TY - JOUR A1 - Kamenz, C. A1 - Staude, Andreas A1 - Dunlop, J.A. T1 - Sperm carriers in silurian sea scorpions JF - Naturwissenschaften N2 - 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 spermatophoremediated 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. KW - Fossil KW - Silurian KW - Eurypterida KW - Arachnida KW - Spermatophore KW - Evolution PY - 2011 DO - https://doi.org/10.1007/s00114-011-0841-9 SN - 0933-4793 VL - 98 IS - 10 SP - 889 EP - 896 PB - Schäuble CY - Rheinfelden AN - OPUS4-24552 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -