Pseudophilomedes thalassa Kornicker & Caraion 1977

Pseudophilomedes thalassa

HOLOTYPE.—“Grigore Antipa” 290, adult female, length 1.68 mm, appendages and valves in alcohol.

TYPE-LOCALITY.—Thalassa station X048.

ETYMOLOGY.—The species named for the research vessel Thalassa.

ALLOTYPE.—USNM 154190, adult male from station X072.

PARATYPES.—USNM 150104, 154188, 154189, 156– 602, 4 ovigerous females from station X048; USNM 156609, adult female from station X048; USNM 156– 605, 1 adult male from station A8a; USNM 156678, 3 specimens from station X048; USNM 156680, 1 adult male from station X048; USNM 156681, 1 A-1 male from station X048.

DESCRIPTION OF FEMALE (Figures 41–44; Plates 24, 25).—Carapace with straight hinge line, greatest height in front of middle, incisur forming right angle, small caudal process (Figures 41, 42; Plate 24b–d).

Ornamentation: Surface with shallow fossae, (Plate 24e,f), single hairs forming row along edges of valves and scattered over valve surface (Plate 24b,f); minute nodes present in posterodorsal part of each valve (Figures 41, 42; Plate 24a,d).

Infold: Broad in area of rostrum and caudal process, narrower elsewhere (Plate 25a–c); infold behind rostrum with 9 or 10 long spinous bristles forming row parallel to edge of rostrum (Figure 43a, Plate 25c); infold immediately ventral to rostrum with 1 short bristle; infold in front of caudal process with 6 spinous bristles near top of list (Figure 45b); anteroventral infold with about 3 ridges paralleling valve margin (Plate 25a).

Selvage: Wide fringed lamellar prolongation present along anterior, ventral, and posterior margin of each valve (Plates 24c, 25b); prolongation divided at inner corner of incisur.

Central Muscle Attachment Scars: Consisting of about 35 widely dispersed individual ovoid scars (Figures 41, 42; Plate 25d).

Size: USNM 150104, length 1.63 mm, height 1.06 mm; height 65 percent of length; USNM 154188, length 1.58 mm, height 1.04 mm; height 66 percent of length; USNM 154189, length 1.72 mm, height 1.08 mm, height 63 percent of length; USNM 156602, length 1.70 mm, height 1.06 mm, height 62 percent of length; USNM 156609, length 1.71 mm, height 1.07 mm, height 63 percent of length; holotype, length 1.68 mm, height 1.04 mm, height 62 percent of length (Figure 35).

First Antenna (Figure 43c): 2nd joint: 1 dorsal bristle with short marginal spines, short spines along dorsal margin, and long proximal hairs on medial surface near ventral margin. 3rd joint: 2 bristles with short marginal spines, each about twice length of bristle on 1st joint. 4th joint: 1 dorsal bristle (with short marginal spines) almost reaching distal end of 6th joint, and 2 ventral bristles (with medium length proximal spines and short distal spines) reaching well past end of stem. 5th joint: long, with sensory bristle with 2 short proximal filaments, 1 short distal filament, and bifurcate tip. 6th joint: short, medial bristle short, with short marginal spines. 7th joint: a-bristle 2 to 3 times length of bristle of 6th joint, with short marginal spines; b-bristle 3 to 4 times length of bristle of 6th joint, with bifurcate tip; c-bristle about same length as sensory bristle, with 4 short marginal filaments and bifurcate tip. 8th joint: d- and e-bristles bare with truncate tip; length about same as sensory bristle; f-bristle with 3 proximal marginal filaments, 1 double distal filament, and bifurcate tip; g-bristle with I proximal filament, 1 distal filament, and bifurcate tip; f- and g-bristles about same size as sensory bristle.

Second Antenna: Protopodite bare. Endopodite single-jointed, with 2 short bare proximal anterior bristles and 1 longer terminal bristle with long proximal and short distal spines (Figure 43d,e). Exopodite: terminal margin of 1st joint with 1 short recurved medial spine; distal margins of joints 2–8 with faint spines forming row; bristle of 2nd joint very long, about one and one-half times length of stem joints 1–9, with 18 stout proximal spines along ventral margin and natatory hairs distally; bristles of joints 3–8 with distal natatory hairs and stout proximal spines along ventral margin; 9th joint with 3 bristles (ventral bristles long, with stout, proximal, ventral spines and distal natatory hairs; middle bristle shorter, with slender, proximal, ventral spines and distal natatory hairs; dorsal bristle short with very short marginal hairs or spines).

Mandible (Figure 43f): Coxale endite with bifurcate tip, each with strong terminal spine or tooth and smaller marginal spines (distal prong with 5 marginal spines; proximal prong with about 25 marginal spines, some very small). Basale: dorsal margin with 3 bristles (1 distal to middle, 2 terminal); medial surface near ventral margin with 2 or 3 short spinous bristles and 1 longer spinous terminal bristle. Exopodite spinous, with 2 terminal bristles, outer bristle slightly shorter than inner. Endopodite: 1st joint with 3 ventral bristles (inner medial bristle with long proximal and short distal spines, remaining bristles shorter and with short marginal spines); 2nd joint with ventral and medial spines, dorsal margin with 1 proximal bristle and 4 near middle, ventral margin with 3 subterminal bristles (1 proximal, 2 distal); end joint with 1 long claw with base on lateral side of joint edge, 1 short claw with base on medial edge of joint near ventral margin, 1 minute claw with base on medial edge of joint near dorsal margin, and 3 annulate bristles, longest of these lateral and just reaching past middle of long claw.

Maxilla (Figure 43g–j): Precoxale and coxale with dorsal fringe of hairs; coxale with long hirsute dorsal bristle. Endite I with 1 long spinous bristle, 1 short spinous proximal bristle, and 3 short stout pectinate terminal bristles; endite II with 2 short stout pectinate terminal bristles and 2 short slender proximal spinous bristles; endite III about half length of endite II, with 2 short slender proximal bristles and 2 longer spinous terminal bristles. Exopodite consisting of short lobe with 3 bristles (2 long, 1 short) with short marginal spines. Basale hirsute with 3 slender bristles along distal margin. Endopodite: 1st joint with 1 slender distal bristle on anterior margin and 1 longer, stouter, spinous terminal bristle; end joint with 5 bristles (3 short, 2 long; inner of long bristles shorter but slightly stouter than outer bristle, both with marginal spines).

Fifth Limb (Figure 44a–j): Single endite present with 1 short bristle. Exopodite: 1st joint with large proximal tooth consisting of 3 prongs and 3 or 4 bristles, large distal tooth consisting of 4 prongs, and a single short bristle distal to endite bristle present on anterior side of 1st joint (possibly 2nd endite?); 2nd joint with large fanglike tooth (inner edge of fanglike tooth with single short distal tooth) followed by tooth with 3 large prongs and 1 short prong and by proximal tooth with 3 prongs, posterior side of 2nd joint with 2 bristles (1 short slender, 1 long, stout); 3rd joint with 2 slender bristles on outer lobe and 1 on inner lobe; 4th and 5th joints fused, with 4 bristles.

Sixth Limb (Figure 44k,l): Endite I with 3 spinous bristles (1 long, 2 short); endite II with 1 long spinous bristle; endite III with 5 spinous bristles; endite IV with 4 spinous bristles; end joint with 9 bristles, posterior 2 of these hirsute, remaining spinous; 1 bristle with short faint marginal spines present in place of epipodial appendage; surface of appendage hirsute.

Seventh Limb (Figure 44m,n): 6 bristles in distal group (3 on each side), 4 bristles in proximal group (2 on each side), each bristle with 3–7 bells and few marginal distal spines; terminus consisting of opposing combs with faint teeth without marginal spines, about 9 or 10 on one comb, about 3 or 4 on other.

Furca (Figure 44o,p): Each lamella with 8 or 9 claws (usually 8); claw 4 much stouter and about the same length or longer than claw 3; posterior 4 or 5 claws secondary; claw 1 with large medial tooth near middle and smaller teeth proximally on lateral and medial sides; claws 2 and 4 with small teeth forming medial and lateral rows near concave margin; claw 3 with few faint teeth; claws 5–8 or 5–9 with faint spines along anterior and posterior margins; claws 1 and 2 with faint distal hairs along anterior margins; margin of lamella following claws with 1–4 short spines.

Rod-shaped Organ: Elongate, about 7 short segments in middle part; tip rounded with short terminal spine (Figure 43k,l).

Eyes: Medial eye bare (Figure 43k); lateral eye small with reddish pigment in preserved material, with 3–5 yellow ommatidia (Figure 43k).

Upper Lip: Helmet-shaped (Figure 43k).

Eggs: USNM 150104 with 12 eggs in marsupium; USNM 154188 with 3 eggs.; USNM 154189 with 4 eggs: USNM 156602 with 10 eggs.

Parasites: Holotype with 1 cyproniscid isopod in marsupium; USNM 156609 with 2 cyproniscid isopods and 1 clutch of isopod eggs in marsupium of ostracode.

DESCRIPTION OF ADULT MALE (Figures 45–47).—Carapace with straight hinge line, large overhanging rostrum, broad open incisur, and projecting caudal process (Figures 45, 46, 47a); anterior margin of rostrum with rim and with minute processes.

Ornamentation: Carapace with shallow punctae on well-preserved specimens (Figure 45); posterior of valve with few small nodes (Figure 45); long double hairs present on posterior part of valve; long hairs present along anterior and ventral margin.

Infold: Infold behind rostrum with 8 long bristles forming row parallel to edge of rostrum; infold immediately ventral to incisur with I short bristle; infold in front of caudal process with 6 spinous bristles near top of list.

Selvage: Wide fringed lamellar prolongation along anterior, ventral, and posterior margins.

Size: USNM 154190, length 1.38 mm, height 0.80 mm, height 58 percent of length; USNM 156605, length 1.40 mm, height 0.84 mm, height 60 percent of length; USNM 156680, length 1.40 mm, height 0.88 mm, height 63 percent length (Figure 35).

First Antenna (Figure 47b): 1st joint: bare. 2nd joint: short dorsal bristle with short marginal spines. 3rd joint: short, with 1 dorsal bristle and 1 shorter ventral bristle, both with short marginal spines. 4th joint: long dorsal bristle with short marginal spines. 5th joint: small, triangular, wedged ventrally between 4th and 6th joints; sensory bristle of 5th joint with bulbous base with abundant long filaments and long stem with 4 marginal filaments. 6th joint with medial bristle reaching well past 8th joint. 7th joint: a-bristle almost twice length of bristle of 6th joint; b-bristle almost twice length of a-bristle, with 2 long filaments near middle, and bifurcate tip; c-bristle very long, stout, with 9 short filaments on broken bristle of examined specimen. 8th joint: d- and e-bristles bare, of equal length, reaching well past tip of sensory bristle of 5th joint; f-bristle similar to c-bristle, also broken on specimen examined, with 10 short marginal filaments on stump; g-bristle same length as d- and e-bristles, with 7 marginal filaments and bifurcate tip.

Second Antenna: Protopodite bare. Endopodite 3-jointed (Figure 47c): 1st joint short, with 1 or 2 short proximal anterior bristles; 2nd joint elongate, with 1 bristle proximal to middle; 3rd joint reflexed on 2nd, with 2 short subterminal bristles and ridged tip. Exopodite: 1st joint bare; bristles of joints 2–8 with natatory hairs but without spines; 9th joint with 4 bristles (2 long with natatory hairs, 2 short with short hairs); joints 2–8 with short spines forming row along terminal margin; 9th joint with few spines forming medial row on distal margin; joints 2–9 with minute spine on dorsal corner.

Mandible (Figure 47d): Coxale endite represented by small spine; lateral side of coxale with few spines forming short rows. Basale: medial side with 1 short proximal bristle and 1 short bristle just distal to middle, both closer to ventral margin than to dorsal margin; ventral margin with 1 medium length proximal bristle and 1 long stout distal bristle, both with long proximal and short distal spines; dorsal margin with 1 bristle distal to middle and 2 terminal bristles. Exopodite about one-third length of 1st endopodite joint, with 2 long terminal bristles. Endopodite: medial surface of 1st joint with spines forming rows; ventral margin with 3 terminal bristles (2 long and 1 short), all with marginal spines; 2nd joint with medial and lateral surfaces with spines forming rows, dorsal margin with bristles forming 2 groups proximal to middle (1 bristle in proximal group, 3 in distal group), ventral margin with 3 short subterminal bristles; end joint with 1 long claw with faint spines along ventral margin, 1 bristle reaching past middle of claw, 1 short ventral bristle, 1 short medial bristle, and 1 short clawlike medial bristle dorsal to and shorter than short medial bristle.

Maxilla (Figure 47e): Limb weakly developed, reduced. Precoxale and coxale with fringe of long hairs dorsally; coxale with short, stout, hirsute dorsal bristle. Endite I with 5 bristles; endite II with 4 bristles; endite III short, with 1 proximal and 3 terminal bristles. Exopodite consisting of 3 bristles with bases on 1st endopodite joint near basale. Basale hirsute with 3 bristles along distal margin (2 lateral, 1 medial). Endopodite: 1st joint with hairs on dorsal margin and 2 terminal bristles (1 ventral, 1 dorsal); end joint with 5 bristles.

Fifth Limb (Figure 47f): Epipodial appendage with 48 bristles. Single endite present with 1 short bristle. Exopodite: 1st joint with 3 proximal ringed bristles and 2 small distal finger-formed bristles; 2nd joint with 2 bristles; inner lobe of 3rd joint with 1 bristle, outer lobe with 2 bristles; fused 4th plus 5th joints hirsute, elongate, with 4 bristles.

Sixth Limb (Figure 47g): Endite I with 3 short hirsute bristles; endite II with 2 hirsute bristles; endite III with 3 long hirsute bristles and 2 shorter bristles with short marginal spines; endite IV with 2 hirsute bristles and 2 shorter bristles with marginal spines; end joint with 7 or 8 anterior bristles with long proximal hairs and short distal spines, and 2 long hirsute posterior bristles; limb hirsute; 1 short bristle with short marginal spines present in place of epipodial appendage.

Seventh Limb (Figure 47h): 4 bristles in distal group (2 on each side); USNM 154190 with 1 bristle in proximal group, USNM 156605 without proximal bristle; each bristle with 4–7 bells; terminus bare without combs.

Furca (Figure 47i): Each lamella with 7 or 8 claws; claw 4 much stouter and longer than claw 3; posterior 3 or 4 claws secondary; claw 1 with proximal teeth slightly larger than distal teeth, no large tooth near middle as on claw 1 of female; all claws with lateral and medial row of teeth along posterior margins.

Rod-shaped Organ (Figure 47;): Elongate, with 3 to 5 short segments in middle part; distal end broad, tapering to rounded tip with few terminal spines.

Eyes: Medial eye bare, lightly pigmented (Figure 47j); lateral eye larger than medial eye, with about 19 ommatidia (Figure 47K).

Upper Lip: Helmet-shaped (Figure 47l).

Copulatory Organ: Tip with elongate sclerotized hook and lobe with bristle (Figure 47i).

DESCRIPTION OF A-1 Male (Figure 48).—Carapace similar in outline to that of adult female (Figure 48a). Surface punctae not visible on examined specimen.

Infold: Rostral infold with 9 spinous bristles; infold of caudal process with 5 spinous bristles forming row at top of list; anteroventral infold with 1 short bristle below incisur.

Size: USNM 156681, length 1.24 mm, height 0.77 mm, height 62 percent of length.

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

Second Antenna: Endopodite 3-jointed (Figure 48b): 1st joint short with 1 short anterior bristle; 2nd joint elongate with 2 long bristles, longer of these with long proximal spines; 3rd joint elongate with 2 short terminal bristles. Exopodite: bristles of joints 2–8 with few proximal hairs on dorsal margin, stout proximal spines along ventral margin, and natatory hairs distally; bristles long, similar to those of adult female; 9th joint with 3 bristles (2 long with proximal ventral spines and distal natatory hairs, 1 short with few hairs).

Mandible, Maxilla, 5th and 6th Limbs: Not examined in detail but, in general, similar to limbs of adult female.

Seventh Limb (Figure 48c): 4 tapered bristles in distal group, each with 4–5 bells; 1 tapered proximal bristle with 2 bells; terminus bare, without combs.

Furca: Each lamella with 8 claws similar to those of adult female except claw 3 shorter than claw 4.

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

Eyes: Lateral eyes well developed, with reddish brown pigment and about 16 ommatidia, larger of these ventrally located in eye sac (Figure 48d); medial eye similar to that of adult male and female.

Copulatory Organ: Not observed.

COMPARISONS.—The new species P. thalassa differs from other species of Pseudophilomedes in having more bristles (8–10) on the rostral infold. Other species have only 4–5 bristles on the rostral infold. Each lamella of the adult female furca of P. thalassa bears 8 or 9 claws, whereas the lamellae of P. tetrathrix, new species, P. angulatus Müller, and P. foveolatus Müller, bear only 6 or 7. The carapace of P. thalassa resembles in outline that of Paramekodon inflatus Brady and Norman, 1896. It differs from that species in having 8–10 bristles on the rostral infold instead of only 4 (see Kornicker, 1968:462, for supplementary description of Paramekodon inflatus).