Naturwissenschaften

, 98:889 | Cite as

Sperm carriers in Silurian sea scorpions

Original Paper

Abstract

Invasion of the land by arachnids required adaptations of numerous organs, such as gills evolving into lungs, as well as mechanisms facilitating sperm transfer in a terrestrial environment. Many modern arachnids use spermatophores for this purpose, i.e. sperm transmitters detached from the body. Exceptionally preserved Silurian (423 Ma) fossils of Eurypterus tetragonophthalmus Fischer, 1839 (Chelicerata: Eurypterida) preserve so-called ‘horn organs’ which we here demonstrate as being equivalent to the spermatophore-producing parts of the genital tract in certain modern arachnids. This clarifies a long-running debate about sexing eurypterids based on the shape of the median abdominal (or genital) appendage. To our knowledge this is also the oldest direct evidence for spermatophore-mediated sperm transfer in the fossil record and suggests that eurypterids had evolved mating techniques using spermatophores as early as the Silurian, a valuable prerequisite for life on land. Spermatophores are absent in sea spiders (Pycnogonida) and horseshoe crabs (Xiphosura); thus the shared presence of sclerotized sperm-transfer devices in eurypterids and arachnids is a novel character, newly elucidated here, which offers explicit support for (Eurypterida + Arachnida). For this clade the name Sclerophorata n. nov. is proposed. Arachnida can be further defined by fusion of the originally paired genital opening.

Keywords

Fossil Silurian Eurypterida Arachnida Spermatophore Evolution 

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Carsten Kamenz
    • 1
  • Andreas Staude
    • 2
  • Jason A. Dunlop
    • 3
  1. 1.American Museum of Natural HistoryNew YorkUSA
  2. 2.Federal Institute for Materials Research and Testing (BAM)BerlinGermany
  3. 3.Museum für Naturkunde, Leibniz Institute for Research on Evolution and BiodiversityHumboldt University BerlinBerlinGermany

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