Description of Arcturinella deltensis sp. nov. (Crustacea, Isopoda, Arcturidae) from the Ebro Delta (Western Mediterranean Sea), with remarks on the status of the genus Arcturinella Poisson & Maury, 1931.

This paper includes the complete description of the new species Arcturinella deltensis and the comparison with the other species of the same genus, A. banyulensis. The holotype used by Poisson and Maury (<xref>1931</xref>) to describe A. banyulensis is currently missing. The unique specimen available was one female from Estepona, Málaga (Strait of Gibraltar area) cited by Rodríguez-Sánchez et al. (<xref>2001</xref>). The occurrence in the Ebro Delta (Iberian Peninsula) of some females belonging to genus Arcturinella is here reported. A detailed morphological study revealed that the specimens from the Ebro Delta have the same features as the female from Estepona and significant differences compared to A. banyulensis; consequently, A. deltensis sp. nov. is erected. The taxonomical status of A. banyulensis becomes uncertain because it cannot be proved whether its characters are described adequately. However, enough differences are detected among the analyzed specimens and the description and figures from Poisson and Maury (<xref>1931</xref>) to clearly justify the distinction of a new species. The genus Arcturinella is diagnosed as follows: body flattened dorsoventrally, not geniculate between pereonites 4 and 5; cephalon fused with pereonite 1, incomplete suture at the margins; pereonite 4 hexagonal and widest, with posterior margin not excavated; pleotelson without free segments, with lateral wings; mandibles rounded, pars incisiva and pars molaris absent; pereopods 1-4 reduced; pereopods 1-3 flattened and with articles not fused; pereopod 1 unguis absent; pereopods 2-4 dactyli absent; pereopod 4 vestigial, linear, with circular or angular section, with or without fused articles; brood-pouch of oostegites of pereonites 2-4; pereopods 5-7 with secondary unguis smaller than the primary unguis. [ABSTRACT FROM AUTHOR]