Spinacopia crux Kornicker 1995

Spinacopia crux

ETYMOLOGY.—From the Latin crux (cross).

HOLOTYPE.—Ovigerous female on slide and in alcohol in the Museum of Victoria.

TYPE LOCALITY.—Slope 1, 34°59.52′S, 151°5.94′E, New South Wales, off Nowra, depth 204 m.

PARATYPES.—None.

DISTRIBUTION.—Slope 1, 204 m.

DESCRIPTION OF ADULT FEMALE (Figures 31, 32).—Carapace oval in lateral view with greatest height near midlength (Figure 31a); carapace with broadly rounded posterior in dorsal view (Figure 31b); anterior margin with minute indentation marking incisur; small caudal process with broadly rounded tip; valves with narrow lateral overlap along anterior and ventral margins. Surface without gel-like coating.

Ornamentation: Carapace of holotype decalcified, with dimly visible small fossae and closely packed minute pustules, the latter more apparent along valve margins (Figure 31c). Long undivided bristles, most with broad triangular basal part, very sparsely distributed on lateral surface of valves, also very few small divided bristles; long and short undivided bristles (stouter in proximal half) fairly numerous along valve margins (Figure 31c).

Infold: Anteroventral infold with small bristle near inner margin (Figure 31c). Infold of caudal process with row of 8 spinous bristles on ridge anterior to pocket; 6 small bristles in 3 groups along inner margin of infold (5 bristles anterior to caudal process (Figure 31d), and 1 dorsal to caudal process at about valve midheight measured from dorsal margin (not shown)).

Selvage: Broad lamellar prolongation with smooth outer edge along anterior and ventral margins, narrower along posterior margin dorsal to caudal process, and very narrow along posterior edge of caudal process; prolongation not divided at anterior indentation marking incisur.

Central Adductor Muscle Attachments (Figure 31a): Comprising about 20 small, mostly oval, individual attachments.

Carapace Size (length, height in mm): USNM 193927, 1.10, 0.95.

First Antenna (Figure 31e): 1st joint bare. 2nd joint with spines on ventral and dorsal margins and on lateral side near ventral margin, and 1 spinous dorsal bristle. 3rd and 4th joints fused; small 3rd joint with 2 long spinous bristles (1 ventral, 1 dorsal); long 4th joint with ventral and dorsal spines and 2 long spinous bristles (1 ventral, 1 dorsal). Long 5th joint with few dorsal spines and long ventral bristle, bare except for spine at tip. 6th joint fused to 5th, minute, with small spinous medial bristle. 7th joint: a-bristle about length of bristle of 5th joint, with indistinct spines; b-bristle slightly longer than a-bristle, bare; c-bristle slightly longer than bristle of 5th joint, bare except for spine at tip. 8th joint: d- and e-bristles longer than b-bristle, bare with blunt tips; f-bristle very slightly longer than e-bristle, bare except for spine at tip; g-bristle about same length as bristle of 5th joint, bare except for spine at tip. Marginal spines on bristles of joints 2–4 and 6 indistinct, but visible at high magnification (×15 ocular, ×100 objective).

Second Antenna: Protopodite with long lateral and medial spines along ventral margin near endopodite (Figure 32a). Endopodite 2-jointed (Figure 32a): 1st joint with rows of short medial spines and 2 small proximal bristles (bare or with few indistinct spines); 2nd joint small with long spinous terminal bristle. Exopodite: joint 1 with small recurved medial terminal bristle; bristles of joints 2–8 with stout proximal ventral spines and distal natatory hairs; 9th joint with 3 bristles (ventral long with small proximal ventral spines and distal natatory hairs, middle short with small marginal spines; dorsal short bare and with base medial to middle bristle); joint 2 with single medial spine; joints 3–8 with row of minute spines along distal edges.

Mandible (Figure 32b): Coxale endite with 2 stout terminal spines (with small marginal spines) and long slender proximal spines. Ventral margin of coxale with long spines (distal spines longer). Basale: dorsal margin with small unringed spine-like bristle near midlength and 2 bristles (longer ringed spinous) subterminal; medial surface with 5 bristles including 1 very long bristle and 1 small bristle near ventral margin; lateral surface with 2 or 3 small ringed bristles near ventral margin, and minute unringed bristle or spine on distal edge near dorsal margin (?exopodite). 1st endopodial joint: dorsal margin with several slender terminal spines; ventral margin with several minute spines, 2 or 3 stout spines, and long slender terminal claw with minute proximal spines on dorsal edge; medial surface with slender spines near ventral margin, row of slender spines on distal edge near dorsal margin, and 1 small unringed spine-like bristle at base of ventral claw. 2nd endopodial joint: dorsal margin with 2 fairly long unringed spine-like subterminal bristles; ventral margin with slender spines and long terminal claw; medial surface with small spines near ventral margin and row of indistinct spines along distal edge. 3rd endopodial joint with long terminal claw, 2 short unringed ventral bristles, and 1 minute subterminal unringed dorsal bristle.

Maxilla (Figure 32c,d): Coxale with short dorsal bristle with small indistinct spines. Endite I with 6 bristles; endite II with 4 or 5 bristles; endite III with 6 or 7 bristles. Basale with 1 bristle near exopodite (not shown). Exopodite small with 2 bristles (1 very long and 1 about half its length). 1st endopodial joint with spines along anterior margin, 1 spinous alpha-bristle and 1 spinous beta-bristle. 2nd endopodial joint with 2 lateral spinous a-bristles, 1 medial spinous c-bristle, and 5 pectinate end bristles (anterior bristle ringed distally; middle bristle shortest).

Fifth Limb (Figure 32e): Single endite with 1 long spinous bristle. Exopodite: 1st joint with 3 spinous bristles; 2nd joint with 6 spinous bristles; 3rd joint with 3 spinous bristles on inner and 1 long spinous bristle on outer lobe; fused 4th and 5th joints with 2 spinous bristles; limb hirsute (not all hairs shown). All bristles ringed (not shown). (An alternate interpretation of joints 2–5 is 2nd joint and inner lobe of 3rd joint fused, with 4 bristles on 2nd joint and 2 on inner lobe of 3rd joint (1 on outer lobe), 3 bristles on 4th joint, and 2 on 5th joint.)

Sixth Limb (Figure 32f): Endite I with 2 short spinous bristles; endite II with 2 long spinous bristles. End joint with 12–14 spinous bristles followed by 2 plumose posterior bristles. (An alternative interpretation is that the anterior part of the end joint includes poorly defined endites III and IV (endite III with 2 bristles, endite IV with 2 or 3 bristles.)

Seventh Limb: Proximal group with 2 bristles on same segment (segment 7 or 8 counting from segment proximal to terminus), 1 on each side, each with 3 or 4 bells; terminal group with 6 bristles, 3 on each side, each with 2–4 bells. Terminus with opposing combs each with 2 or 3 weak elongate teeth (Figure 32g).

Furca (Figure 31f): Each lamella with 6 claws; claw 1 nonarticulated; claw 3 about length of claw 4; claws 1 and 2 with medial and lateral teeth along posterior edges, a few teeth slightly longer and stouter than others; claw 4 with teeth along posterior edge (proximal teeth longer); claw 5 with few proximal teeth along posterior edge; teeth not observed on claws 3 and 6; claw 1 with few indistinct hairs or spines along anterior edge; right lamella anterior to left by about width of base of claw 1, and with small spines along anterior edge. Teeth of claws not shown.

Bellonci Organ (Figure 31e): Elongate with 2 sutures at midlength and minute tooth at tip.

Eyes (Figure 31e): Lateral eye small with 4 small amber-colored ommatidia. Medial eye larger than lateral eye, bare, with brown pigment.

Upper Lip (Figure 31g,h): Single hirsute lobe without anterior spines.

Genitalia (Figure 32h): A cup-like spermatophore attached to oval genitalia on each side of body anterior to furca.

Posterior of Body: Evenly rounded, bare.

Y-Sclerite: With ventral branch.

Number of Eggs: USNM 193927 with 5 fairly round eggs; length of 1 egg 0.25 mm; location of 2 eggs in carapace shown in Figure 31a, and 5 eggs in Figure 31b.

COMPARISONS.—The carapace of S. crux is smaller (length 1.10 mm) than those of previously described species of the genus (length 1.17–2.70 mm). The tip of the caudal process of S. crux is more broadly rounded than that of other species of the genus, and the carapaces of other species have abundant surface bristles, whereas, S. crux has very few. The 1st endopodial joint of the mandible of the female S. crux bears 2 or 3 stout ventral spines absent on previously described species. Each lamella of the furca of S. crux bears 6 claws compared to 7 or 8 on previously described species, but the variability of this character on S. crux is unknown.