Gerdocypris, a new genus of Paracyprididae (Ostracoda) from the North Atlantic, Mediterranean and East Africa

The genus Gerdocypris (type species Gerdocypris muelleri sp. nov.) is described as new based on a mature male from the Bay of Naples. Gerdocypris ranges from the North Atlantic and Mediterranean to East Africa. Its differences from Aglaiocypris and Aglaiella are discussed and tabulated.

and regularly curved; P3 h e g m e n t e d , the long reflexed bristle jointed at about 213 its length from the proximal end; furcal lamella short and broad, with 2 strong stubby claws, an anterior bristle and 2 longish posterior bristles; rake like organ with 14 small teeth. Hemipenis with coils opening ventrally, peniferum digitate; Zenkers Organ with 5 whorls; endopods of the male P1 symmetrical, i.e. not dissimilar on right and left of the body. Remarks. McKenzie (1982, pp. 416-417) points out that Agluia complunata (Brady & Robertson, 1870) which was figured in the American Treatise (Moore, 1961) as representing Aglaiocypris is not an example of this genus, having a different radial pore canal pattern and a different soft anatomy. The former character has been confirmed from examination of specimens of A . complanata in the Norman Collection at the British Museum (Natural History). Unfortunately, n o dissection slides for the taxon are available in the BM (NH) collections.
The finding recently of a mature male of the species identified by G.W. Miiller (1894) as A . complanata enables a more detailed comparison with the male described by Brady (1868) among the syntypes ofAglaia pulchellu Brady, 1868 which is the type species of Aglaiocypris. The re-illustration of the type of Aglaiella (McKenzie, 1982, Pls. 5, 6) also enables a comparison with that genus (Table 1).
In addition to the data presented in Table 1, Aglaiella differs from Gerdocypris in that the reduced 'natatory' setae of the antennae are somewhat longer in Aglaiella and more numerous (5 in Aglaiellu versus 3 in Gerdocypris).
Derivation of name. After G.W. Miiller, who described and illustrated this taxon asA. complanata in his Bay of Naples monograph (Miiller, 1894 regularly elongate bean-shaped and weakly calcified; greatest height medial and less than half the length; dorsum regularly arched; venter inflexed near-medially; anterior and posterior margins subequally rounded, the posterior slightly narrower. In dorsal view, elongate subelliptical; greatest width medial and less than half the length; extremities subacuminate. Surface of the valves smooth; colour whitish. Inner lamellae broad anteriorly and ventrally, narrow posteriorly; line of concrescence submarginal; consequently the radial pore canals are very short and straight (not particularly numerous) except ventrally where a few are longer; normal pore canals scattered, simple, rimmed; muscle scars comprising a cypridacean rosette of 3 anterior and 2 posterior adductors (the uppermost adductor divided), a fulcra1 scar, plus 2 small mandibular scars (PI. 1, fig. 1). Antennule 5-segmented; length ratios of the segments about 5:1:3:1:0.5; 1st segment with a proximodorsal and 2 long ventrodistal bristles; 2nd segment with a dorsodistal bristle; 3rd segment carrying 1 mediodorsal and 1 mediodistal bristle; 4th segment with 4 bristles, 3 of them long and 1 very long; 5th segment with 4 terminal bristles, 3 long (including 1 very long) and 1 short and slender (Pl. 1, fig. 2).
Antenna 6-segmented; comprising coxale, basale, exopod and endopod. Coxale with 2 unequal relatively short ventrodistal bristles; basale with a long ventrodistal bristle. Exopod reduced to a small baseplate bearing 3 unequal bristles, 1 about half the length of the 1st endopod segment, the remaining 2 very small. Endopod 4-segmented; length ratios of the segments 11:4:4:2; 1st segment with a well developed near proximal Y-aesthetasc, a ventrodistal bristle and a small subventrodistal clump of 3 short bristles (which are the strongly reduced relicts of natatory bristles); 2nd segment with a medioventral bristle and 2 distal bristles, plus a ventrodistal claw; 3rd segment with 2 distal claws and a distal bristle, the 2 claws dorsal (1 of them very strong), the bristle ventral and short; 4th segment with a strong distal claw and 2 slender distal bristles (Pl. 1, fig. 3).  Mandible comprising coxale, basale, epipod and endopod. Coxale with at least 4 strong teeth, the anteriormost incisor-like, the others molar-like and decreasing in size from front t o rear, plus a medial anterior bristle and 2 small sideways-directed posteroventral bristles. Basale with 3 ventral bristles, one of them a slender (Y bristle. Epipod with at least 4 Strahlen. Endopod .?-segmented; length ratios of the segments 3:4:2; 1st segment with a dorsodistal bristle and a clump o f at least 3 (and probably 4) ventrodistal bristles, but a p bristle could not be distinguished; 2nd segment with 5 dorsodistal bristles, a mediodistal bristle and 2 ventrodistal bristles (the mediodistal bristle undifferentiated); 3rd segment with 2 terminal claws (one larger than the other) and at least 1 slender terminal bristle (PI. 1, fig. 4).
P2 (Walking Leg) with a 4-segmented endopod; length ratios o f the segments 12:6:6: 1.5; 1st and 2nd segments each bearing a ventrodistal bristle of similar length; 3rd segment with a short ventrodistal bristle; 4th segment with single short ventro-and dorsodistal bristles plus a long. slender and regularly curved tcrminal claw (PI. I , figs. 14, 15). P3 (Cleaning Limb) retlexed, 5-segmented; length ratios of the last 4 segments about lO:6:6: 1.7; 1st segment with at least 1 long bristle (ventrodistally); 2nd segment and 3rd segment each bearing a dorsodistal bristle of similar length; 4th segment with a short dorsodistal bristle; 5th segment with a short terminal bristle and 2 opposed larger bristles, the smaller of these clawlike (about twice the length o f the short bristle) and the larger about 3 times longer than the claw-like bristle and divided at about '/:< its length from t h e proximal end (PI. 1 , figs. 1 0 , 1 1 ) .
Furca bilamellar, short and broad; each lamella with 2 strong, stubby terminal claws which are spinose distally, plus a slender antcrodistal bristle and 2 nearly equal slender bristles (almost as long as the claws) o n the margin behind the posterior claw but well separated from it and from each other (Pl. 1, fig. 13).
Chitin Support thick, rather pointed at the end where it connects with the furca and forked proximally with a large eyelet in the fork (PI. 1, fig. 9).
Hemipenis subquadrate; anterior lobes rather broadly rounded; seminal tube complexly coiled, the coils opening downwards; copulatory process broadly pointed, digitate (PI. 1, fig. 12). a left valve, is mature and higher with respect to its length also more robustly calcified than Gerdocypris rnuelleri. It, too, lacks soft parts. Due to the unsatisfactory nature of these specimens, it seems preferable at this stage t o describe G. muelleri as a new species, while recognising that better and topotypic material of A . complunata may lead subsequently t o the synonymising o f rnuelleri with complanutu.
Another species which clearly belongs in Gerdocypris is Agluiocypris eulitorulis Hartmann, 1974. The soft parts o f A . eulitorulis are very close to those o f G. muelleri, except that on the furca the posterior of the 2 bristles on the ventral margin of the lamella is about twice as long as the anterior vcntromarginal bristle, whereas in G. muelleri this bristle is only slightly longer than the anterior ventromarginal bristle. In size and shape A . eulitorulis is smaller and somewhat higher with respect to its length than G. muelleri (Hartmann, 1 Y74, PI. 144, figs. 095-1005).
Holotype 0.73 0.295 The genus is distributed through the North Atlantic (complanutu), in the Mediterranean (muelleri) and o n the coast of East Africa (eulitoralis); at depths ranging from the littoral to about S0m.