Contributions to Zoology, 83 (2) – 2014Pablo Hernández-Alcántara; Vivianne Solís-Weiss: Anatomical and morphometric analysis of a new species of Leitoscoloplos (Annelida: Orbiniidae) with numerous stomach papillae, from the Gulf of California, Eastern Pacific

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The morphological and morphometric analyses of 88 orbiniids from the continental shelf of the Gulf of California lacking thoracic neuropodial hooks confirmed that a new species, Leito­scoloplos multipapillatus, described herein, is present along with Leitoscoloplos panamensis (Monro. 1933), already recorded there. The new species is closely related to L. panamensis, but can be clearly separated from this, and all other species of Leito­scoloplos, by the unique presence of up to 14 stomach papillae per chaetiger. A third taxon was identified, Leitoscoloplos sp., which is morphologically indistinguishable from L. panamensis, except for the presence of 1-2 stomach papillae on 1-2 segments, a feature that although important was not considered significant enough to erect a new species. Morphometric analyses between the closely related species, L. panamensis (including its type material) and L. multipapillatus sp. nov., in addition to Leito­scoloplos sp., were used to verify the new species. The generic diagnosis is emended to include species with numerous stomach papillae. Anatomical examination of these species was carried out with SEM to illustrate their characteristic features and corroborate the presence of capillary chaetae only along the thorax of the analysed specimens, as well as the unusual occurrence of stomach papillae.