrounding the posterior shield (= thoracetron): spines of different lengths and, in larger specimens, a more or less developed flange. Two of these morphotypes show significantly longer spines than the remaining specimens and could be conspecific as E. anthrax. The remaining specimens are interpreted as growth series of another species, presumably of E. rotundatus. An ontogenetic flange formation is also known from E. danae and the “Piesproops”, but the timing differs between all three species. In E. rotundatus, the flange develops rather late, but then comparably abruptly, which makes this development more metamorphic in relation to development in the other species.

中文翻译：

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解开高迪氏结，进一步解决了3亿年前的剑突类鱼类的超物种复合体的问题，方法是重建它们的个体。

如今，Xiphosurida组（马蹄蟹）仅由四个物种代表。然而，在化石记录中，已经描述了数十种，特别是来自石炭纪的物种（大约3亿年前）。一些物种已被解释为代表优原穴鲎或Belinurus，但有持续的讨论这些物种是有效的，如何将它们区分开。最近的研究表明，个体发育时间的差异可以为物种区分提供信息，例如对丹参（Eupropops danae）（美国马佐恩克里克）和Euproops进行的研究就证明了这一点。sp。（“ Piesproops”；德国皮斯堡）。在本研究中，我们对伦敦自然历史博物馆藏品中存储的所有英国石炭纪石炭纪剑藻类生物进行了重新调查。标本的尺寸比较显示了九个尺寸组。较小的标本最初打成Belinurus，是较大的为优原穴鲎。九个大小的组显示出五种不同的形态学类型，这些形态在后盾（= thoracetron）周围的结构上不同：长短不一的棘突，在较大的标本中，或多或少发育出突缘。这些形态中的两种表现出比其余标本明显更长的棘突，并且可能与大肠杆菌一样具有特异性。。其余的标本被解释为另一种可能是圆形大肠埃希菌的生长系列。达纳肠球菌（E. danae）和“ Piesproops”也已知有自生的凸缘形成，但是这三个物种之间的时机不同。在E. rotundatus中，轮缘发育较晚，但随后相当突然，这使得这种发育相对于其他物种的发育更加变质。