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Peter Funch

A holomorph approach to xiphosuran evolution : a case study on the ontogeny of Euproops

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  • Carolin Haug, Yale University, United States
  • Peter Van Roy, Ghent University, Belgium
  • Angelika Leipner, Museum am Schölerberg, Germany
  • Peter Funch
  • David M. Rudkin, Royal Ontario Museum, Canada
  • Lothar Schöllmann, LWL-Museum für Naturkunde, Germany
  • Joachim T. Haug, Yale University, United States

Specimens of Euproops sp. (Xiphosura, Chelicerata) from the Carboniferous Piesberg quarry near Osnabrück, Germany, represent a relatively complete growth series of ten 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.

Original languageEnglish
JournalDevelopment, Genes and Evolution
Volume222
Issue5
Pages (from-to)253-268
ISSN0949-944X
DOIs
Publication statusPublished - 12 Aug 2012

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