Zoological Institute and Museum, Department of Cytology and Evolutionary Biology, University of Greifswald, Soldmannstrasse 23, 17487 Greifswald, Germany.
Dev Genes Evol. 2012 Sep;222(5):253-68. doi: 10.1007/s00427-012-0407-7. Epub 2012 Aug 10.
Specimens of Euproops sp. (Xiphosura, Chelicerata) from the Carboniferous Piesberg quarry near Osnabrück, Germany, represent a relatively complete growth series of 10 stages. Based on this growth sequence, morphological changes throughout the ontogeny can be identified. The major change affects the shape of the epimera of the opisthosoma. In earlier stages, they appear very spine-like, whereas in later stages the bases of these spine-like structures become broader; the broadened bases are then successively drawn out distally. In the most mature stage known, the epimera are of trapezoidal shape and approach each other closely to form a complete flange around the thoracetron (=fused tergites of the opisthosoma). These ontogenetic changes question the taxonomic status of different species of Euproops, as the latter appear to correspond to different stages of the ontogenetic series reconstructed from the Piesberg specimens. This means that supposed separate species could, in fact, represent different growth stages of a single species. It could alternatively indicate that heterochrony (=evolutionary change of developmental timing) plays an important role in the evolution of Xiphosura. We propose a holomorph approach, i.e., reconstructing ontogenetic sequences for fossil and extant species as a sound basis for a taxonomic, phylogenetic, and evolutionary discussion of Xiphosura.
德国奥斯纳布吕克附近皮埃斯堡采石场的碳纪 Euproops 属（Xiphosura，蛛形纲）标本代表了一个相对完整的 10 个阶段的生长序列。基于这个生长序列，可以确定整个个体发生过程中的形态变化。主要的变化影响到后体胸板的腹板的形状。在早期阶段，它们看起来非常像刺，而在后期，这些刺状结构的基部变得更宽；然后，这些变宽的基部逐渐向远端延伸。在已知的最成熟阶段，腹板呈梯形，彼此非常接近，在后胸腹板（=融合的体节）周围形成一个完整的边缘。这些个体发生的变化对不同种 Euproops 的分类地位提出了质疑，因为后者似乎对应于从皮埃斯堡标本重建的个体发生系列的不同阶段。这意味着假定的不同物种实际上可能代表单一物种的不同生长阶段。或者这可能表明，异时性（=发育时间的进化变化）在 Xiphosura 的进化中起着重要作用。我们提出了一种整体形态方法，即重建化石和现存物种的个体发生序列，作为对 Xiphosura 的分类、系统发育和进化讨论的可靠基础。
