Stemonopa, EFFORD AND HAIG, 1968

BOYKO, CHRISTOPHER B., 2002, A Worldwide Revision Of The Recent And Fossil Sand Crabs Of The Albuneidae Stimpson And Blepharipodidae, New Family (Crustacea: Decapoda: Anomura: Hippoidea), Bulletin of the American Museum of Natural History 2002 (272), pp. 1-396 : 222-228

STEMONOPA EFFORD AND HAIG, 1968 Stemonopa Efford and Haig, 1968: 908 . – Haig,

1974: 449 (list).– Coêlho and Calado, 1987: 41.

– Calado, 1995: 271. Stemenopa [sic] Efford, 1969: 5. Stemenops [sic] Kaestner, 1980: 336. Stomonopa [sic] Calado, 1987: 96.

DIAGNOSIS: Carapace as long as wide, front broad, anterior margin armed; hepatic anterolateral spine absent; branchiostegite armed. Rostrum absent. Distal peduncular segments cylindrical, longer than body, with large corneas. Antennular segment I unarmed; dorsal flagellum with 43–45 articles, ventral flagellum with four articles. Antennal segment I unarmed; flagellum with seven articles. Maxilliped III carpal projection long; weak crista dentata; exopod slender. Pereopod I dactylus with dorsal margin smooth; propodal cutting edge smooth; distodorsal carpal spine present. Males with large coxal pore on pereopod III. Telson of male elongate triangular, fully calcified. Telsons exhibiting weak sexual dimorphism.

DISTRIBUTION: Known only from Western Australia.

TYPE SPECIES: Stemonopa insignis Efford and Haig, 1968 , by monotypy.

REMARKS: Given the limited number of times this genus has been cited in the literature, it is remarkable that three incorrect spellings have been given. Only the type species is known.

Stemonopa is the sister taxon to Albunea , and it differs primarily in the shape and length of the distal peduncular segments and characters of the antennae and antennules, as well as several carapace features such as the lack of a rostrum. This genus is intermediate between Italialbunea and Albunea sensu stricto.

Stemonopa insignis Efford and Haig, 1968 Figures 73 , 74

Stemonopa insignis Efford and Haig, 1968: 908– 912 , figs. 8–10. – Haig, 1974: 447 (list). – Coêlho and Calado, 1987: table 1. – Calado, 1995: 272–275, pl. 87, figs. a–i. – Boyko and Harvey, 1999: 400 (list), 402 (key).

MATERIAL EXAMINED: Australia: Western Australia: Sta. 03B02BT, northwest shelf, 19°56.8̍S, 117°53.5̍E, 44 m, June 25, 1983, coll. CSIRO: 1 Ƌ, 9.7 mm cl ( QM W22309) ; Sta. 01B06BT, northwest shelf, 19°04.4̍S, 118°47.5̍E, 83 m, Feb. 16, 1983, coll. CSI­ RO: 1 anterior half (unsexable), 7.6 mm cl ( QM W22310) ; Sta. Bone­NW Shelf–379, off Kimberley, 18°46.97̍S, 120°14.48̍E, 76

m, July 1, 1999, coll. Y. Bone: 1 Ƌ, 10.1 mm cl ( MOV J47318 ).

DIAGNOSIS: As for genus.

DESCRIPTION: Carapace (fig. 73A) length and width subequal. Anterior margin slightly concave on either side of ocular sinus, becoming convex laterally with 9–12 large spines (n = 2) along length. Rostrum absent. Ocular sinus smoothly concave and unarmed. Frontal region smooth; setal field narrow anteriorly and broad posteriorly; posterior lateral elements united with lateral, oblique, hepatic elements. CG1 parallel to anterior margin of carapace, sinuous, strongly crenulate, medial and posterior lateral elements united. Mesogastric region smooth; CG2 present as three short medial elements; CG3 broken into six short elements between posterior lateral elements of CG1; CG4 with one short, anteriorly displaced, medial element between longer supralateral elements of CG4. Hepatic region smooth, with oblique posteriorly directed setose groove at median of lateral margin, intersecting posterior elements of CG1; curved anteromedially directed setose groove intersecting anterolateral margin of medial CG1 element. Epibranchial region generally triangular, smooth; posterolateral margin without rows of setae. Metagastric region smooth; CG5 absent. CG6 strongly crenulate, strongly anteriorly concave medially and sloping out to anteriorly convex lateral thirds. CG7 oblique, not reaching lateral margins of median segment of CG6. Cardiac region smooth; CG8 present as one long medial element. CG9 present as two short lateral grooves with gap at midline. CG10 present as two long oblique elements. CG11 absent. Post­CG11 element absent. Branchial region with numerous short, transverse rows of setae in posterior half. Posterior margin deeply and evenly convex, with submarginal groove reaching posterior margin of posterior concavity. Branchiostegite with strong anterior submarginal spine; anterior region with scattered short transverse lines ventral to linea anomurica; with many short rows of setae and sparsely covered with long plumose setae ventrally; posterior region membranous, with numerous irregular fragments and sparsely covered with long plumose setae.

Ocular plate (fig. 73C) subdivided into anterior and posterior elements; anterior ele­ ment oblong with shallow median indentation; posterior element triangular and tapering posteriorly; proximal ocular segments not visible, likely fused with ocular plate. Distal peduncular segments (fig. 73B) hyper­elongate, proximally flattened and distally cylindrical, 1.5 times length of carapace, with convex proximolateral and straight proximomesial margins, cornea covering distal tip; mesial margins approximated along length; proximomesial margins with short plumose setae.

Antennule (fig. 73D) with segment III width subequal proximally and distally; with plumose setae on dorsal and ventral margins and sparsely scattered on lateral surface; dorsal exopodal flagellum with 43–45 articles (n = 2), long plumose setae on dorsal and ven­ tral margins; ventral endopodal flagellum short with four articles (n = 2) and plumose setae on dorsal and ventral margins. Segment II medially inflated in dorsal view, with plumose setae on dorsal and ventral margins. Segment I wider than long, unarmed; dorsal half of lateral surface rugose, with long plumose setae; long plumose setae on dorsal and ventral margins.

Antenna (fig. 73E) with segment V approximately two times longer than wide, with long plumose setae on dorsal and ventral margins; flagellum with seven articles (n = 2), long plumose setae on dorsal, ventral, and distal margins. Segment IV expanded distally, with long plumose setae on dorsal and ventral margins. Segment III with long plumose setae on dorsal and ventral margins. Segment II short, widening distally, rugose, with plumose setae on margins and scattered on lateral surface; antennal acicle long, thin, and reaching distal margin of segment IV, with long plumose setae on dorsal margin. Segment I rounded proximally, flattened ventrolaterally, with long plumose setae on margins and scattered on surface; lateral surface unarmed, without lobe; segment with ventromesial antennal gland pore.

Mandible, maxillule, and maxilla unknown.

Maxilliped I (fig. 73F) endite tapered distally and subequal to first segment of exopod. Exopod with two segments; proximal segment narrow, margins parallel; distal segment spatulate, longer than wide, broadest medially. Endopod flattened and elongate, reaching to distal end of proximal exopodal segment.

Maxilliped II (fig. 73G) dactylus evenly rounded, length slightly greater than width. Propodus 1.5 times wider than long, slightly produced at dorsodistal angle. Carpus not produced dorsodistally, approximately two times longer than wide. Merus approximately 2.5 times longer than wide, margins parallel. Basis­ischium incompletely fused. Exopod one­half longer than merus, flagellum with one elongate article, longer than carpus.

Maxilliped III (fig. 73H) dactylus with rounded tip; long plumose setae on margins and lateral surface. Propodus dorsolaterally inflated, with longitudinal median row of plumose setae on lateral surface; margins with plumose setae. Carpus produced onto propodus almost three­fourths length of propodus; lateral surface with two rows of plumose setae on surface; plumose setae on margins. Merus inflated, unarmed, with plumose setae on margins and scattered on lateral surface. Basis­ischium incompletely fused, with crista dentata of six teeth. Exopod two­segmented; proximal segment small; distal segment styliform, tapering, approximately three­fourths length of merus; with plumose setae on margins; without flagellum.

Pereopod I (fig. 74A) dactylus curved and tapering; lateral and mesial surfaces smooth; dorsal margin with long plumose and short simple setae; ventral margin with short simple setae. Propodal lateral surface with numerous short, transverse rows of setose rugae; dorsal margin unarmed; ventral margin distally produced into acute spine; cutting edge lacking teeth, lined with long plumose setae; dorsal margin with long plumose setae, ventral margin with short simple setae. Carpus with dorsodistal angle produced into strong corneous­tipped spine; dorsal margin with short transverse grooves behind spine; dorsal and distal margins with long plumose setae; lateral surface with small distal rugose area, with transverse setose ridges on distal half of surface; mesial surface smooth, margins with long plumose setae. Merus unarmed; lateral surface with scattered transverse rows of short plumose setae, margins with long plumose setae; mesial surface with few scattered setae; fully calcified. Basis­ischium incompletely fused, unarmed. Coxa unarmed.

Pereopod II (fig. 74B) dactylus smooth; base to heel straight, heel low and rounded, heel to tip with broad indent, tip subacute, tip to base broadly convex; lateral surface smooth, with several small tufts of short setae in generally straight line across medioproximal surface, several widely spaced submarginal tufts of short setae dorsodistally; mesial surface smooth, ventral margin with long plumose setae, dorsal margin with short simple setae, with patch of long plumose setae at base. Propodal dorsal surface smooth, with ventral margin inflated and rounded; oblique row of long plumose setae on distal margin of lateral surface; distal and ventral margins with long plumose setae; dorsolateral surface as narrow, oblique, flattened shelf, with long setae on dorsal and ventral margins; mesial surface with elevated, curved setose ridge from ventral junction with dactylus almost to ventral proximal junction with carpus. Carpus strongly produced and rounded dorsodistally, dorsal mar­ gin smooth; lateral surface smooth, with irregular, interrupted row of rugae and submarginal elevated ridge ventrally, rugae and ridge with long plumose setae; margins with long plumose setae; mesial surface smooth with row of long plumose setae distally and subdorsally. Merus with thin median decalcified window, with long plumose setae on distodorsal and ventral margins; mesial surface nearly smooth, with few scattered setae. Basis­ischium incompletely fused and unarmed. Male coxae unarmed; female coxae unknown.

Pereopod III (fig. 74C) dactylus with base to heel convex, heel low and rounded, heel to tip with broadly concave indent, tip subacute, tip to base smoothly convex; lateral surface smooth, dorsodistal margin with tufts of short setae; ventral margin with long plumose setae, dorsal margin with short simple and plumose setae; mesial surface smooth, with plumose setae proximally at junction with propodus. Propodus not inflated dorsoventrally; lateral surface smooth, with long plumose setae in oblique row; dorsolateral surface narrow, oblique, flattened, with long plumose setae on dorsal and ventral margins; mesial surface smooth. Carpus produced dorsodistally approximately to median of propodus; dorsolateral margin unarmed; lateral surface slightly rugose in dorsodistal half, with mat of short setae and two broken rows of setae ventrally; mesial surface smooth. Merus smooth, with small oval decalcified window medially; dorsal and ventral margins unarmed, with long plumose setae on distodorsal and ventral margins; mesial surface smooth. Basis­ischium incompletely fused and unarmed. Male coxae unarmed; female coxae unknown. Female presumably with large gonopore on anterior mesial margin of coxa; male with large pore.

Pereopod IV (fig. 74D) dactylus with base to tip gently convex, tip rounded, tip to base straight distally to convex proximally; lateral surface smooth (setal pattern of dactylus and mesial surface unknown). Propodus expand­ ed dorsally and ventrally; ventral expansion reaching ventral margin of dactylus, margin with long plumose setae; dorsal expansion with row of long plumose setae dorsally, oblique area with mat of short simple setae; lateral and mesial surfaces smooth. Carpus produced dorsodistally; ventral two­thirds of lateral surface and mesial surface smooth, dorsodistal third of lateral surface with mat of short setae; dorsal margin with short simple and long plumose setae; ventral margin with short simple setae; mesial surface smooth. Merus lateral surface with scattered short, transverse rows of short setae, dorsal margin with long plumose setae; proximoventral quarter of mesial surface decalcified. Basis­ischium incompletely fused and unarmed. Coxa unarmed.

Abdomen (fig. 74E) with somite I longer than wide, widest posteriorly; dorsal surface with anterior margin concave; posterior margin curved, with elevated submarginal row of short setae and few scattered short setae anterior to elevated row; small transverse decalcified windows laterad of segment medi­ an. Somite II dorsal surface with submarginal transverse ridge anteriorly; with small transverse decalcified windows laterad of segment median just anterior to submarginal ridge; pleura expanded and directed anterolaterally; lateral margins angled, anterior and lateral margins with long plumose setae, posterior margin with short setae; posteromesial angle with long mat of short simple setae extending more than one­half length of pleura. Somite III similar to somite II, but narrower, shorter; pleura thinner and shorter than on somite II, directed posterolaterally proximally and curving anterolaterally distally, with setae as in somite II except with thin row of short setae near posterior margin; anterolateral angle subacute; dorsal surface obliquely flattened anterolaterally, with row of short setae on posterior margin of flattened region. Somite IV similar to somite III, but thinner and shorter; dorsal surface with few short setae posterolaterally; pleura thinner and shorter than on somite III, directed laterally; dorsal surface obliquely flattened anterolaterally; margins with long plumose setae. Somite V wider than somite IV; lateral margins with plumose setae; pleura absent. Somite VI slightly broader than somite V; dorsal surface with short transverse rows of setae laterad of midline and on posterior margin; pleura absent.

Females presumably with uniramous, paired pleopods on somites II–V; males without pleopods.

Telson of male (fig. 74F) broadly triangular, longer than wide, proximal half with straight margins, distal half with concave margins, tip broadly rounded; thickly calcified medially, inflated dorsally; slightly decalcified laterally; median longitudinal groove extending one­half length, row of long simple setae of either side of median groove beginning at median and continuing almost to distal margin of telson; proximolateral angles with patch of short simple setae; margins with long simple setae. Telson of female (fig. 74G) flattened, ovate, lateral and distal margins convex, tip rounded (setal pattern unknown).

DISTRIBUTION: Known only from Western Australia, in 44–83 m depth.

MAXIMUM SIZE: Males: 10.1 mm cl; females: 10.4 mm cl.

TYPE SPECIMEN: WAM 61–62 (♀ holotype, lost).

TYPE LOCALITY: 5 mi offshore, north of Maud’s Landing, Point Maud, Western Australia, 31 fms (= 56.7 m).

REMARKS: A study of living specimens would allow a better understanding of the functional usage of the extraordinarily long distal pedunclar segments in this species. In particular, it is difficult to envision how the animal is able to move through the sediment without causing damage to the peduncles.

The holotype was lost in the mail en route to Brazil (Hewitt, personal commun.). The three specimens cited above are the only oth­ er specimens known at this time. Calado (1995), due to the loss of the holotype, saw no material of this species and redescribed it based on the text and illustrations of Efford and Haig (1968).

Figures

Fig. 73. Stemonopa insignis Efford and Haig, 1968: A–E, H, unsexable specimen, 7.6 mm cl, QM W22310; F, G, ♀, 10.4 mm cl, WAM 62–62, holotype (from Efford and Haig, 1968). A. Carapace, branchiostegite, and ocular peduncles, dorsal view. B. Ocular peduncles, proximal, dorsal view. C. Ocular peduncles, distal, dorsal view. D. Left antennule, lateral view. E. Left antenna, lateral view. F. Left maxilliped I, lateral view (from Efford and Haig, 1968). G. Right maxilliped II, lateral view (from Efford and Haig, 1968). H. Left maxilliped III, lateral view. Scale = 1.1 mm (B, C), 1.6 mm (D), 2.2 mm (E, G, H), 2.6 mm (F), and 3.3 mm (A).

Fig. 74. Stemonopa insignis Efford and Haig, 1968: A, unsexable specimen, 7.6 mm cl, QM W22310; B, C, D (part), E, F, Ƌ, 9.7 mm cl, QM W22309; D (part), G, ♀, 10.4 mm cl, WAM 61–62, holotype (from Efford and Haig, 1968). A. Left pereopod I, lateral view. B. Right pereopod II, lateral view. C. Right pereopod III, lateral view. D. Right pereopod IV, lateral view (part of dactyl from Efford and Haig, 1968). E. Abdominal somites I–VI, dorsal view. F. Telson of Ƌ, dorsal view. G. Telson of ♀, dorsal view (from Efford and Haig, 1968). Scale = 1.7 mm (F), 1.9 mm (G), 2.2 (A), and 3.3 mm (B–E).