Revision of the amphiamerican genus Mysidium Dana, 1852 (Crustacea: Mysida: Mysidae), with descriptions of two new species and the establishment of two new subgenera Author Wittmann, Karl J. Author Wirtz, Peter text European Journal of Taxonomy 2019 2019-02-05 495 1 48 journal article 28548 10.5852/ejt.2019.495 db716632-f55b-4a04-b3cd-918eea1c92c9 2584868 65CC1141-E560-4979-97E5-F0701563C84B Occimysidium Wittmann subgen. nov. urn:lsid:zoobank.org:act: EE9F05D3-29B5-4B95-BC0D-2A6756AAECE5 Type species Mysidium pumae Ortiz, Hendrickx & Winfield, 2017 , by monotypy. Etymology Noun in nominative singular with neutral ending, formed by amalgamation of the Latin noun ‘ occidens ’ with the generic name Mysidium , referring to the occurrence on the west coast of America. Diagnosis Subdivision of the genus Mysidium Dana, 1852 , characterized by two-segmented carpopropodus of third thoracic endopod; merus of this endopod without serrated setae. Third male pleopod with distinct endite at about ¾ distance from basis of medial margin. Sympod of fourth male pleopod without setae on rostral face. Its exopod four-segmented; basal segment with 0–1 seta, second segment without seta, subterminal segment with bifid modified seta, terminal segment with undivided modified seta. Telson entire (not incised). Distribution As for type species. Mysidium ( Occimysidium ) pumae Ortiz, Hendrickx & Winfield, 2017 comb. nov. Mysidium pumae Ortiz et al. , 2017a : 114 –117, table 1, figs 1–4. Mysidium pumae – Ortiz et al. 2017b : 77 . — Ortiz & Lalana 2018 : 80 . Material examined None. Type locality Pacific coast of Mexico , Mazatlán Harbor, 23.1814° N , 106.4242° W ( Ortiz et al. 2017a ). Revised definition Adapted to the scheme in Table 2 by using published data ( Ortiz et al. 2017a , 2017 b) on adults of both sexes: all features diagnosed above for the genus Mysidium Dana, 1852 , and its new subgenus Occimysidium . Cornea crescent-like in dorsal view, with ‘diameter’ 1.5 times as long as terminal segment of antennular trunk. Eyestalks smooth. Rostrum triangular, apically bluntly pointed, not extending beyond eyestalks. Appendix masculina with separate inner and distal tufts of setae; its length 2.0–2.2 times terminal segment of antennular trunk. Length of antennal scale six times maximum width; scale reaching well beyond antennular trunk. Median segment of mandibular palp with setae on both margins. Carpopropodus of first to eighth thoracic endopods 2, 2, 2, 3, 3, 3, 2, and two-segmented, respectively. Basal segment occupies 0.8 times total length of carpopropodus of endopod 3. Pleopods 1–2, 5 rodlike, not considering the reduced endopodal portion (pseudobranchial lobe); male pleopod 3 with an additional, small endite. Length of male pleopods increases in order of pleopods 1, (subequal 2, 3, 5), 4. Sympod of male pleopod 4 without endite. Exopod with basal segment occupying 54% total length. Endopod reduced to lobe with = 22% sympod length; apically with one long seta and more proximally four additional shorter setae. Uropodal endopod 0.7 times as long as exopod. Telson spatulate, caudally gradually narrowing; length 2.3 times maximum width near basis; terminal margin convex, evenly rounded. Proximal 51–52% of lateral margins smooth, distal portion of each margin with continuous series of 20–22 acute laminae. Terminal margin lined by 23–25 more densely set, acute laminae. These latter laminae more slender than the neighboring latero-terminal laminae. Distribution So far known only from type locality.