Schornikovoecia, Chavtur & Bashmanov, 2018

Chavtur, Vladimir G. & Bashmanov, Alexander G., 2018, Schornikovoecia eugenyi, a novel species and genus of deep benthopelagic halocyprids (Ostracoda, Myodocopa) from the North-west Pacific, Zootaxa 4527 (2), pp. 197-210 : 199-200

Schornikovoecia gen. nov. Chavtur, 2018

Etymology. The genus is named in honour of the famous ostracodologist Eugeni Ivanovich Schornikov (1938- 2016), who worked at the Institute of Marine Biology, Far Eastern Branch of Russian Academy Sciences, Russia.

Type species: Schornikovoecia eugenyi sp. nov. Chavtur

Species composition. At present the genus is monospecific, but may also include an undescribed species Bathyconchoecia sp. nov. Atlantic “B” ( Angel 2010).

Diagnosis. Carapace. Length range 4.02–4.16 mm in adult males; 3.76–4.0 mm in adult females. Posterodorsal corner of each valve with small but distinct point armed with a row of denticles. Posterior margin of carapace with single row of dentate structures running from below the opening of the carapace glands and decreasing in size towards the postero-ventral corner. Large asymmetrical glands have sclerotized capsules near its openings and are located beneath the postero-dorsal points. Carapace sculpture looks like the vertical and oblique rows of narrow, elongated “scales”.

First antenna. Second segment lacks ventral setae.

Mandible. There is a strongly sclerotized knob-like articular process on the coxa. The masticatory pad is almost spherical: its ventral half is densely covered with short spines and its dorsal surface has numerous minute flabby denticles. The distal and proximal tooth lists are fused. The basale endite, as is usual in the subfamily, is edged with a row of six triangular teeth with similar outer tooth, a small tube-like seta (which leans on the adjacent triangular tooth) and a short spine-like seta.

Fifth limb. The basale has nine typical setae and a cluster of five to seven (five or six in males and seven in females) moderately long and slender setae on its disto-dorsal surface.

Description. Carapace. Length range 4.02–4.16 mm (n = 2) in adult males and 3.76–4.0 mm (n = 6) in females. It is moderately elongated. Rostrum large, straight and pointed. Anterior, ventral and posterior margins rounded and dorsal margin almost straight. Postero-dorsal corner of each valve with small but distinct point armed with a row of denticles. Posterior margin of carapace with single row of dentate structures running from below the opening of the carapace glands and decreasing in size towards the postero-ventral corner. Large asymmetrical glands have sclerotized capsules near its openings and are located beneath the postero-dorsal points. Carapace sculpture looks like vertical and oblique rows of narrow, elongated “scales” ( Fig. 2 , 3A and 8 ).

First antenna. Elongated and five-segmented. Second segment lacks ventral setae. Large oval cluster of sensory filaments on fourth segment consists of 10–12 rows, each having 25–30 filaments, a total of 250–300 filaments.

Second antenna. Structure of the endopodite in the female is typical of the Bathyconchoeciinae subfamily. Right clasping organ in male is large and sharply curved and carries three setae of different lengths. Left clasping organ smaller and bent back over its base; with three setae of different lengths. In the male, second endopodite segment with pair of minute pegs near the middle of the dorsal margin and one similar peg inserted near the base of its two setae. First exopodite segment with short slender seta near its terminal margin.

Mandible. With strongly sclerotized knob-like articular process on the coxa. The masticatory pad is almost spherical: its ventral half is densely covered with short spines and its dorsal surface has numerous minute flabby denticles. Distal and proximal tooth lists fused. Basale endite, as usual in the subfamily, edged with a row of six triangular teeth with similar outer tooth, a small tube-like seta (which leans on the adjacent triangular tooth) and a short spine-like seta. Ventral surface of first endopodite segment with one long and stout seta and two shorter and more slender setae.

Maxilla. Anterior margin of first endopodite segment with a group of four setae proximally and one seta distally. Posterior margin with only one seta. Distal edge of the segment with lateral row of five setae.

Fifth limb. Basale with nine typical setae and a cluster of five to seven (five or six in males and seven in females) moderately long and slender setae on its disto-dorsal surface. First endopodite segment with seven to nine (seven or eight in males and nine in females) ventral slender setae and three typical dorsal setae. The second segment has two typical setae and one claw-like seta.

Sixth limb. Precoxale bears three setae, coxale with three setae and basale with five ventral and one lateral seta, all of which are plumose. The exopodite is represented by extremely long dorsal setae. The first endopodite segment carries four to five ventral setae and five dorsal setae. Second segment with two ventral and five to six dorsal setae. Third segment with one long claw-like seta and two typical setae.

Seventh limb. Elongated and slender. Copulatory appendage. Elongated, almost straight, slim and rounded at the tip. The muscle bands are not distinguished. Caudal furca. Each lamella has eight slim and weak claws. Long unpaired seta behind the claws. Distribution. Ostracods of the genus Schornikovoecia were found in the north-western Pacific between 40°– 46°N, 150°–157°E and also in the Sea of Okhotsk in the area 48°N, 150°E at depth range from 3366 to 5419 m (see Table 1).

Figures

FIGURE 2. Schornikovoecia eugenyi sp. nov. (Adult female: SO223/001-11, length 4.0 mm). A, carapace; B, sculpture pattern of carapace.

FIGURE 3. Schornikovoecia eugenyi sp. nov. (Adult female: A, paratype MIMB 18357/2; B–G, holotype). A, right valve of carapace in lateral view; B and C, details of carapace: posterior dorsal corners in interior and exterior views; D, first antenna; E, distal part of first antenna; F, endopodite and first exopodite segment of second antenna; G, distal part of endopodite of second antenna.

FIGURE 8. Schornikovoecia eugenyi sp. nov. Carapace of A-1 juvenile (3.03 mm) in ventral view (St. 223/008-12; see Table).