Rutiderma ferax Kornicker ex Kornicker & Thomassin 1998

Rutiderma ferax

ETYMOLOGY.—From the Latin ferax (fertile).

HOLOTYPE.—Adult female on slide and in alcohol.

TYPE LOCALITY.—BT-836, residual pool.

PARATYPES.—None

DISTRIBUTION.—Collected only at type locality.

DESCRIPTION OF ADULT FEMALE (Figures 58–60).—Carapace rugose with 2 stout horizontal ribs (1 dorsal and 1 ventral to central adductor muscle attachments) (Figure 58); ventral part of carapace with 7 broad radial riblets extending to ventral edge; anterodorsal part of carapace anterior to valve midlength with 6 radial riblets extending to anterodorsal edge; adjacent to 6th radial riblet a shallow sulcus extends from dorsal valve margin to dorsal horizontal rib.

Ornamentation: Surface with abundant small fossae; bristles numerous along ventral and anterior margins and sparse on lateral surface; anterior and ventral edges of valve scalloped (Figure 59a).

Infold: Anterodorsal infold above minute angle (angle indicates location of incisure) with 8 bristles forming row paralleling anterodorsal margin (Figure 59a); anteroventral infold striate, with 8 bristles forming row paralleling anteroventral margin. Infold of caudal processes with pocket having 5 or 6 small bristles along dorsal edge (Figure 59b,c); 3 or 4 additional bristles anterior to pocket seemingly a continuation of bristles forming row along dorsal edge of pocket; 3–5 minute pores, some with slender hair-like bristles, present near inner edge of ventral infold in vicinity of pocket. Posterior infold of left valve with small bristle dorsal to caudal process (Figure 59c).

Selvage: Lamellar prolongation with marginal hairs along anterior of valve just dorsal to incisur, along both anteroventral margin and anterior part of ventral margin, and possibly along posterior margin, bare elsewhere including anterodorsal margin. Prolongation undivided at tip of caudal process, but whether divided at incisur unclear.

Central Adductor Muscle Attachments (Figure 59d): About 14 ovoid attachments at valve midheight just anterior to midlength.

Carapace Size (length, height in mm): Holotype, 1.16, 0.87.

First Antenna (Figure 59e,f,h): 1st joint with distal row of few medial spines, and 2 rows of minute proximal lateral spines near dorsal margin (lateral spines not shown). 2nd joint with row of proximal dorsal spines, row of distal lateral spines near dorsal margin, 1 spinous dorsal bristle, and 1 shorter lateral bristle. 3rd joint fused to 4th, with 3 spinous bristles (1 ventral, 2 dorsal). 4th joint elongate with 1 dorsal bristle and 2 ventral bristles (1 very long almost reaching tip of sensory bristle of 5th joint, 1 shorter reaching past 8th joint). 5th joint with row of lateral spines (not shown) near base of sensory bristle; sensory bristle with 3 small proximal filaments, 2 minute spines at midlength, 1 minute subterminal spine, and 1 minute terminal spine. 6th joint minute, fused to 5th, with spinous medial bristle. 7th joint: a-bristle slightly longer than bristle of 6th joint, with few indistinct spines; b-bristle about same length as a-bristle, with 2 minute spines (1 at midlength and 1 terminal); c-bristle about same length as bristle of 5th joint, with small proximal filament, minute distal spine, and minute terminal spine. 8th joint: d- and e-bristles slightly shorter than c-bristle, bare with blunt tips; d-bristle very slightly longer and stouter than e-bristle; f-bristle with 2 small proximal filaments, 1 minute distal spine, and 1 minute terminal spine; distal of bristle crooked, slender, with narrowly spaced rings; g-bristle with 2 fairly long proximal filaments and minute terminal spine, distal of bristle crooked, slender, and with narrowly spaced rings. Lateral side of fused 7th and 8th joints with 2 minute processes (1 proximal to base of d-bristle, other proximal to space between c- and e-bristles (not shown)). (Correction: Konricker (1992:142) described the 1st and 2nd joints of the 1 st antenna of the female Rutiderma rex as having lateral spines near the ventral margin; it should have been dorsal margin in both instances.)

Second Antenna: Protopodite bare (Figure 59g). Endopodite comprising single joint with 4 medial anterior bristles of similar length and 1 indistinct, minute, posterior, ventral, unringed spine with base slightly lateral (Figure 59g). Exopodite: long 1st joint with small terminal tubular bristle just ventral to joint midheight; bristles of joints 2–5 about same length (equal to combined length of joints 1–9), with minute blunt spines along ventral margin and recurved tips; bristles of joints 6–8 long (equal to twice combined lengths of joints 1–9), with natatory hairs, no spines; 9th joint with 6 bristles (3 long and 1 medium with natatory hairs, 2 minute, lateral, bare); all joints without spines.

Mandible (Figure 60a–c): Coxale endite bifurcate, both branches with long hairs near base and pectinate. Basale: dorsal margin with 3 bristles at midlength; ventral margin with 7 bristles (2 proximal, unringed, pectinate, others ringed either bare or with marginal spines). Exopodite absent. 1st endopodial joint triangular, with rows of medial spines and 2 small ringed ventral bristles. 2nd endopodial joint: medial surface with rows of spines; dorsal margin with 3 or 4 bristles; ventral margin with 1 terminal a-bristle, 1 terminal b-bristle in form of small processes with terminal, ringed, tubular bristle; 1 stout claw-like unringed c-bristle with proximal dorsal tooth and serrate dorsal margin; and 2 lateral d-bristles. 3rd endopodial joint: 3 ringed a-bristles; b-bristle unringed, claw-like, with ventral teeth perpendicular to bristle; c-bristle stout claw-like unringed, with small teeth along ventral margin except near tip, and slight bulge at distal dorsal corner (Figure 60c).

Maxilla: 3 well-developed endites, each with 2 or 3 stout terminal pectinate claw-like bristles and additional ringed bristles. Coxale with short dorsal bristle. Basale with 2 short bristles (1 ventral, 1 dorsal). 1st endopodial joint with 1 spinous alpha-bristle and 1 spinous beta-bristle. 2nd endopodial joint with rows of medial spines near dorsal margin, 2 stout pectinate claw-like bristles, and several ringed bristles. Exopodite small with 3 bristles.

Fifth Limb: With 3 endites. 1st exopodial joint with 4 teeth: proximal tooth somewhat obscured but appearing bifurcate distally; 2nd to 4th teeth with marginal cusps; 1 bristle proximal to proximal tooth and 1 proximal to distal tooth (Figure 60d,e). 2nd exopodial joint comprising large flat tooth having 3 lobes on inner margin (proximal lobe with pointed marginal cusp, middle lobe with 2 marginal cusps (1 rounded, 1 pointed), distal lobe smooth without cusps); posterior side of tooth with 1 long proximal bristle, a pair of shorter distal bristles, and small ringed bristle near outer edge (Figure 60d,f). 3rd exopodial joint with 3 bristles on inner lobe and 2 on outer lobe (Figure 60g). Fused 4th and 5th exopodial joints with total of 4 spinous bristles (Figure 60g).

Sixth Limb (Figure 60h): With 2 epipodial bristles. Endite I with 3 bristles; endite II with 2 bristles; endite III with 3 bristles; endite IV with 2 bristles. End joint with 6 bristles (anterior 3 with short marginal spines, next with long proximal and short distal spines, posterior 2 plumose; posterior bristle set back from edge); joint with row of lateral hairs near anterior edge. All bristles ringed (rings not shown).

Seventh Limb (Figure 60i): 4 bristles in proximal group, 2 on each side, each bristle with 2 or 3 bells and distal marginal spines. 6 bristles in terminal group, 3 on each side, each with 2–5 bells and distal marginal spines. Terminus with opposing combs with indistinct teeth (about 3 on 1 side, 4 on other).

Furca (Figure 60j): Each lamella with 3 stout claws followed by 3 smaller claws; long hairs along margin of lamellae following claws; claws 1–3 with distal slightly crooked; tips of claws 1 and 2 slightly rounded, tip of claw 3 either pointed or slightly rounded; tips of claws 4–6 slender and pointed; claws with slender closely spaced spines along posterior margins (not shown); claw 1 with distal hairs along anterior margin; claws 1 and 2 with row of medial hairs near base; anterior edge of right lamella proximal to claw 1 with few hairs; right lamella anterior to left by width of base of claw 1.

Bellonci Organ (Figure 59h,i): Elongate with wrinkles or sutures at midlength delimiting segment with striate surface (visible with ×15 ocular and ×100 objective; not shown); tip narrowly rounded with terminal spine and few indistinct hairs (Figure 59h).

Eyes: Medial eye unpigmented; dorsal margin of eye of holotype with round proximal bulge, then single filament and a bifurcate filament (Figure 59h,i). Lateral eye smaller than medial eye, unpigmented, with 4 ommatidia (Figure 59h).

Upper Lip (Figure 59h): Simple, rounded in lateral view.

Posterior of Body (Figure 60j,k): Hirsute in ventral half and with few long hairs or spines on dorsal corner anterior to dorsal end of girdle.

Genitalia (Figure 60k): A small brownish indistinct oval on each side of body anterior to furca.

Y-Sclerite (Figure 60j,k): Without ventral branch.

COMPARISONS.—Rutiderma ferax is very similar to R. rex. The main difference noted is in the infold of the caudal process of the carapace: the ridge dorsal to the pocket is straight or slightly convex and forms a 45° angle in R. rex (see Kornicker, 1992, fig. 82b,c) and is a shallow concave arc more-or-less parallel to the ventral edge of the caudal process in R. ferax (Figure 59b,c). The length of the carapace of the female R. ferax is 1.16 mm, compared to 0.90–0.92 mm (three specimens) for R. rex (Kornicker, 1992:142). The caudal process has greater posterior projection in R. ferax. The anterodorsal and anteroventral infolds of R. rex each bears four or five bristles compared to eight on R. ferax. The endopodite of the 2nd antenna of R. ferax bears a small posterior spine absent on R. rex. The proximal and middle lobes of the 2nd exopodial joint of the 5th limb of R. ferax bear one or two marginal cusps absent on R. rex. The Y-Sclerite of R. rex bears a ventral branch absent on R. ferax.