Rutiderma mollitum Darby 1965

Rutiderma mollitum Darby, 1965

Rutiderma mollita Darby, 1965:29, 58, pl. 15: figs. 1, 2 [female holotype: University of Michigan Museum of Paleontology; type-locality: “from 65 feet of water…offshore…vicinity of Sapelo Island, Georgia”].—Kornicker, 1975b:74.—Kornicker and Caraion, 1978:66 [compares to R. tridens].

Rutiderma mollitum.—Kornicker, 1983:2–7, 12, 13, 15, 25, 28–36, 54, 85, figs. 12–17.

DISTRIBUTION.—Northwest Atlantic: shelf off South Carolina to Florida; Gulf of Mexico: shelf off Florida, Alabama.

HABITAT.—Benthic; 5.4–190 m; salinity about 30‰ (Darby) and 35‰, 32°C, fine to coarse sand.

LIFE HISTORY AND ONTOGENY.—Female, male, 3–4 eggs.

Rutiderma mollitum Darby, 1965

Rutiderma mollita Darby, 1965:29, pl. 15: figs. 1, 2

HOLOTYPE.—UMMP 48791, female on 11 glass slides, Museum of Paleontology, The University of Michigan.

TYPE-LOCALITY.—Continental shelf off Sapelo Island, Georgia, depth 19.8 m.

MATERIAL.—Holotype; paratype, UMMP 48792 (2 slides, 1 with whole specimen with 1 valve removed, other with 4 eggs).

South Carolina continental shelf: USNM 158203, 1 juvenile female, sta 0177-2 (3E). USNM 158204, 1 adult female, sta 01774 (3E).

Georgia continental shelf: USNM 158207, 1 adult female, sta 0215-1 (5B). USNM 158205, 1 adult female, USNM 158001, 158004, 2 ovigerous females, sta 0215-3 (5B). USNM 158202, 1 juvenile male, sta 0230-3 (5E). USNM 158206, 1 juvenile female, sta 0243-2 (5H). USNM 158802, 1 specimen, sta 0220-5 (5C). USNM 158804, 2 specimens, sta 0220-6 (5C). USNM 158811, 2 specimens, sta 0531-4 (5F). USNM 158818, 4 specimens, sta 0531-6 (5F). USNM 158812, 1 specimen, sta 0540-5 (5H).

Florida continental shelf (Atlantic): USNM 158209, 1 adult male, sta 0265-3 (6E). USNM 158210, 1 juvenile male, sta 0269-2 (6F). 2 other specimens retured to D.K. Camp, collector.

Florida continental shelf (Gulf of Mexico), transect I: USNM 158708, 1 male, sta 2101. USNM 158781, 2 specimens, USNM 158723, 1 specimen, sta 2104. USNM 158729, 158731-158735, 8 specimens, sta 2105. Transect II: USNM 158772, 158774, 158783, 3 specimens, sta 2207. USNM 158700, 158701, 158661, 158655, 158659, 158736, 13 specimens, sta 2211. USNM 158715, 1 specimen, sta 2212. Transect IV: USNM 158760, 158761, 158766, 3 specimens, sta 2423. Transect V: USNM 158765, 158762, 2 specimens, sta 2531. Transect VII: USNM 158794, 1 specimen, sta 2747. USNM 158790, 158775, 158740, 3 specimens, sta 2748. USNM 158738, 1 male, sta 2749. Off Panama City: USNM 158832, 1 specimen.

Florida continental shelf (Southwest Florida): returned to James K. Culter, 16 specimens, sta 4; 40 specimens, sta 5; 2 specimens, sta 16; 6 specimens, sta 18; 1 specimen, sta 20; 1 specimen, sta 24; vial C; 1 specimen, vial E; 1 adult female, vial L.

Alabama continental shelf, transect VI: USNM 158746, 1 specimen, sta 2643.

DISTRIBUTION.—Continental shelf off South Carolina, Georgia, Florida (Atlantic and Gulf of Mexico), and Alabama. Known depth range 5.4190 m (Figure 3; Table 1).

SUPPLEMENTARY DESCRIPTION OF ADULT FEMALE (Figures 12–14).—Carapace oval in lateral view with minute incisur and no rostral overhang; posterior margin straight dorsal to small caudal process (Figure 12); posterodorsal margin truncate; anterodorsal and ventral margins convex; posterior lateral side of each valve with bulge having fairly well-defined posterior edge.

Ornamentation: 2 low, poorly to well-defined lateral ribs present, (1 dorsal and 1 ventral to central adductor muscle attachments) (Figure 12); vertical posterior rib joining posterior end of upper rib but may or may not connect with end of lower rib. Surface of each valve with numerous well-defined unusually small fossae; surface between fossae with abundant minute pits. Anterior outline of valve with small scallops. Bristles numerous along anteroventral, anterior, and ventral margins, and sparsely distributed on lateral surface.

Infold: Infold of rostrum with 8-12 bristles forming row parallel to anterior margin (Figure 13a); anteroventral infold with 10–13 bristles and about 8 ridges paralleling valve margin; posterior end of ventral infold continuing along infold of caudal process; posterior infold anterior to caudal process with 20–26 small bristles mostly close to and paralleling inner margin of infold (all bristles not shown on Figure 13b,c).

Caudal Process: Unusual in having concave ridge anterior to “pocket” of caudal process forming edge of valve and bearing lamellar prolongation of selvage (part of caudal process posterior to concave anterior ridge is outside selvage of valve); outer edge of concave ridge with single bristle near dorsal end (bristle lateral to selvage); posterior end of caudal process with 11–13 bristles forming row along inner edge (Figure 13b,c).

Selvage: Wide lamellar prolongation along anterodorsal, anterior, and ventral margins, narrower along posterior margin and anterior ridge of caudal processes (Figure 13a–c); lamellar prolongation faintly divided at inner end of small incisur; outer edge of lamellar prolongation with stout fringe along anterior and anteroventral valve margin; fringe becoming weaker and shorter posteriorly along the ventral valve margin, along the posterior valve margin dorsal to the caudal process, and along the anterodorsal valve margin; fringe absent on lamellar prolongation along anterior ridge of caudal process.

Central Adductor Muscle Attachment Scars (Figure 13h): Consisting of about 21 individual attachments.

Marginal Pore Canals: Branching, well developed.

Size: UMMP 48791, length 1.44 mm, height 1.02 mm; UMMP 48792, length 1.45 mm, height 1.05 mm (from Darby, 1965:29). USNM 158001, length 1.46 mm, height, 1.12 mm; USNM 158004, length 1.42, height 1.07 mm; USNM 158204, length 1.40 mm, height 1.03 mm; USNM 158207, length 1.46 mm, height 1.08 mm.

First Antenna (Figure 13i): 1st joint with few medial hairs and lateral spines. 2nd joint with spinous lateral bristle, spinous dorsal bristle, lateral spines forming row along distal margin, and few proximal spines forming rows along dorsal margin. 3rd and 4th joints fused; 3rd joint short with 3 spinous bristles (1 ventral, 2 dorsal); 4th joint long with 3 spinous bristles (2 ventral, 1 dorsal). Sensory bristle of long 5th joint with 3 or 4 short proximal filaments, 1 or no short filament near middle, faint short hairs along distal half, and spine at tip; long lateral hairs forming row at base of bristle. 6th joint minute, fused with 5th joint, with short spinous medial bristle. 7th joint: a-bristle spinous, reaching slightly past tip of bristle of 6th joint; b-bristle about 1½ times length of a-bristle, with 2 minute spines at tip; c-bristle about same length as sensory bristle of 5th joint, with 1 or no proximal filament, faint hairs along distal half and 2 minute spines at tip. 8th joint: d- and e-bristles bare with blunt tips, only slightly shorter than c-bristle; f-bristle stout, about two-thirds length of c-bristle, with 1 or no proximal filament, and with minute spine and hair at tip; g-bristle about same length as d-bristle, with 2 or 3 proximal filaments and spine at tip.

Second Antenna (Figure 13j): Protopodite bare. Endopodite 1-jointed with 4 proximal anterior bristles and a minute ventral spine on small node (node could be interpreted as small 2nd joint). Expodite: long 1st joint with small blunt medial bristle on distal margin; bristles of joints 2–5 fairly short, with ventral teeth, no natatory hairs; bristles of joints 6–8 with natatory hairs, no ventral teeth; 9th joint with 6 bristles (3 long and 1 medium with natatory hairs, 2 small bare); joints 6–8 with few faint, minute spines along distal lateral margins.

Mandible (Figures 14a,b): Coxale endite bifurcate, pectinate, and hirsute. Basale: dorsal margin with 3 distal bristles; medial side with 4 bristles in proximal ventral corner (2 short pectinate, unringed), and 3 bristles (2 short, 1 long) near middle of ventral margin. 1st endopodial joint with 2 ventral bristles, 1 minute spinelike bristle, and medial spines forming rows. 2nd endopodial joint: dorsal margin with 4 short proximal bristles; ventral margin with 2 short distal bristles followed by minute medial bristle on broad base, and then a stout terminal claw (stout claw with proximal dorsal peg, minute teeth along dorsal margin, and without upturned tip); medial side of joint spinous. 3rd endopodial joint with stout terminal claw with teeth along ventral margin, 1 unringed bristle (with ventral teeth) ventral to stout claw, 3 short medial bristles near ventral corner of base of stout claw, and 2 short bristles located lateral to base of stout claw of 2nd joint.

Maxilla (Figure 13d,l): Precoxale with dorsal hairs. Coxale with spinous dorsal bristle. Endite I with 5 bristles (3 stout pectinate, 2 ringed, spinous); endite II with 5 bristles (2 stout pectinate, 3 slender); endite III with 5 bristles (3 stout pectinate, 1 stout with stout marginal spines, 1 slender). Basale with 2 or 3 distal bristles (1 dorsal, 1 lateral, 1 ventral and medial). Exopodite small but well defined, with 3 bristles (2 long, 1 short) (Figure 13d). Endopodite: 1st joint with 1 spinous alpha-bristle and 1 spinous beta-bristle; 2nd joint with 2 stout, pectinate, unringed, clawlike bristles, and 5 (4?) ringed bristles with either marginal spines or teeth (dorsal of these tending to be clawlike).

Fifth Limb (Figure 13e,k): Endite I with 3 bristles (1 missing on illustrated limb); endite II with about 5 bristles; endite III with about 8 bristles (1 of these short, knifelike). Exopodite: 1st joint with 3 large teeth bearing secondary teeth followed by smooth tooth, and then a ringed bristle; a ringed bristle present on outer margin proximal to teeth; 2nd joint consisting of large flat tooth with 3 pointed lobes along inner margin; a ringed bristle present on inner margin proximal to teeth; posterior side with long proximal bristle, 2 bristles near proximal inner lobe, and a small bristle near distal outer corner; 3rd joint with 3 bristles on inner lobe and 2 on outer lobe; 4th and 5th joints fused, with total of 4 spinous bristles. (On 2nd exopodial joint of right limb of USNM 158004, the 3 bristles are on posterior side set back considerable distance from edge).

Sixth Limb (Figure 14c): Endite I with 3 bristles (proximal bristle with short spines, others with long hairs); endite II with 1 long spinous bristle and 1 short bristle with very long hairs; endite III with 4 bristles; endite IV with 3 bristles; end joint with 5 anterior bristles with long proximal hairs and short distal spines followed by 2 bristles with only long hairs; 2 short hirsute bristles in place of epipodial appendage.

Seventh Limb (Figure 14d): Each limb with 4 proximal bristles (2 on each side), and 6 terminal bristles (3 on each side); each bristle with up to 5 or 6 bells and marginal spines; terminus with opposing combs, one with about 11 teeth, other with about 7.

Furca (Figure 14e): Each lamella with 3 strong claws followed by 3 weak claws; all claws with teeth along posterior margin; teeth of strong claws consisting of long teeth between several smaller teeth; distal hairs present along anterior margins of strong claws; hairs present medially at bases of claws and following claws.

Bellonci Organ (Figures 13f 14f): Elongate, with broad middle part and pointed tip bearing few faint hairs.

Eyes: Medial eye tapering anteriorly, pigmented; dorsal margin of medial eye of USNM 158004 with short proximal process and pair of long distal bristle-like processes (Figure 14f); dorsal margin of medial eye of UMMP 48791 with total of 5 processes (Figure 13f). Lateral eyes small, unpigmented, each with 4 ommatidia (Figure 14f).

Posterior of Body (Figure 14e,g): Hirsute dorsal to furca; spines on surface of posterodorsal corner.

Upper Lip (Figure 14f): Simple, helmet-shaped.

Y-Sclerite (Figure 14e,g): Typical for family.

Genitalia (Figures 13g, 14e,g): Consisting of small oval on each side of body anterior to Y-sclerite.

Brushlike Organ (Figure 13g): Consisting of 7 minute bristles forming row near gentalia.

Eggs: UMMP 48791, 48972, each with 4 eggs (from Darby, 1965:29). USNM 158001 with 3 eggs. USNM 158004 with 4 eggs in marsupium.

DISCRIPTION OF ADULT MALE (Figures 15–17).—Carapace more elongate than that of female and with well-developed rostrum extending well past incisur (Figure 15).

Ornamentation (Figure 15): 2 poorly defined lateral ribs as on carapace of female. Anterior outline of rostrum with small scallops. Surface of each valve with numerous small round fossae and minute pits. Long bristles present along anterior and anteroventral margins and sparsely distributed over valve surface.

Infold: Infold of rostrum with 11 bristles forming irregular row parallel to valve edge; smaller bristles present along anteroventral infold; posterior end of ventral infold continuing along infold of caudal process, and posterior infold dorsal to caudal process with many small bristles mostly close to and paralleling inner margin of infold.

Caudal Process: Similar to that of female in medial view.

Size: UNSM 158209, length 1.47 mm, height 0.91 mm. USNM 158708, length 1.41 mm, height 0.86 mm. Returned to Mote Marine laboratory: sta 4E, length 1.43 mm, height 0.89 mm.

First Antenna (Figure 16a): 1st joint with distal medial spines forming rows. 2nd joint spinous, with 2 bristles (1 dorsal, 1 lateral). 3rd joint short, with dorsal hairs and lateral spines, and 3 bristles (2 dorsal, 1 ventral). 4th joint about twice length of 3rd, spinous, with 4 bristles (1 dorsal, 3 ventral). 5th joint minute, inserted ventrally between 4th and 6th joints; sensory bristle with numerous filaments at distal end of broad proximal part; stem of sensory bristle with minute proximal filament and spine at tip (stem becoming narrower just past end of 8th joint). 6th joint slightly longer than 4th, with 1 medial bristle near dorsal margin. 7th joint: a-bristle about same length as bristle of 6th joint; b-bristle stout, slightly longer than twice length of a-bristle, with 2 proximal filaments, 1 spine distal to middle, and 1 spine at tip; c-bristle extremely long, with 11 filaments with 2 spines at tip. 8th joint: d- and e-bristles longer than b-bristle, bare with blunt tips; f- bristle similar to c-bristle, also with 11 filaments with 2 minute spines at tip; g-bristle stout, longer than d- and e-bristles, with 2 proximal filaments and minute spine at tip.

Second Antenna: Protopodite bare. Endopodite 3-jointed (Figure 16b): 1st joint short, with 5 bristles (4 proximal, 1 near middle); 2nd joint elongate with 2 spinous ventral bristles; 3rd joint elongate, reflexed on 2nd, with 1 short proximal bristle and 2 small bristles at tip (tip with ridges). Exopodite: elongate 1st joint with spines forming rows along ventral margin and small blunt medial bristle on distal margin; bristle of short 2nd joint about same length as combined lengths of 3rd and 4th joints, with ventral closely spaced spines (proximal spines stouter than distal spines); bristle of long 3rd joint long with natatory hairs, no spines; bristles of short joints 4–8 similar to bristle of 3rd joint; 9th joint with 5 bristles (3 long, 1 medium, all with natatory hairs, and 1 minute with few short marginal spines); joints 3–8 each with small basal spine; 9th joint with small lateral spine about one-half length of joint (spine about same length as basal spine of 8th joint); 2nd joint with long hairs forming 2 rows along distal lateral margin; joints 3–8 with spines along part of distal lateral margin.

Mandible (Figure 16c): Coxale endite represented by 2 or 3 minute weakly developed processes. Basale: medial side spinous with 6 bristles on or near ventral margin (1 of these without rings); dorsal margin with 3 bristles either proximal to middle (right limb, USNM 158209) or near it (left limb, USNM 158209). Exopodite well developed, hirsute distally. 1st endopodial joint with medial spines and 2 ventral bristles. 2nd endopodial joint: medial side spinous; dorsal margin with 1 short and 3 long proximal bristles; ventral margin (or close to it) with 6 short distal bristles. End joint with 1 stout claw and 4 slender bristles.

Maxilla (Figure 16d): Limb reduced. Endites I to III with faint bristles, hirsute. Precoxale and coxale dorsal fringe of hairs; coxale with stout hirsute dorsal bristle. Basale with 1 spinous medial bristle near dorsal margin and 1 spinous ventral bristle. Exopodite with 3 spinous bristles. Endopodite: 1st joint hirsute ventrally, with 1 bare alpha-bristle and 1 beta-bristle with long proximal hairs; end joint with 7 bristles.

Fifth Limb (Figure 17a): Endite I with 4 bristles; endite II with 5 bristles; endite III with about 7 bristles. Exopodite: joints 1 and 2 each with about 5 bristles, some unringed, flattened, and with few minute spines; joint 3 with 2 stout hirsute bristles on outer lobe, and about 2 slender bristles on inner lobe; remaining joints fused, with total of 4 bristles. Epipodial appendage with about 38 bristles.

Sixth Limb (Figure 17b): 2 short hirsute bristles in place of epipodial appendage. Endite I with 3 short bristles; endite II with 2 bristles (1 long, 1 short); endite III with 4 bristles (2 long, 2 short); endite IV with 3 bristles (2 long, 1 short). End joint with 1 slender anterior bristle with short marginal spines followed by 3 slender bristles with long proximal hairs and short distal spines and then 3 stouter hirsute bristles.

Seventh Limb (Figure 17c): 4 short proximal bristles, 2 on each side, and 4 longer terminal bristles, 2 on each side; proximal bristles with 2 or 3 bells and marginal spines; terminal bristles with 4 or 5 bells and marginal spines. Terminus with opposing combs having 2 teeth on 1 comb and 3 on other.

Furca (Figure 17d): Similar to that of female except for main claws and especially the 1st claw being more elongate, and teeth along claw 1 being of similar size.

Bellonci Organ (Figure 17e: Edges crinkled in part proximal to weak suture near broad middle part; distal part tapering to pointed tip.

Eyes: Lateral eye pigmented black, with about 30 ommatidia (exact number difficult to determine because of black pigment) (Figure 17e, only ommatidia along unpigmented edge shown). Medial eye with brown pigment, only slightly smaller than lateral eye; USNM 158209 with 5 elongate processes along dorsal margin (Figure 17e).

Posterior of Body: With short spines along middle part.