Eusarsiella elofsoni Kornicker 1986

Eusarsiella elofsoni

ETYMOLOGY.—The species is named for O. Elofson, who has contributed much to the study of myodocopid Ostracoda.

HOLOTYPE.—USNM 154181, ovigerous female on slides and in alcohol.

TYPE-LOCALITY.—R/V Gyre cruise 11, station 7, Gulf of Mexico, off Galveston, Texas, 53 m.

PARATYPES.—Texas continental shelf: USNM 193106, 1 ovigerous female, sta 6 off Port Isabel; USNM 193107, 1 juvenile, sta 3 near Southern Bank.

DISTRIBUTION.—Texas continental shelf at depths of 53–82 m (Figure 2, Table 1).

DESCRIPTION OF ADULT FEMALE (Figures 94, 95; Plates 28–30).—Carapace oval in lateral view with prominent posteroventral caudal process and without incisur (Figure 94; Plate 28a).

Ornamentation (Figures 94, 95a; Plates 28, 29a–c): Each valve with horizontal rib extending from near anterior or valve to just below valve middle where it intersects anterior end of alate rib extending to posterodorsal corner of valve; intersection of ribs located in vicinity of central adductor muscle attachments; posterior, anterior, and ventral edge of valve with prominent processes (Figure 94); posterior edge of valve with 4 processes (Figures 94, 95a); horizontal posterior edge of alate process with 3 processes including posterodorsal end of alate rib (a fourth process medial to 3 processes on the horizontal edge, all visible in dorsal view in Figure 94, is also the upper process on the posterior edge of valve); a narrow rib extending from posterior process on dorsal margin of valve to posterodorsal end of alate rib (see dorsal view in Figure 94). Most processes with 1 or 2 long bristles; additional long bristles along valve edge medial to marginal processes along anterior and ventral margin; a few long bristles scattered over valve surface, but very sparse; surface of valves smooth, without visible punctae, and without gelatinous coating. Minute pustules visible on some processes at very high magnification (Plate 29a).

Infold (Figure 95a; Plates 29d–f, 30): Infold just below middle of anterior margin with usual small bristle near inner edge. Infold of caudal process with about 8 bristles (Figure 95a; Plates 29d–f, 30a,c,d); a few additional bristles present on infold posterior and anterior to caudal process (Figure 95a, Plate 30e,f); posterior infold with 2 setal bristles dorsal to middle (Plate 30b).

Selvage: Selvage with wide lamellar prolongation with smooth edge present along anterior, ventral, and posterior margins; prolongation off caudal process with squarish tip.

Size: USNM 154181 length 1.62 mm, height 1.37 mm; USNM 193106, length 1.80 mm, height 1.52 mm.

First Antenna (Figure 95b): First joint about same length as combined lengths of joints 2–5, with minute medial spines forming rows near ventral margin. Second joint with spinous dorsal bristle. Third and fourth joints fused; third joint with 1 long spinous dorsal bristle and 1 short, bare, ventral bristle; fourth joint with 3 bristles (1 dorsal, 2 ventral). Sensory bristle of long fifth joint with 1 small proximal filament and spine at tip. Medial bristle of minute sixth joint short, bare. Seventh joint: a-bristle about 3 times length of bristle of sixth joint, spinous; b-bristle about one-third longer than a-bristle, bare except for minute spine at tip; c-bristle same length as sensory bristle of fifth joint, with minute spine at tip. Eighth joint: d- and e-bristles well developed, bare with blunt tips (distal parts broken off on illustrated limb but shown by dashed lines); f-bristle shorter than c-bristle, with spine at tip; g-bristle about same length as c-bristle, with small proximal filament and spine at tip.

Second Antenna (Figure 95c): Protopodite bare. Endopodite single jointed with 2 proximal anterior bristles and small terminal bristle on small mound. Exopodite: elongate first joint with small medial bristle on terminal margin; bristle of second joint long, with about 20 proximal spines on ventral margin and distal natatory hairs on both margins; bristles of joints 2–8 with natatory hairs (bristle of eighth joint with or without few slender ventral spines); ninth joint with 2 bristles (1 short, bare or with few hairs, 1 long with natatory hairs and few ventral spines): joints 4–7 with few minute lateral spines along distal margins.

Mandible (Figure 95d): Coxale endite consisting of stout spine; ventral margin of coxale hirsute. Basale: 6 bristles present near ventral margin; dorsal margin with 1 small midbristle and 2 small terminal bristles. Endopodite: first joint with numerous medial spines and stout ventral claw; second joint with small dorsal bristle and stout ventral claw; end joint with stout terminal claw and 3 small bristles, 2 ventral, 1 dorsal.

Maxilla (Figure 95e): Coxale with short bare bristle on dorsal margin. Exopodite with 3 bristles (1 long, 2 short). A small bristle near base of endite I. Endite I with 6 terminal bristles; endite II with 4 bristles; endite III with 6 bristles. Basale and endopodite typical for genus.

Fifth Limb (Figure 95f): Single endite with 1 short bristle Exopodite: first joint with 2 spinous bristles; remaining joints fused, with total of 9 bristles (interpretation: second joint with 3 bristles; third joint with 3 inner bristles and 1 outer bristle, fourth and fifth joints with total of 2 bristles). Epipodial appendage with 37 bristles.

Sixth Limb (Figure 95g): Single endite with 3 bristles (2 small, 1 long). End joint with 12 or 13 bristles with short marginal spines followed by rather long space and then 2 stout hirsute bristles; the 2 hirsute bristles on posterior projection of joint, but bristles not separated from joint by basal suture.

Seventh Limb (Figure 95h): Four bristles in proximal group, 2 on each side; 6 bristles in terminal group, 3 on each side; each bristle with up to 6 bells. Terminus consisting of opposing combs, each with 3–5 teeth.

Furca (Figure 95i): Each lamella with 5 claws; claw 1 fused to lamella, remaining claws separated from lamella by suture; claws 1–4 with both large and small teeth along posterior margins; several spines on lamella following fifth claw.

Bellonci Organ (Figure 95j): Elongate with rounded tip.

Eyes (Figure 95j): Medial eye lightly pigmented. Lateral eye about same size as medial eye, lightly pigmented, with minute ommatidia (either 5 divided or 10 individual ommatidia, exact condition and number uncertain).

Genitalia: Small sclerotized ring on each side of body anterior to furca.

Posterior of Body: Bare.

Y-Sclerite: Typical for genus.

Eggs: USNM 154181 with 7 eggs in marsupium.

COMPARISONS.—The new species E. elofsoni is closely related to E. nodimarginis (Darby, 1965). A narrow rib extending from the posterior outer corner of the alate rib to the posterior process along the dorsal margin of E. elofsoni was not observed on E. nodimarginis. The primary difference between the 2 species is the presence of fossae in the anteroventral quadrant of the carapace of E. nodimarginis. These were observed in a specimen collected off North Carolina (USNM 193108) as well as in the type-specimens. They cover a greater area than covered by the central adductor muscle attachments. The processes along the posterior shell edge are generally better developed on E. elofsoni.