Establishment of a new subfamily of Idyanthidae Lang, 1944 with the description of a new species of Pseudometeorina George & Wiest, 2015 (Copepoda, Harpacticoida) from the Eratosthenes Seamount (eastern Mediterranean Sea)

The description of Pseudometeorina eratosthenica sp. nov. from the eastern Mediterranean Eratosthenes Seamount was the release for a detailed phylogenetic comparison of a group of derived representatives of the family Idyanthidae Lang, 1944, namely Aspinothorax Moura & Martinez Arbizu, 2003, Meteorina George, 2004, Pseudometeorina George & Wiest, 2015, and Styracothorax Huys,1993. The named genera share the derived presence of a 2-segmented P1 exopod as well as the transverse elongation of the bases of the swimming legs P1-P4, being these five deviations unique for Idyanthidae and therefore hypothesized here as synapomorphic for the above-named taxa. Consequently, they are pooled in the newly established Aspinothoracinae Moura & Mar tinez Arbizu, 2003 subfam. nov. The new species described from Eratosthenes Seamount doubtlessly belongs to Pseudometeorina, sharing with P. mystica George & Wiest, 2015, a set of 24 synapomor-phies. Otherwise, P. eratosthenica sp. nov. provides nine autapomorphies that justify its establishment as distinct species. A detailed phylogenetic analysis, based on 131 morphological characters, is presented. Moreover, a key to the species of Aspinothoracinae subfam. nov. is provided.