Pseudophilomedes tetrathrix Kornicker & Caraion 1977

Pseudophilomedes tetrathrix

HOLOTYPE.—USNM 156603, ovigerous female, length 1.10 mm, appendages on slides and in alcohol.

TYPE-LOCALITY.—Cornide de Saavedra station A8a, sample 15.

ETYMOLOGY.—The specific name tetrathrix from the Greek tetra (four) and thrix (hair) refers to the 4 proximal bristles on the 7th limb of the adult female.

PARATYPES.—USNM 156604, 156676, 2 adult females from same sample as holotype; “Grigore Antipa” 463, 1 ovigerous female from station X042; USNM 156677, 1 A-1 male from same sample as holotype.

DESCRIPTION OF ADULT FEMALE (Figures 49, 50; Plates 26–28).—Carapace with straight hinge line, greatest height at middle, small caudal process, overhanging rostrum (Figure 49).

Ornamentation: Surface with shallow fossae (Figure 49; Plates 26a–d,f, 27a,b, 28a,e); single hairs forming row along edges of valves and scattered over valve surface (Plates 26, 27a,b, 28c); 2 low horizontal ribs present (1 above and 1 below central muscle attachment scars) (Figure 49), ribs not visible on all specimens; minute round fossae with pore in middle form clusters between larger fossae (Plate 27d–f); minute pustules with central pore present between and on floor of fossae (Plates 27b, 28).

Infold: Broad in area of rostrum and caudal process, narrower elsewhere; infold behind rostrum with 4 long spinous bristles forming row parallel to edge of rostrum (Figure 50a); infold immediately ventral to incisur with 1 short bristle; infold in front of caudal process with 5 spinous bristles near top of list (Figure 50b).

Selvage: Wide fringed lamellar prolongation present along anterior, ventral and posterior margins of each valve; prolongation divided at inner corner of incisur (Plate 26d,e).

Central Muscle Attachment Scars: Consisting of about 18 widely dispersed individual ovoid scars (Figure 49; Plates 26a, 27a).

Size: USNM 156603, length 1.10 mm, height 0.67 mm; USNM 156604, length 1.06 mm, height 0.64 mm; “Grigore Antipa” 463, length 1.17 mm, height 0.62 mm; USNM 156676, length 1.08 mm, height 0.64 mm (Figure 35).

First Antenna (Figure 50c): 2nd joint: spines along ventral and dorsal margin and with 1 dorsal bristle. 3rd joint: 2 bristles (1 ventral, 1 dorsal). 4th joint: 3 bristles (2 ventral, 1 dorsal). 5th joint: sensory bristle with 2 proximal and 2 distal filaments. 6th joint: minute, medial bristle short. 7th joint: a-bristle about twice length of bristles of 6th joint; b-bristle slightly longer than a-bristle, with bifurcate tip; c-bristle about same length as sensory bristle of 5th joint, with 4 marginal filaments and bifurcate tip. 8th joint: d- and e-bristles bare, length about same as c-bristle; f- and g-bristles about same length as c-bristle, with 5 marginal filaments and bifurcate tip.

Second Antenna (Figure 50d): Protopodite: bare. Endopodite single-jointed with 1 short bare proximal anterior bristle and 1 longer terminal bristle with short marginal spines. Exopodite: terminal margin of 1st joint with short recurved medial spine; distal margins of joints 2–8 with spines forming row; bristle of 2nd joint reaching just past 9th joint, with about 10 stout marginal spines becoming more slender towards tip of bristle, followed by slender hairlike spines near tip; bristles of joints 3–8 relatively short, with stout ventral spines and knifelike tip, no natatory hairs; 9th joint with 2 short bristles, longer of these with stout ventral spines, other with short marginal spines.

Mandible (Figure 50e): Coxale endite with bifurcate spinous tip. Basale: dorsal margin with 3 bristles (1 distal to middle, 2 terminal); medial surface spinous, with 2 short bristles (1 proximal, 1 near middle), both with short marginal spines; 1 long distal bristle with long proximal and short distal spines present near ventral margin, but with base on medial side; 2 minute bristles present on ventral margin distal to middle. Exopodite spinous with 2 terminal bristles, outer bristle slightly shorter than inner. Endopodite: 1st joint with 3 ventral bristles (1 of these very small), medial surface of joint spinous distally; 2nd joint with medial surface with few spines, dorsal margin with 1 proximal bristle and 3 near middle, ventral margin with 3 subterminal bristles; end joint with 1 long claw, 1 long lateral bristle reaching past middle of claw, 1 short claw with base on medial edge of joint near middle, and 2 short bristles (1 ventral and 1 dorsal to short claw).

Maxilla (Figure 50f): Precoxale and coxale with dorsal fringe of hairs; coxale with hirsute dorsal bristle. Endite I with 5 bristles including 3 short, stout, pectinate, terminal bristles; endite II with 4 bristles including 2 short, stout, pectinate, terminal bristles; endite III about half length of endites I and II, with 3 bristles (2 short and 1 long). Exopodite consisting of 3 bristles on lateral side of 1st endopodite joint near basale. Basale hirsute with 2–3 slender bristles along distal margin (1 or 2 ventral, 1 lateral near dorsal margin). Endopodite: 1st joint with 1 long, stout, spinous, terminal bristle on anterior margin; end joint with 3 bristles (2 long, 1 short; inner of long bristles shorter but slightly stouter than outer bristle, both with marginal spines).

Fifth Limb (Figure 50g): Single endite present with 1 short bristle. Exopodite: 1st joint with large proximal tooth with 3 prongs and 2 bristles, large distal tooth consisting of 4 prongs, and 1 short proximal bristle; 2nd joint with large fanglike tooth, inner edge of fanglike tooth with single short distal tooth followed by 2 3-pronged teeth, posterior side of joint with 2 bristles (1 short, 1 long); 3rd joint with 2 hirsute bristles on outer lobe and 1 bare bristle on inner lobe; 4th and 5th joints fused, hirsute, with 4 spinous bristles.

Sixth Limb (Figure 50h): Endite I with 3 short hirsute bristles; endite II with 2 longer bristles (1 with short marginal spines, other with long proximal hairs); endite III with 5 bristles with short or long spines; endite IV with 4 bristles with short or long spines; end joint with 7 bristles (posterior 2 hirsute, remaining bristles with long proximal and short distal spines); 1 short bristle in place of epipodial appendage.

Seventh Limb (Figure 50i): 6 bristles in distal group (3 on each side), 4 bristles in proximal group (2 on each side), each bristle with 3–6 bells and few distal marginal spines; terminus consisting of opposing combs, one comb with 5 alate teeth, other with 3 spinous teeth.

Furca (Figure 50J): Each lamella with 6 claws; claw 4 much stouter and slightly longer than claw 3; claw 1 with large tooth medially near middle and about 9 stout teeth proximally along posterior margin, these increasing in length distally along margin and followed by thinner teeth; claws 2 and 4 with slender teeth along posterior margin; claws 3, 5, and 6 with a few proximal, slender teeth along anterior margin and more teeth along posterior margin; hairs on margin of lamella posterior to claws.

Rod-shaped Organ: Elongate, about 6 short segments in middle part; tip rounded, possibly with minute terminal spine (Figure 50k,l).

Eyes: Medial eye bare, with reddish pigment (Figure 50k,l); lateral eye small with 4–6 minute yellow ommatidia (Figure 50m).

Upper Lip: Helmet-shaped (Figure 50l).

Eggs: USNM 156603 with 6 eggs; USNM 156604 with 3 eggs; USNM 156675 with 1 egg.

DESCRIPTION OF A-1 MALE (Figure 51).—Carapace similar in outline to that of adult female (Figure 51a); surface with distinct shallow fossae, some larger than others.

Infold: Rostral infold with 4 spinous bristles; infold of caudal process with 4–5 spinous bristles forming row at top of list; anteroventral infold with 1 short bristle below incisur.

Size: USNM 156677, length 0.93 mm, height 0.51 mm.

First Antenna: Not examined in detail but similar to that of adult female.

Second Antenna: Endopodite 3-jointed (Figure 51b): 1st joint short with 2 short anterior bristles; 2nd joint elongate with 2 bare ventral bristles; 3rd joint elongate with 2 short terminal bristles. Exopodite: bristle of 2nd joint just reaching past 9th joint, with few slender ventral spines; bristles of joints 3–8 not more than about one-third longer than bristle of 2nd joint, with stout ventral spines, no natatory hairs; 9th joint with 3 bristles, all shorter than bristle of 2nd joint, ventral of these with stout ventral spines, middle bristle with few slender spines or bare, dorsal bristle very short, bare.

Mandible, Maxilla, 5th Limb: Not examined in detail but, in general, similar to limbs of female.

Sixth Limb: Same as that of adult female except end joint with 6 bristles, posterior 2 hirsute, others spinous.

Seventh Limb (Figure 51c): 4 bristles in distal group (2 on each side), each bristle with 4 bells; no proximal bristles; terminus with opposing combs with 3 alate teeth in one, and 1 spinous tooth in other.

Furca: Each lamella with 6 claws similar to those of adult female.

Rod-shaped Organ: Similar to that of adult female.

Eyes: Lateral eyes small, unpigmented, with about 12 minute yellowish ommatidia (Figure 51d); medial eye similar to that of adult male and female.

Copulatory Organ: Not observed.

COMPARISONS.—The new species P. tetrathrix differs from P. foveolatus in having 4 instead of 3 endites on the 6th limb, and 4 instead of 2 proximal bristles on the 7th limb of the adult female. P. tetrathrix differs from P. angulatus in not having prominent horizontal ribs on the carapace and in being smaller. P. tetrathrix differs from P. thalassa in having 4 instead of 9–10 bristles on the rostral infold and in being much smaller.