Philomedes fortax Kornicker 1994

Philomedes fortax

ETYMOLOGY.—From the Latin fortax (carrier, bearer).

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

TYPE LOCALITY.—Slope 46, 42°0.20′S, 148°37.70′E, Tasmania, off Freycinet Peninsula; depth 720 m.

PARATYPES.—None.

DISTRIBUTION.—Slope 46, 720 m.

DESCRIPTION OF ADULT FEMALE (Figures 40, 41).—Carapace oval in lateral view with prominent rostrum (with minute anterior process on inferior corner) and small but distinct posterior protuberance of caudal process (Figure 40a,b,d–f). Lateral surface with abundant short spines and few long bristles, some with stout base; long bristles along anterior and ventral margins including caudal process; a long bristle with stout base on dorsal tip of caudal process (Figure 40a,d,f). Posterior edge of caudal process without digitations.

Infold: Rostral infold with row of about 21 bristles (mostly divided) near dorsal, anterior, and ventral valve margins (Figure 40b); a small bristle posterior to inner end of incisur (Figure 40b). Anteroventral margin with about 11 concentric ridges of which outermost forms list (Figure 40c); row of 13 short spinous bristles near list (Figure 40c). Narrow list at about infold midheight along ventral valve margin and closer to inner margin of infold along posterior valve margin. Ventral infold along middle part of valve bare; posterior of ventral infold plus posterior infold with about 14 groups of 1–4 bristles along list; infold dorsal to caudal process with 4 longer single bristles with bases between list and valve edge (Figure 40e). Infold of caudal process with narrow flange along anterior edge of “pocket” with row of 7 or 8 small bristles (Figure 40e,f).

Selvage: Lamellar prolongation along anterior and ventral edges of rostrum with narrow segments and marginal fringe; prolongation along ventral edge of incisur very broad, segmented, with marginal fringe; long hairs with bases at midwidth of prolongation along anteroventral corner of valve; prolongation along anterior half of ventral margin narrow, becoming broader along posterior half (both halves with marginal fringe); posterior tip of caudal process without lamellar prolongation.

Central Adductor Muscle Attachments (Figure 40a,g,h): Comprising about 25 ovoid attachments (Figure 40g). (In lateral view of valves some muscle attachments give impression of being elongate but are attached actually only at outer end. The erroneous elongate muscle attachments of right side drawn with body of animal inside shell are shown in Figure 40h, whereas the muscles projecting from the left side of body after shell is removed are shown in Figure 40g. The major differences between the 2 illustrations reflect the difficulty in obtaining accurate illustrations of muscle attachments of some myodocopids.)

Carapace Size (length, height in mm): Holotype 1.87, 1.35; height 72% of length.

First Antenna (Figure 40i): 1st joint with very few indistinct medial spines near ventral margin. 2nd joint with rows of medial spines on and near proximal part of dorsal margin, 1 row of medial spines near proximal part of ventral margin, several distal rows of lateral spines near ventral margin, 1 distal row of lateral spines near dorsal corner, and 3 bristles (1 ventral, 1 dorsal, 1 lateral) with long proximal and short distal spines (surface spines of 2nd joint not shown). 3rd joint with 5 bristles (1 ventral, 4 dorsal) with bases on medial surface and with short marginal spines. 4th joint with 5 bristles (4 ventral, 1 dorsal) with long proximal and short distal spines. Sensory bristle of 5th joint with 4 short slender proximal and 4 terminal filaments. Medial bristle of 6th joint with long proximal and short distal spines. 7th joint: a-bristle longer than bristle of 6th joint, with long proximal and short distal spines; b-bristle about twice length of a-bristle, with 1 short proximal and 5 terminal filaments; c-bristle with 5 short proximal and 5 longer terminal filaments. 8th joint: d- and e-bristles long bare with blunt tips; f-bristle with 4 short proximal and 5 longer terminal filaments; g-bristle with 3 short proximal and 5 longer terminal filaments; all bristles either of similar length or subequal.

Second Antenna: Protopodite bare. Endopodite 2-jointed: 1st joint with 6 bare bristles (right limb of holotype with 5 proximal, 1 distal (Figure 41b); left limb with bristles together (Figure 41a)); 2nd joint with 2 ventral bristles (proximal with long proximal and short distal spines; distal shorter with few indistinct marginal spines) and 1 recurved bare terminal bristle. Exopodite: 1st joint with minute straight tubular medial bristle; bristles of joints 2–5 fairly short, bare, with pointed tips; bristles of joints 6–8 broken near base on both limbs of holotype (stumps with natatory hairs); 9th joint with 4 long terminal bristles (broken off on both limbs of holotype (stumps with natatory hairs)), 1 short medial bristle with long proximal and short distal spines, and 1 smaller medial bristle with short marginal spines. Joints 4–8 with small basal spines (spines of joints 2 and 3 not seen with certainty); basal spine of 8th joint about length of 9th joint; joints 2–8 with row of slender spines along distal edge. (Broken bristles on exopodite suggest that the ovigerous female is unable to swim, but could be sampling artifact.)

Mandible (Figure 41c): Coxale endite bifurcate, spinous, with small ringed bristle near base; coxale with rows of medial spines near endite (not shown). Basale: dorsal margin with spines, 3 bristles distal to midlength (proximal bristle on right limb of holotype with long proximal spines, otherwise bristles bare) and 2 terminal (medial with long proximal and short distal spines; lateral about half length of medial, bare); ventral margin with 7 bristles (1 proximal and 2 distal with bases on medial side or on margin; 4 with bases on lateral side) with long proximal and short distal spines; medial surface with 6 proximal bristles (3 stout unringed pectinate, 3 slender ringed spinous) and rows of long spines. Exopodite about length of dorsal margin of 1st endopodial joint, with small distal spines, minute spinous terminal process, and 2 distal bristles (proximal longer, with long proximal and short distal spines; distal with only short spines). 1st endopodial joint: ventral margin with 4 bristles (3 long, 1 short (1 of 3 long bristles missing (broken off?) on illustrated left limb of holotype and only proximal part of 2 bristles shown) with long spines (not shown); medial surface with spines at dorsal margin. 2nd endopodial joint: ventral margin with 6 distal bristles forming 2 groups, each with 3 spinous bristles; dorsal margin with 8–10 bristles forming 2 groups (proximal group with 3–5 short bristles (bare or with short spines), distal group with 5 long bristles with long proximal and short distal spines); medial surface with rows of spines. 3rd endopodial joint with 3 claws and 4 bristles (1 of the latter (lateral) obscured on holotype and not seen with certainty).

Maxilla (Figure 41 d): Endite I broad with 10 spinous and pectinate bristles; endite II narrow with 6 spinous and pectinate bristles; endite III long, narrow, with 1 proximal bristle (with short indistinct marginal spines) and 10 distal spinous and pectinate bristles (endite bristles not shown). Precoxale and coxale with dorsal fringe of long hairs; coxale with plumose dorsal bristle. Basale with 4 distal bristles: 2 paired dorsal (these appear as dashed medial lines on illustrated compressed right limb of holotype), and 2 long ventral (1 lateral, 1 medial). Exopodite with 3 bristles (1 short bare and slightly proximal, 2 long terminal with wreaths of long hairs and short distal spines). 1st endopodial joint with long spinous alpha-bristle; beta-bristles obscured on holotype. 2nd endopodial joint obscured but with 3 stout unringed claw-like bristles and several ringed bristles. (Endopodial bristles not shown.)

Fifth Limb: Endite I with 5 spinous bristles; endite II with about 8 spinous bristles; endite III with about 9 bristles (including 2 or 3 claw-like). 1st exopodial joint with 4 pectinate teeth (distal tooth bifurcate with large smooth anterior cusp (Figure 41f) and stout square-tipped pectinate posterior cusp) (Figure 41e); bristle proximal to teeth with short marginal spines; anterior side of joint with 2 spinous bristles at midwidth, and on outer corner a small lobe with a short stout spinous bristle; small spinous flap near lobe (Figure 41f). 2nd exopodial joint (Figure 41 e,f): inner curvature of large flat triangular tooth without nodes but uneven, suggesting that nodes may have broken off; posterior of joint with group of 3 bristles (long bristle with small bristle on each side) (Figure 41e); c-bristle stout with few distal teeth; outer corner of large tooth without small bristle. 3rd exopodial joint with 3 bristles on inner lobe and 2 bristles with long spines on outer lobe. 4th and 5th exopodial joints fused, hirsute, with 6 spinous and pectinate bristles (Figure 41e).

Sixth Limb (Figure 41g): Epipodite represented by 3 small hirsute bristles. Endite I small (medial to endite II on both limbs of holotype) with 3 spinous bristles (2 medial, 1 terminal); endite II small, with 1 medial and 2 or 3 terminal spinous bristles; endite III long, with 1 medial and 7 terminal spinous bristles; endite IV long, with 1 medial and 8 spinous terminal bristles. End joint with 27–31 spinous bristles. (Spines and hairs of bristles not shown.)

Seventh Limb (Figures 40k,l, 41h): With 9 bristles: proximal group with 4 bristles, 2 on each side, each with 3 or 4 bells; terminal group with 3 bristles on peg side, each with 3 or 4 bells, and 2 bristles on comb side, each with 4 bells; all bristles with distal marginal spines proximal to bells. Comb with 16 teeth, each with central part with rounded tip and alar projection on each side. Pegs opposite comb somewhat obscured on both limbs of holotype, with about 14 pegs (1 about twice length of others; remaining pegs elongate but some shorter than others).

Furca (Figure 40j): Each lamella with 10 claws decreasing in length along lamella; claws 1–8 or 9 with long spines forming medial row near base (not all shown); claw 1 of right lamella anterior to claw 1 of left lamella by width of claw base; claw 1 with lateral and medial row of teeth (distal medial teeth larger) and claws 2–10 with single row near posterior edge (teeth on claws 8–10 minute); claws 8–10 with minute spines along anterior edge; few hairs observed on lamella between claws 8–10 and following claws, but hairs absent between claws 1–7.

Bellonci Organ (Figure 41i): Elongate with distinct suture at midlength and rounded tip.

Eyes: Lateral eyes absent. Medial eye with brown elliptical area (stippled in Figure 41i).

Upper Lip (Figure 41i,j): Hirsute with several minute glandular processes at tip.

Anterior of Body (Figure 41i,j): Rounded anterior process between medial eye and upper lip.

Posterior of Body: With few hairs near furca, otherwise bare.

Y-Sclerite (Figure 41k): Typical for genus.

Number of Eggs: Holotype with 16 eggs in marsupium (some eggs shown in Figure 40a). Length of typical egg 0.34 mm.

COMPARISONS.—Species of Philomedes with many terminal pegs on the 7th limb may be divided into those with long pegs (pegs 3 or 4 times width) and those with short pegs. I consider the pegs on the 7th limb of P. fortax to be the former but recognize that some are shorter than usual. In the key to species of Philomedes with long pegs on the 7th limb presented in Kornicker (1987:877), P. fortax keys out to P. lilljeborgii (Sars, 1865). The carapace of P. fortax differs from that species in being smaller (1.87 mm compared to 1.99–2.6 mm (Kornicker, 1987:884)); the 7th limb differs in having 1 peg about twice the length of others rather than all being the same length. The 2nd joint of the endopodite of the female 2nd antenna of P. fortax bears 2 ventral bristles, whereas P. lilljeborgii usually has 3 or 4, rarely 2 (Kornicker, 1987:883). The female P. fortax is without lateral eyes whereas P. lilljeborgii has minute lateral eyes. Philomedes fortax differs from P. horikoshii Hiruta, 1987, in being smaller (1.87 mm compared to 2.20 mm) and in having fewer proximal bristles on the 7th limb (4 compared to 11).