Proceroecia Kock, 1992

Benassi, G., Ferrari, I., Menozzi, P. & McKenzie, K. G., 1994, Planktic ostracodes from the antarctic and subantarctic collected by the 1989 – 1990 Italian Antarctic Expedition, Records of the Australian Museum 46 (1), pp. 25-37 : 27-28

Proceroecia Kock, 1992

Type species. Proceroecia microprocera ( Angel, 1971) .

Amended diagnosis. Conchoeciine genus in which the shells are small to moderate sized (up to 1.8 mm in length), relatively thin and fragile, striated, with asymmetric compound glands in the usual places (ie, posterodorsal in the LV, posteroventral in the RV), but lacking lateral corner glands and with dorsomedial glands only in the males, plus abundant medial glands along virtually the entire free margins of the valves. Usually, the RV carries a minute posterodorsal spinule.

In the soft anatomy: 1. The cap of the frontal organ in males carries long hairs ventrally and is more or less rounded terminally; in females, the frontal organ is long and slender, the cap is indistinctly jointed from the stem and is adorned with short prickly hairs ventrodistally.

2. The female antennule is short and without a dorsal bristle on the second segment; the 'e' bristle of the male has an armature consisting of biserial slender or bladelike, backwards-directed spinules.

3. The pipe bristles of the antennal endopod are relatively long in females but much shorter in males; both male endopod clasping organs are recurved strongly and stout proximally, the right one being better developed.

4. The masticatory pad of the mandible coxale is subrectangular, densely spinulose, undivided and straight-edged ventrally; the mandible exopod is well developed, its basal part resembling a cocked pistol in lateral profile; the first endopod segment of the mandible endopod carries at most only 2 (usually none or 1) long annulate ventral bristles, with or without up to 3 associated minute setules, usually set on a lunate ventrodistal bulge.

5. The furca is without a dorsal bristle.

Remarks. Poulsen (1973) included the 'procera' group of Mueller (1906) in his very broad interpretation of the genus Paraconchoecia Claus, 1891 , based on a perceived general similarity in the masticatory pad of the mandible coxale.

The type species of Paraconchoecia is Paraconchoecia oblonga (Claus, 1890) . We note further that P. gracilis (Claus, 1890) , another of the four species including oblonga that were originally assigned to Paraconchoecia by Claus (1891), is generally regarded as a junior synonym of Conchoecia elegans Sars, 1866 , which was made the type species of a new genus Discoconchoecia by Martens (1979).

In the strict sense, Paraconchoecia comprises only P. oblonga , P. spinifera (Claus, 1890) and P. allotherium ( Mueller, 1906) . It is simply differentiated from Proceroecia by having smooth (not striated) valves, and three or four ventral bristles without associated minute setules on the first endopod segment of the mandible which, unlike the case in Proceroecia , does not display a more or less lunate ventrodistal bulge.

Discoconchoecia Martens, 1979 is most easily distinguished from Proceroecia by the disc-like armature of the male antennule 'e' bristle, and by the fact that the first endopod segment of the mandible has two or three ventral bristles without any associated minute setules.

All other species brought by Poulsen (1973) into the aegis of Paraconchoecia , and thereby associated with Proceroecia by having a similar undivided, ventrally straight-edged masticatory pad on the mandible coxale, have four ventral bristles without any associated minute setules on the first endopod segment of the mandible; apart from several other differentiating features, including size, type of reticulation, positions of the asymmetric compound glands, shape of the male clasping organs, etc.

Additionally, Proceroecia species (= 'procera' group of Mueller, 1906) are identified rather readily by the mandible exopod, with its distinctive cocked-pistol lateral profile basally and long pilose extruding bristle, a feature which also provides a convenient name for our new species.

Proceroecia includes at least the following species: P. rivoltella n.sp.; P. procera (Mueller, 1894) ; P. brachyaskos ( Mueller, 1906) ; P. decipiens ( Mueller, 1906) ; P. vitiazi (Rudjakov, 1962) ; P. macroprocera ( Angel, 1971) ; P. microprocera ( Angel, 1971) ; P. hoensis ( Poulsen, 1973) . Recently, Angel (personal communication, June 1992) has provided a lengthy list of occurrences determined as P. brachyaskos in deep waters of the Atlantic Ocean at tropical latitudes. The mandibular endopod (first segment) of this taxon needs to be rechecked as it may well represent yet another species of Proceroecia .