Philomedes hirutai Kornicker 1984

Philomedes hirutai

ETYMOLOGY.—Named for Dr. ShinIchi Hiruta, Hokkaido University, Japan.

HOLOTYPE.—USNM 158252, adult female on slide and in alcohol (unique specimen).

TYPE-LOCALITY.—Upper continental slope off South Carolina, Bureau of Land Management southeast coastal study, sta 0155-2 (2G), depth 218 m.

DISTRIBUTION.—Collected only at the type-locality (Map 1).

DIAGNOSIS.—Anterior margin of rostrum concave; length of adult female 1.79 mm (1 specimen). 2nd joint of 1st antenna of adult female with 3 bristles (1 ventral, 1 dorsal, 1 lateral). 1st endopodial joint of 2nd antenna of adult female with 6 bristles, 2nd joint with 1 spinous ventral bristle and 1 recurved terminal bristle. Dorsal margin of mandibular basale with 1 bristle distal to middle and 2 terminal. 7th limb with 8 proximal bristles (4 on each side) and 5 distal bristles (3 on peg side, 2 on comb side); terminus with comb of about 5 alate teeth opposite 2 pegs (outer peg shorter than inner peg). Each lamella of furca with 10 claws decreasing in length posteriorly along lamella.

DESCRIPTION OF ADULT FEMALE (Figures 10–13).—Carapace oval in lateral view with prominent rostrum having concave distal margin; posterior end forming angle just below valve middle; without caudal process except for slight broadening of infold at posteroventral curvature of valve (Figure 11c–f); anteroventral corner of rostrum with minute process barely extending past edge of rostrum (Figure 11b); posterior margin of valve, ventral to bristle on inner side of valve at posterior angle, minutely pustulose (Figure 11c,e,f); viewed from inside, edge of valve between posterior angle and “caudal process” linear (Figure 11c–f).

Ornamentation: Valve surface with widely distributed short and long bristles, many with broad basal part; bristles more abundant along ventral margin and, also, along posterior margin ventral to posterior angle (Figure 11c,e); weak reticulations visible in transmitted light.

Infold: Infold of rostrum with 17 hairy bristles along posterior and distal margins, and 3 widely spaced bristles along ventral margin (Figure 11b); 1 minute bristle present proximal to ventral part of inner end of incisur (Figure 11b); anteroventral infold with about 11 ridges, the outer of these being the list; anteroventral list with about 10 short, stout, spinous bristles; middle part of ventral infold with narrow list but no bristles; list on posteroventral and posterior infold (to point just dorsal to angle near middle of posterior valve margin) with about 45 small bristles (in groups of 1 to 3 bristles, usually 2); list not present along posterodorsal infold between point just dorsal to posterior valve angle and posterior juncture of ligament; posterodorsal infold with about 10 bristles (many of these longer than those along list, Figure 11c; not all bristles shown in Figure 11c); USNM 158252, in vicinity of “caudal process,” with 1 bristle between list and valve edge on left valve (Figure 11c) but without bristle on right valve (Figure 11d).

Selvage: With broad, fringed, lamella prolongation except along posterior edge of valve dorsal to posteroventral curvature where selvage becomes narrow and bare (Figure 11f); anteroventral selvage with long hairs with bases at proximal edge of lamellar prolongation.

Size: Length 1.79 mm, height 1.23 mm.

First Antenna: (Figure 12a,b): 1st joint with medial and lateral spines. 2nd joint spinous, with 3 equilength bristles (1 ventral, 1 dorsal, 1 lateral). 3rd joint short with 3 or 4 bristles (1 ventral, 2 or 3 dorsal). 4th joint with 5 bristles (1 dorsal, 4 ventral; left limb of USNM 158252 with only 2 ventral bristles considered atypical). Sensory bristle of long 5th joint with 6 short proximal filaments and 5 terminal filaments including stem. Short 6th joint with spinous medial bristle. 7th joint: spinous a-bristle about twice length of bristle of 6th joint; b-bristle about twice length of a-bristle, shorter than sensory bristle of 5th joint, with 4 marginal filaments (1 proximal, 3 subterminal); c-bristle only slightly shorter than sensory bristle, with 5 proximal and 5 terminal filaments including stem. 8th joint: d- and e-bristles bare with blunt tips, about same length as c-bristle; f-bristle longer than b-bristle but shorter than c-bristle, with 8 filaments including stem; g-bristle same length as sensory bristle, with 3 proximal and 5 terminal filaments including stem.

Second Antenna (Figure 12c,d): Protopodite bare. Endopodite 2-jointed: 1st joint with 6 short equilength bristles; 2nd joint elongate, with 1 spinous ventral bristle (shortness of bristle of right limb of USNM 158252 considered atypical, Figure 12c), and 1 recurved terminal bristle. Exopodite: 1st joint with medial hairs forming rows and minute, terminal, medial bristle with tubular tip; bristle of 2nd joint just reaching past distal end of 9th joint, with about 7 faint ventral spines near middle and with spine at tip; bristles of joints 3–5 short, less than twice length of bristle of 2nd joint, bare except for spine at tip; bristles of joints 6–8 long, with natatory hairs, some with few faint ventral spines near middle; 9th joint with 7 bristles (3 long with natatory hairs and few faint spines; 1 medium with natatory hairs; 3 short with numerous small marginal spines, no hairs); joints 2–8 with fairly long hairs forming row along distal margin; joints 3–8 with small basal spines; 9th joint with small lateral spine.

Mandible (Figure 12e): Coxale endite bifurcate, spinous, with minute bristle near base. Basale: dorsal margin with 3 bristles (1 near middle, 2 terminal); medial side with long spines forming rows, 5 proximal ventral bristles (3 unringed and strongly pectinate, 2 ringed, spinous, and weakly pectinate), and 1 additional spinous bristle just distal to the 5 proximal bristles; ventral margin with 2 spinous distal bristles; lateral surface with 5 spinous bristles near ventral margin (proximal bristle especially close to margin). Exopodite hirsute, about three-fourths length of dorsal margin of 1st endopodial joint, with 2 spinous subterminal bristles (distal bristle shorter than other). 1st endopodial joint with short medial spines forming rows and 4 ventral bristles (3 long, 1 short). 2nd endopodial joint: ventral margin with bristles forming 2 distal groups (3 bristles in proximal group, 3 or 4 in other); dorsal margin with bristles forming 2 groups near middle (4 bristles in proximal group, 6 in other); medial surface with long and short spines forming rows. End joint with 3 stout claws with ventral spines (dorsal claw about one-half length of middle claw; ventral claw about three-fourths length of middle claw), and 4 bristles (at least 3 of these with spines).

Maxilla (Figures 12f, 13a): Precoxale and coxale with dorsal fringe; coxale with plumose dorsal bristle. Endite I broad, with 10 spinous bristles; endite II narrow, with 6 spinous bristles; endite III narrow, much longer than endite II, with 1 proximal bristle and about 8 distal bristles. Basale with 3 bristles along distal margin (1 dorsal, 2 ventral). Exopodite with 3 bristles (2 long, spinous; 1 short, bare). 1st endopodial joint with 1 alpha-bristle with long proximal and short, distal, marginal spines, 5 bare beta-bristles (Figure 13a), and hairs along anterior margin. 2nd endopodial joint obscure on specimen examined but with 3 stout pectinate claws (not all shown on illustrated limb) in addition to ringed bristles.

Fifth Limb (Figure 13b): Endite I with about 5 bristles; endites II and III each with about 10 spinous bristles; some bristles of endites claw-like, pectinate, others bristle-like, some with spear-like tips. 1st exopodial joint: main tooth consisting of 3 stout pectinate teeth followed closely by tooth having only 1 small marginal tooth; distal pectinate tooth of main tooth with large bifurcate tooth on anterior side; short spinous bristle present just proximal to proximal tooth of main tooth; 2 anterior bristles present on outer edge of 1st joint proximal to distal tooth of main tooth (not shown on illustrated limb); anterior side of 1st joint with 1 short stout bristle near outer edge (not shown on illustrated limb). 2nd exopodial joint: large tooth with 1 or 2 small bifurcate teeth along inner margin; posterior side with 3 bare a- and b-bristles forming group (long middle bristle and 2 short bristles), and 1 stout proximal c-bristle with distal spines; posterior side of 2nd joint with small spinous d-bristle near outer corner of tooth. Inner lobe of 3rd exopodial joint with 3 spinous and pectinate bristles; outer lobe with 2 subequal bristles with long proximal and short distal spines. Fused 4th and 5th exopodial joints hirsute, with 6 spinous bristles.

Sixth Limb (Figure 13c): Endite I with 3 bristles; endite II with 4 bristles; endite III with 9 bristles; endite IV with 8 or 9 bristles. End joint with 22 or 23 spinous and hirsute bristles; 3 short hirsute bristles present in place of epipodial appendage.

Seventh Limb (Figure 13d): Each limb with 6 bristles on comb side (4 proximal, 2 terminal) and 7 bristles on peg side (4 proximal, 3 terminal); total bristles 13, each bristle with up to 5 bells. Terminus consisting of comb with about 15 alate teeth of similar type but of different lengths; 2 pegs present opposite comb (outer peg about one-third to one-half length of inner recurved peg).

Furca (Figure 13e,f): Each lamella with 10 claws decreasing in length posteriorly along lamella; claw 1 with teeth along posterior edge and also medial row (posterior teeth with smaller tooth between each pair of stout teeth) (Figure 13f); remaining claws with teeth along posterior edge; 6 posterior claws with spines or few teeth along anterior edge; clusters of hairs present medially at bases of claws and on edge of lamella following claws; (teeth and most hairs not shown in Figure 13e); a few small spines present along anterior margin of lamella; claw 1 of right lamella located anterior to that of left lamella.

Bellonci Organ (Figure 13g): Long, slender, with suture near middle, and pointed tip; small ventral subapical spine.

Eyes (Figure 13g): Medial eye with narrow linear zone of brown pigment near middle. Lateral eye not seen with certainty: if present, minute, faint unpigmented, with 5 or 6 minute cells (ommatidia?).

Upper Lip (Figure 13g): Shape typical for genus, with minute anterior processes and abundant hairs.

Genitalia (Figure 13e): Faint oval area on each side of body.

Anterior of Body (Figure 13e): With single sclerotized process between medial eye and upper lip.

Posterior of Body (Figure 13e): With small area with minute ridges bearing hairs.

Brush-like Organ (Figure 13e): Consisting of about 6 minute bristles near genitalia.

Y-Sclerite (Figure 13e): Typical for genus.

Eggs: USNM 158252 with small unextruded eggs.

COMPARISONS.—Philomedes hirutai resembles P. charcoti Daday, 1908:9, in having 2 bristles on the 2nd endopodial joint of the female 2nd antenna and 2 pegs on the tip of the 7th limb. It differs in having a rostrum with a concave distal margin, not convex as on P. charcoti. Also, the furcal claws of P. hirutai decrease fairly regularly in size, whereas, the anterior 5 claws are much stouter than the remaining claws on P. charcoti.

PSEUDOPHILOMEDINAE Kornicker, 1967

Five genera of Pseudophilomedinae have previously been reported from the study area: Tetragonodon Brady and Norman, 1896:667 (Kornicker, 1968:456), Paramekodon Brady and Norman, 1896:670 (Kornicker, 1968:464), Angulorostrum Kornicker, 1981:2 (Kornicker, 1981:10), Harbansus Kornicker, 1978:13 (Kornicker, 1981:16, 32, 39), and Pseudophilomedes Müller, 1893:358 (Kornicker, 1958:235). Only Pseudophilomedes and Harbansus are reported upon herein.

Pseudophilomedes Müller, 1893

TYPE-SPECIES.—Pseudophilomedes foveolatus Müller, 1894.

Only 1 species of Pseudophilomedes has previously been collected from the study area, Pseudophilomedes ferulanus Kornicker, 1958:235. The known range of that species is extended herein and 3 new species are described: P. ambon, P. polyancistrus, and P. zeta.

DISTRIBUTION.—Members of Pseudophilomedes have been reported from the Gulf of Naples (Müller, 1894:212), the Great Bahama Bank (Kornicker, 1958:235), Atlantic shelf of Georgia (Darby, 1965:26), North Carolina (Kornicker, 1967:8), Spanish Sahara and Mauritania (Kornicker and Caraion, 1977:4). The known depth range is 6–534 m (Kornicker and Caraion, 1977:47). The geographic range of the genus is extended herein to the continental shelf of the Gulf of Mexico off Florida, Louisiana, and Texas.