Size matters: a new genus of tarantula with the longest male palps, and an integrative revision of Monocentropus Pocock, 1897 (Araneae, Theraphosidae, Eumenophorinae)

A taxonomic revision of the eumenophorine tarantula genus <i>Monocentropus</i> Pocock, 1897, which currently comprises three species, <i>M.balfouri</i> Pocock, 1897 (♂♀; Socotra, Yemen), <i>M.lambertoni</i> Fage, 1922 (♂♀; Madagascar), and <i>M.longimanus</i> Pocock, 1903 (♂♀; Yemen), is presented. By integrating both morphological data and a molecular phylogeny based on mitochondrial (<i>cox1</i>) and nuclear (<i>28S</i>, <i>18S</i>) markers, the genus is herein redefined to include only the type species, <i>M.balfouri</i>. A new genus, <i>Satyrex</i> Zamani & von Wirth, <b>gen. nov.</b>, is established to comprise <i>S.longimanus</i> <b>comb. nov.</b>, along with four new species from the Arabian Peninsula and the Horn of Africa described herein: <i>S.arabicus</i> Zamani & von Wirth, <b>sp. nov.</b> (♂; Saudi Arabia), <i>S.ferox</i> Zamani, von Wirth & Stockmann, <b>sp. nov.</b> (♂♀; Yemen, Oman), <i>S.somalicus</i> Zamani & von Wirth, <b>sp. nov.</b> (♂; Somaliland), and <i>S.speciosus</i> Zamani, von Wirth & Just, <b>sp. nov.</b> (♂♀; Somaliland). The new genus is partially characterised by possessing the longest male palps known in tarantulas, possibly functioning in cannibalism avoidance during mating. Both the molecular phylogeny and morphological characters suggest that <i>M.lambertoni</i> is probably not congeneric with <i>M.balfouri</i>, and also indicate that multiple species may be currently subsumed under the former name. Therefore, <i>M.lambertoni</i> is regarded as incerta sedis pending further studies to clarify its taxonomic placement, as it is also considered to represent a species complex. Finally, the distribution of all studied taxa is discussed within a biogeographic framework.