Review and phylogeny of the Recent Polycopidae (Ostracoda, Cladocopina), with descriptions of nine new species, one new genus, and one new subgenus from the deep South Atlantic

Abstract

Polycopidae Sars, 1866 ostracods from the DIVA II expedition of the RV “Meteor” at the Cape, Angola, and Guinea basins are presented here. They were collected between 26 February and 30 March 2005, from depths between 5,047 and 5,150 m. Metapolycope divae sp. nov. belongs to the subfamily Polycopsisinae Chavtur, 1983, and stands apart from the other representatives of the genus by the morphology of the uropodal lamellae. The remaining eight new species described herein belong to the subfamily Polycopinae Sars, 1866. The genus Archypolycope Chavtur, 1981 is represented in the investigated area by four new species: A. atlantica sp. nov., A. brandtae sp. nov., A. louisi sp. nov., and A. martinezi sp. nov. With the addition of these four new species, this genus is redefined to include six Recent and three fossil species. Archypolycope atlantica is the only representative in the family with six bristles ventrally on the first segment of the mandibula. The other three new species stand apart by the specific shell ornamentation, chaetotaxy of the maxillula, and morphology of the uropodal lamellae. Archypolycope cornea Chavtur, 1981 and A. rotunda Chavtur, 1981, both described from the abyssal depths of the Kuril-Kamchatka trench, are here excluded from the genus. The decision is based on the absence of the peculiar morphology of the fifth limb endopod, which is shared by all other Archypolycope. These species are transferred to the genus Pseudopolycope Chavtur, 1981, because they have a fifth limb endopod consisting of a segment and one terminal bristle, but are placed in separate new subgenus Divacope subgen. nov. The new subgenus differs from the nominotypical subgenus by a much shorter fusion of the two bristles on the Bellonci Organ, and by the presence of hooks on the male antenna. Besides Pseudopolycope (D.) cornea (Chavtur, 1981) comb. nov. and P. (D.) rotunda (Chavtur, 1981) comb. nov, the subgenus has been defined to include one more member: P. (D.) chavturi sp. nov., which is also described from the deep South Atlantic and designated the type species of the new subgenus. It is most closely related to P. (D.) cornea, but differs from it by the chaetotaxy of the antennula and morphology of the exopod mandibula. Two new species, P. (P.) quasivitjazi sp. nov. and P. (P.) spio sp. nov., from the deep South Atlantic are added to the nominotypical subgenus, which now has 15 Recent species. One of the new species described here could not be accommodated into any of the known Polycopinae genera, so the new genus Hyphalocope gen. nov. was erected for it, and defined by the following autapomorphies: completely flat dorsal margin of the shell, presence of the bifurcated bristles on the shell, elongated antennula, and very long Bellonci Organ. Presently, Hyphalocope dorsoithys gen. et sp. nov. is known only from females. We provide a key to genera of the family Polycopidae, and keys to species of the genera Metapolycope, Archypolycope, and Pseudopolycope. In order to learn about the phylogenetic relationships and to point out some current problems of polyphyletic and paraphyletic genera in the subfamily Polycopinae, we perform a cladistic analysis based on 29 morphological characters scored for 91 Recent species. Two species from the genus Metapolycope are chosen as outgroups. Extensive discussion on the distribution and suitability of morphological characters in this family is also provided. All Recent species of Polycopidae are listed at the end, with information about their geographic and bathymetric distributions, habitat, presence of sexes, and body length.