Montucaris distincta, Jaume & Boxshall & Bamber, 2006

Jaume, Damià, Boxshall, Geoff A. & Bamber, Roger N., 2006, A new genus from the continental slope off Brazil and the discovery of the first males in the Hirsutiidae (Crustacea: Peracarida: Bochusacea), Zoological Journal of the Linnean Society 148 (2), pp. 169-208 : 172-202

publication ID	https://doi.org/ 10.1111/j.1096-3642.2006.00235.x
DOI	https://doi.org/10.5281/zenodo.10544843
persistent identifier	https://treatment.plazi.org/id/95245720-2711-FB6A-FF13-3D533A75F952
treatment provided by	Felipe
scientific name	Montucaris distincta
status	sp. nov.

Treatment

MONTUCARIS DISTINCTA View in CoL SP. NOV. ( FIGS 1–29 View Figure 1 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7 View Figure 8 View Figure 9 View Figure 10 View Figure 11 View Figure 12 View Figure 13 View Figure 14 View Figure 15 View Figure 16 View Figure 17 View Figure 18 View Figure 19 View Figure 20 View Figure 21 View Figure 22 View Figure 23 View Figure 24 View Figure 25 View Figure 26 View Figure 27 View Figure 28 View Figure 29 )

Material examined

South Atlantic Ocean off Brazil, between 22°38′S / 40°27′W and 22°40′S / 40°24′W; fine silt bottoms, 619– 778 m depth; February–March 2001 GoogleMaps .

Holotype: Brooding female (oostegites fully developed, setose), body length ( BL) 5.30 mm ( MSUSP Reg. no. 17045).

Female paratypes: Fifty-four brooding specimens, of which 18 measured: BL 4.63, 5.95, 5.70 and 5.23 mm [ MSUSP Reg. no. 17046] and 5.51, 5.45, 4.60, 5.26, 4.80, 5.04, 4.60, 4.75, 5.43, 5.17, 5.03, 5.10, 5.08 and 5.43 mm ( BMNH Reg. nos. 2005.401–410]. Two preparatory specimens (with oostegite buds), of which one measured, BL 3.81 mm ( BMNH Reg. nos. 2005.411– 412]. Seven preparatory specimens (oostegites with setation not fully developed), of which two measured: BL 4.45 and 4.49 mm ( BMNH Reg. nos. 2005.413– 419]. Two brooding specimens prepared for SEM and one dissected for study of musculature.

Male morph-I paratypes (see description below): Seven specimens, of which one measured, BL 3.70 mm with P1 and P3–P4 missing, P2 and uropods both with distal part of endopod missing ( MSUSP Reg. no. 17047). One specimen with PL1 – PL5 dissected, rest of body in vial; body size not determined owing to damage to specimen. One specimen used for SEM observations .

Male morph-II paratypes (see description below): One specimen BL 3.88 mm with well-preserved P7, pleopods, uropods and telson; P1–P4 with distal portion of endopod missing; P5–P6 missing except coxa and proximal part of basis. One specimen partially dissected with pleopods 3–5 loose in vial, PL1–2 accidentally lost; P1, P5, PL1–5 and uropods well preserved; P2–P4 and P6 with distal portion missing; P7 missing; body size not determined due to damage to specimen, not measured, well preserved, dissected for study of musculature ( BMNH reg. nos. 2005.430–432) .

Juvenile male paratypes (pleopods not fully developed): Specimen BL 3.64 mm, with P1–P3 with distal parts missing, P4 and P6 missing, and exopods of uropods missing. One damaged specimen (body anterior to 5th pereonite – bearing P4 – missing), not measured; retaining P5, pleopods and uropods except exopod ( BMNH Reg. nos. 2005.420–427) .

Manca paratypes: One damaged manca stage-III (pereopod 7 not fully developed, and exopods on rest of pereopods more developed than in adult, and inserted laterally on basis), with anterior part of body (in front of 4th pereonite, bearing P3) missing; one manca stage-IV (exopods of pereopods as in adult in development and insertion; pereopod 7 not fully developed), 3.10 mm ( BMNH Reg. nos. 2005.428–429) .

Description

Brooding female ( Figs 1A View Figure 1 , 2–7 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7 , 9–17 View Figure 9 View Figure 10 View Figure 11 View Figure 12 View Figure 13 View Figure 14 View Figure 15 View Figure 16 View Figure 17 )

Body vermiform, subcylindrical ( Fig. 1A View Figure 1 ), with surface ornamented with numerous fine setules and comb rows ( Figs 2A View Figure 2 , 4 View Figure 4 , 5B View Figure 5 , 6A View Figure 6 ). Proportional lengths of cephalothorax: pereon: pleon (including telson) 0.11: 0.43: 0.46, respectively. Cephalothorax incorporating maxilliped-bearing first thoracomere only; broad in dorsal view ( Fig. 2A View Figure 2 ), slightly wider than long, excluding rostrum; dorsal cephalothoracic shield produced frontally into small anteroventrally curving rostrum, acutely pointed at tip. Paired lateral folds of dorsal shield ellipsoid in outline, longer than wide, defined basally by complete suture line ( Figs 3 View Figure 3 , 7A View Figure 7 ). Dorsal shield without transverse groove and lacking posterodorsal extension (= carapace fold).

Pereonites becoming successively larger posteriorly; pereonite 1 much shorter than rest ( Figs 1A View Figure 1 , 2A View Figure 2 , 4A View Figure 4 ); vestigial pleurae present anterolaterally on pereonites 4–7 ( Fig. 4A View Figure 4 ). Pleonites 1–5 free, becoming successively longer towards posterior, slightly depressed dorsoventrally, with vestigial pleurae on pleonites 1–4 ( Figs 1A View Figure 1 , 4B View Figure 4 , 5B View Figure 5 , 6A View Figure 6 ). Sixth pleonite similar to preceding somites and apparently distinct from telson in dorsal view, but mid-dorsal suture line between sixth pleonite and telson non-functional, lacking arthrodial membrane; pleotelson present: ventral suture line marking plane of articulation between sixth pleonite and telson absent; no interruption in ventral longitudinal trunk muscles.

Rear part of pleotelson representing telson ( Figs 5B View Figure 5 , 6C View Figure 6 ) longer than wide, tapering gradually towards posterior; cylindrical in section; anus opening ventroterminally, closed off by paired anal valves projecting beyond rear margin; valves ornamented with fine hair-like setules. Armature comprising five stout spinulate spines along lateral margins, long slender seta arising dorsolaterally and short, smooth spine located dorsally on posterior margin ( Fig. 5B View Figure 5 ). Entire surface of telson ornamented with short crescentic spinule rows.

Antennule ( Fig. 2A, C View Figure 2 ) with short, unequal flagella; surfaces of peduncular segments and both flagella densely ornamented with crescent-shaped scales with setular fringes or with crescentic rows of setules. Peduncular segments provided with intrinsic muscles inserting on proximal rim of primary and accessory flagellar branches. Segment 1 longest. Some setae on segments 1 and 2 penicillate. Segment 3 shortest, produced dorsally into terminal setiferous process armed with three setae and several short, apparently tubular elements ( Fig. 2D View Figure 2 ). Accessory flagellum located dorsomedially on distal margin of third peduncular segment, indistinctly five-articulate. Primary flagellum shorter than accessory flagellum, located ventrolaterally on distal margin of third peduncular segment, bearing two subapical aesthetascs and four unequal, apical setae.

Antenna ( Figs 2A, B View Figure 2 , 5A View Figure 5 ) with protopodal segments characterized by presence of intrinsic musculature ( Fig. 8B View Figure 8 ): segment 1 (coxa) with short intrinsic muscle inserting on proximal rim of segment 2 (basis), long second muscle originating in coxa passing through basis and inserting on proximal rim of first endopodal segment; long intrinsic muscle originating in basis and inserting on rim of first endopodal segment, short intrinsic muscle originating midway along basis inserting on proximal rim of exopodal scale. First to third endopodal segments each with pair of opposing intrinsic muscles inserting on rim of adjacent distal segment. Fourth endopodal segment annulated, forming flagellum; six component articles not defined by intrinsic musculature. Coxa short, unarmed; basis almost three times longer than maximum width, with oblique distal surface bearing rami, unarmed. Antennal scale cylindrical, with array of ten setae along inner and distal margins. First endopodal segment short, articulating with second segment at oblique joint; segments 3 and 4 elongate.

Labrum large, trapezoidal in posterior aspect, with distal margin produced into evenly rounded lappet folded backwards ( Figs 3 View Figure 3 , 9A View Figure 9 ). Anterior surface with rows of thick spinules; surface with transverse constriction about midway ( Fig. 3 View Figure 3 ). Posterior surface globose, but becoming deeply concave subdistally. Ornamented with short setules on margins and dense array of setules on posterior surface ( Fig. 7E View Figure 7 ).

Labium ( Figs 3 View Figure 3 , 14A, B View Figure 14 ) formed by paired paragnaths; each paragnath lobate, tapering abruptly to elongate, terminal process ornamented with scattered hair-like setules with expanded tip basally, process naked distally; inner surface irregular, forming small bilobed process at inner distal angle densely ornamented with fine hair-like setules; bilobed process with striated sclerotized plate along inner margin ( Fig. 14B View Figure 14 : c); row of three spines present on distal margin adjacent to process, innermost spine simple, curved with blunt tip, middle and outer spines with angled tips and with denticles along oblique inner distal margin. Surface of paragnath lobe ornamented with numerous rows of slender spinules, becoming stouter closer to margin. Posterior surface of lobe with two small processes (labelled a and b in Figs 3 View Figure 3 , 14A View Figure 14 ).

Mandibles ( Fig. 9B–F View Figure 9 ) comprising coxa with welldeveloped gnathobase and three-segmented palp. Coxal gnathobase with flattened and concave distal portion (see cutaway section in Fig. 3 View Figure 3 ), with widely separated incisor and molar processes; ventral surface of gnathobase irregular in outline with numerous small spinous projections; with scattered spinule rows ventrally and fine hair-like setules dorsally near bases of elements composing setal row between incisor and molar. Right mandible ( Fig. 9D View Figure 9 ) incisor orientated at about right angle to remaining edge of mandible, with three larger and three smaller cusps ( Fig. 9E View Figure 9 ), separated by concave gap from rounded expansion on dorsal margin of gnathobase, armed with row of about 31 spines; distalmost spine short, bifid and blade-like, next three spines also bifid and blade-like, but more slender and with pectinate tips ( Fig. 9F View Figure 9 ); remaining spines simple, becoming progressively more slender, longer and setiform; 5–6 spines at proximal end of row becoming progressively shorter. Molar process columnar, directed medio-ventrally (see Fig. 3 View Figure 3 : m. p.), with grinding surface sclerotized and smooth; series of faintly striated, imbricating scales distributed along proximal margin of grinding surface, descreasing in size towards proximo-dorsal angle. Left mandible with four-cusped incisor inserted at about right angle to remaining edge of mandible ( Fig. 9C View Figure 9 ); lacinia mobilis five-cusped, with appearance similar to incisor and orientated parallel to it; three spines placed adjacent to lacinia, most proximal bifid and hirsute, remaining two spines simple, hirsute, blade-like. Dorsal margin of gnathobase with swelling bearing spine row, separated by distinct gap from distal cluster of three spines terminating in lacinia mobilis; this proximal row comprising 18 setiform spines, more distal spine with strongly defined basal swelling, swelling less well defined in innermost spines. Mandibular palp threesegmented; first segment short, unarmed; middle segment unarmed; distal segment slightly bowed, with three apical setae; palp inserted on clearly defined dorsolateral pedestal on gnathobase (see Figs 3 View Figure 3 , 9D View Figure 9 ); relative lengths of segments: 0.13: 0.40: 0.47.

Maxillule ( Fig. 10E View Figure 10 ) lacking palp, comprising two segments, coxa and basis, each produced into welldeveloped endite; surfaces of both segments ornamented with crescentic rows of setules. Coxa with distinct, unarmed lobe distally on postero-lateral surface, near articulation with basis (cf. Fig. 10E View Figure 10 : c and Fig. 3 View Figure 3 : c); coxal endite (= inner lobe) with distal armature of five setae: dorsal two setae bipinnate in distal half, middle seta smooth with multicuspid tip, next seta ornamented with single row of denticles on one side and pinnate on other, ventral seta pappose. Surface of endite ornamented with stout spinules dorsally, and with fine hair-like setules around ventral convex margin. Basal endite (= outer lobe) slightly bilobed at tip, each lobe armed with distinctive setal elements; plus two isolated pappose setae located subdistally on posterior surface ( Fig. 10F View Figure 10 ). Posterolateral lobe bearing complete linear array of 17 setae, becoming progressively shorter from outer to inner end of row, structure and ornamentation of expanded bifid tips of setae also changing gradually along row as in Figures 10E View Figure 10 and 7C View Figure 7 . Anteromedial lobe armed with 12 setae arranged in double row ( Fig. 10G View Figure 10 ); setae typically stout, blade-like, armed with row of short spinules, one seta longer and with bifid tip.

Maxilla ( Fig. 11A, B View Figure 11 ) two-segmented; proximal segment representing coxa with inner margin produced distally into indistinctly bipartite endite; distal segment produced into two distally directed lobes, and bearing small, non-articulated process with long, apical pappose seta, tentatively interpreted here as representing vestigial endopod (cf. Fig. 11A, B View Figure 11 : e and Fig. 3 View Figure 3 : e). Structure located proximal to limb interpreted as pedestal with posterolateral conical process carrying opening of maxillary gland (cf. Fig. 11A View Figure 11 : m.g., Fig. 3 View Figure 3 : m.g. and Fig. 7D View Figure 7 ), and with anterolateral process ( Fig. 11A View Figure 11 : d) positioned opposing posterolateral lobe on coxa of maxillule (see Fig. 3 View Figure 3 : c and d). Coxal medial margin elongate, with double row of marginal setae; 12 setae composing posterior row slightly shorter than setae of anterior row, pappose proximally with strong pinnules all around but becoming bipinnate distally; tips of setae stout and denticulate, as in Fig. 11G View Figure 11 ; 13 View Figure 13 setae composing anterior row slender, ornamented unilaterally with short spinules distally. Coxal endite indistinctly bipartite, divided into proximal and distal parts defined by change in setation. Distal part displaying row of ten marginal setae becoming progressively shorter from distal to proximal end of row; proximal two of these setae pappose with tuft of hair-like setules proximally and unilaterally denticulate distally ( Fig. 11D View Figure 11 ), rest unilaterally ornamented with distal brush of hair-like setules and proximal row of denticles; proximal three of these brush-like setae with subapical sensilla, giving tip bifid appearance ( Fig. 11F View Figure 11 ); two additional setae implanted subdistally close to each other on posterior surface of distal part of coxal endite ( Fig. 11C View Figure 11 ), proximal seta pappose with unilateral tuft of setules proximally, distal seta with series of transverse lamellar structures proximally. Proximal part of coxal endite with six unequal setae ( Fig. 11B, D View Figure 11 ) heterogeneously ornamented, as follows from proximal to distal end of row: one uniformly bipinnate, next thick and pappose, next slender and smooth with tricuspidate tip, next with distal brush and subapical sensilla ( Fig. 11E View Figure 11 ), next stout and smooth, and finally next similar to preceding seta but with bicuspid tip (see Fig. 11B View Figure 11 ). Two pappose setae with smooth distal portion positioned proximally on integumental fold on posterior surface of coxal endite ( Fig. 11A View Figure 11 : s), plus tiny thorn-like seta proximally on anterior surface ( Fig. 11A View Figure 11 : t). Posterior surface of coxa with stout isolated spinulate seta situated adjacent to coxa–basis joint ( Fig. 11A View Figure 11 : u); spinules along one side of seta longer than counterparts on other side. Entire posteromedial surface of coxa densely ornamented with tufts of short spinules, tufts located closer to anteromedial margin with spinules somewhat longer and finer; tufts area delimited laterally by single row of spatulate spinular elements ( Figs 7F View Figure 7 , 11A, B View Figure 11 ).

Proximal endite of maxillary basis ( Figs 10C, D View Figure 10 , 11B View Figure 11 ) about three times longer than wide, with oblique distal margin armed with three parallel rows of setae; most proximal row, located subdistally on posterior surface, consisting of six setae, each unilaterally pectinate distally and with row of denticles proximally on other side; apical surface of lobe occupied by distal row of six and adjacent subdistal row of 12 similar, unilaterally pectinate in distal part, rake-like blunt setae. Surface of endite ornamented with irregular, short rows of spinules, as in Figure 10C View Figure 10 ; wide pore visible proximally on posterior surface of endite. Distal endite ( Figs 7B View Figure 7 , 10A, B View Figure 10 , 11B View Figure 11 ) with oblique distal margin armed with row of 13 rake-like, blunt setae plus additional row of four similar setae near outer apical angle of lobe. Lobe with short rows of spinules irregularly scattered over surface as figured.

Maxilliped ( Fig. 12 View Figure 12 ) uniramous, comprising short coxa, elongate basis produced into distal enditic lobe and five-segmented endopod; exopod absent. Coxa short, ornamented with fine hair-like setules laterally and with irregular spinule rows medially. Basis elongate, with complex setal armature and ornamentation. Lateral margin of basis with two short setae close to coxa–basis articulation, longer seta also positioned proximally and long pappose seta with bluntly rounded tip located just proximal to origin of endopod. Medial margin of basis mostly unarmed except for short, blunt proximal seta. Linear array of 18 setae with increasingly modified and elaborate ornamentation towards distal end of row placed postero-medially on segment; more distal setae ornamented with lamellar hyaline elements; seta 17 with slightly expanded distal section bearing serrate flange; all setae except 18 with tiny sensilla subdistally. Surface of basis with tufts of long spinules located marginally near setal row, and longer setules providing dense covering anteriorly.

Maxillipedal basal endite with isolated plumose seta proximally and three rows of setae along oblique distal margin; anteriormost row comprising nine pappose setae with bluntly rounded tips (cf. Fig. 12A View Figure 12 : f and Fig. 3 View Figure 3 : f); middle row with most proximal element pappose on along one side only, then six long, robust setae, each ornamented with two rows of denticles in middle to distal region and single row of setules in distal third (cf. Fig. 12A View Figure 12 : g and Fig. 3 View Figure 3 : g), distalmost five of these six setae each with apical pore; posterior row comprising three bipinnate setae (cf. Fig. 12A View Figure 12 : h and Fig. 3 View Figure 3 : h). Short, modified seta with bluntly, rounded tip with tiny spinules placed midway of lateral margin of endite (cf. Fig. 12A View Figure 12 : i and Fig. 3 View Figure 3 : i). Surface of endite with scattered spinules and spinule rows, and with patches of integumental scales proximally.

Maxillipedal endopod ( Figs 3 View Figure 3 , 12B View Figure 12 ) implanted posterolaterally to basal endite, five-segmented; all segments ornamented with spinule rows. Segmental setation formula: 2, 3, 10–11, 4–5, 5–6; either three or four apical setae modified as claw-like elements; setae ornamented as figured.

Pereopods of typical peracarid type (cf. Hessler, 1982), i.e. all displaying monocondylic articulation between coxa–basis, and dicondylic articulation between rest of podomeres; hinge line of articulations perpendicular to limb plane except that between merus–carpus, which is parallel to it. Junction between body and coxa ovoid, with long axis orientated more or less parallel to main body axis ( Fig. 4A View Figure 4 ); hinge points of articulation between coxa and body not observed, but: (i) (limited) abduction/adduction possible at this plane (demonstrated by manipulation with probe) suggesting hinge line runs about parallel to main axis of junction between coxa and body in pereopods 2–7; whereas (ii) limited promotion-remotion at this level in pereopod 1 suggests hinge line running about perpendicular to main axis of body. Invaginated condyle of coxa–basis articulation projecting inward posterolaterally from distal end of coxa in pereopods 6–7 (see Fig. 18C View Figure 18 ), and turning progressively more lateral from pereopod 5 to 1. Coxa–basis joint defined by insertion of one intrinsic and six extrinsic muscles ( Fig. 13A View Figure 13 ) around proximal rim of basis; one anteriorly located extrinsic muscle inserting at coxa–body joint.

Pereopods (P1 to P7) biramous except P7, each with short annular coxa well delimited and clearly separate from corresponding sternite; P1 extended forward under mouthparts. Basis of P1 conspicuously bowed at insertion of exopod; rest of bases of pereopods roughly straight. Exopods inserted anterolaterally on proximal part of basis, those of P1 and P2 indistinctly twosegmented, setal formula 1 + 1, 2; exopods of P3 and P4 indistinctly three-segmented, setal formula 1 + 1, 1 + 1, 2; exopods of P5 and P6 vestigial, reduced to single segment with three terminal setae. Oostegites present on P2 to P6, inserted on posteromedial surface of coxa, becoming successively larger from P3 to P6; that of P2 somewhat reduced; oostegites falcate, with numerous long setae along margins; setae pappose proximally, plumose along rest of shaft. Endopods of P1, P2, P6 and P7 each five-segmented, segments corresponding to ischium, merus, carpus, propodus and dactylus, bearing unguis (but note that articulation between basis and ischium of endopod of P6 is not completely expressed; see Fig. 15C View Figure 15 ; and that articulation between ischium and merus of P2 is not completely expressed in some specimens). Free endopod of P3, P4 and P5 four-segmented due to complete (although vestiges of articulation expressed in P5; see Fig. 17C View Figure 17 ) failure of separation of ischium from basis as indicated also by musculature signature (see Fig. 13B View Figure 13 ), with intrinsic muscles actuating ischium– merus joint originating just distal to level of nonexpressed basis–ischium joint.

Dactylus of P1 ( Fig. 14C, D View Figure 14 ) with two inner spines with rounded, expanded tip; unguis spatulate. P2 endopod heavily built, with unguis apparently absent ( Fig. 15A View Figure 15 ); three stout barbed spines on distomedial angle of carpus; two parallel rows, each comprising six barbed spines, along distomedial margin of propodus; two shorter barbed spines terminally on dactylus; one short denticulate spine positioned distolaterally on propodus ( Fig. 15B View Figure 15 ). P3 ( Figs 13A, B View Figure 13 , 16A View Figure 16 ) with four stout triangular spines on anterior margin of compound basis–ischium, isolated spine on anterodistal margin of merus, and row of up to 12 spines along anterior margin of carpus; one slender barbed spine subdistally on posterior margin of carpus, plus two similar slender barbed spines subdistally on posterior margin of propodus. P4 ( Fig. 17A View Figure 17 ) with one hyaline triangular spine distally on anterior margin of carpus, and six barbed spines on posterior margin of segment ( Fig. 17B View Figure 17 ); propodus with two slender barbed spines on posterior margin ( Fig. 17B View Figure 17 ). P5 ( Fig. 17C View Figure 17 ) with five and one slender barbed spines on posterior margin of carpus and propodus, respectively. Propodus of P6 with six slender barbed spines on posterior margin ( Fig. 15C View Figure 15 ). Endopod of P7 slender, lacking marginal spines; dactylus with stout penicillate seta subterminally on lateral margin, as in P6 ( Fig. 15D, E View Figure 15 and Fig. 15C View Figure 15 , respectively). Unguis of P3–P7 elongate, acicular. Propodus of latter limbs with transverse row of long setae (extending beyond tip of corresponding unguis) distally on anterior margin of segment.

Pleopods reduced. PL 1 to PL 3 each represented by pair of setae inserted directly onto ventral surface of body ( Figs 4B View Figure 4 , 6A View Figure 6 ); outer seta naked, inner seta penicillate. PL 4–5 ( Figs 4B View Figure 4 , 6A, B View Figure 6 ) each represented by isolated outer seta arising directly from body surface and inner tapering non-articulated process bearing short inner seta and two unequal penicillate setae distally.

Uropod ( Figs 5B View Figure 5 , 6C View Figure 6 ) protopod with powerful extrinsic muscles inserting around proximal rim ( Fig. 13C View Figure 13 ); intrinsic muscles mostly inserting on proximal rim of rami; one oblique intrinsic muscle inserting near base of large spine at inner distal angle. Endopod ‘segments’ lacking any intrinsic musculature, corresponding to superficial annulations in internal structure.

Protopod armed with 3–4 stout spines along inner margin, proximal spine shortest, distal spine longest, proximal and middle spines with subdistal sensilla on tip; spines denticulate with few, sparsely set strong denticles placed proximally; proximal swelling on dorsal surface of segment with three setae. Exopodal segment 1 bearing one inner and five outer setae, four proximal setae on outer margin reduced; segment 2 with three long outer setae, two long distal setae, and two unequal setae subdistally on outer margin. Endopodal annuli 1–5 with, respectively, two, one, one, one and one inner spines with subdistal sensilla on tip similar to those on protopod; additional setation comprising nine, three, three, two and setae, respectively, several penicillate; setal ornamentation as figured; first article with row of about 12 strong triangular spinules along inner margin. Surface of limb ornamented with short crescentic spinule rows.

Male morph-I ( Figs 1B View Figure 1 , 18–21 View Figure 18 View Figure 19 View Figure 20 View Figure 21 , 22A View Figure 22 )

Similar to female (with well-developed mouthparts) except for display of penes and absence of oostegites, smaller body size ( Fig. 1B View Figure 1 , 3.70 View Figure 3 mm vs. 4.60–5.95 mm in brooding females), morphology of rostrum, antennules and pleopods, and some aspects of armature of P3, uropods and telson. Rostrum short, directed downwards ( Fig. 18B View Figure 18 ). Telson ( Fig. 18D View Figure 18 ) displaying only four marginal spinulate spines (five in female), and with dorso-distal stout spinulate spine instead of tiny smooth spine present in homologous position in female (cf. Figs 5B View Figure 5 , 18D View Figure 18 ).

Antennule ( Figs 18A, B View Figure 18 , 19A View Figure 19 ) with armature not fully resolved owing to specimen damage. Peduncular segment 3 produced dorsally into setiferous process with at least three penicillate setae (armature of process probably not fully resolved). Primary flagellum inserted ventrolaterally on distal margin of third peduncular segment, comprising seven flagellar articles; articles wider than long except distal two; armature of articles missing except isolated aesthetasc on distomedial angle of articles 5–6, and five unequal setae on tip of distal article; nevertheless flagellum packed full of conspicuous nerves, dividing off from dense central nerve bundle at base of antennule and with longitudinal fibres inserting at distomedial angle of each article, possibly innervating clusters of aesthetascs lost during sampling and/or sorting (see condition in proximal article of main flagellum in male morph-II; Fig. 23B, C View Figure 23 ). Accessory flagellum originating dorsomedially on distal margin of third peduncular segment, comprising six articles; articles becoming successively shorter towards tip, proximal article elongate, with distal margin reaching that of article 4 of main flagellum.

Third pereopod with triangular spines on anterior margin of basis–ischium differing from female by transformation of most proximal spine into two more slender elements (cf. Figs 16A View Figure 16 and 22A View Figure 22 ). Penes tubular, smooth, located on sternite of eighth thoracomere close to seventh pereopods ( Figs 1B View Figure 1 , 18C View Figure 18 ).

Pleopods well developed on all pleonites, natatory ( Fig. 1B View Figure 1 ). Protopods with distinct lateral cuticular outgrowth proximally, subcylindrical, somewhat depressed antero-posteriorly, becoming successively shorter from first to fifth pleopod; short smooth lateral seta at one-third of distance along margin, plus seta submarginally at two-thirds of distance along medial margin; patch of stout spinules between insertion of latter seta and distomedial angle of segment. PL 1 ( Fig. 20A View Figure 20 ) and PL 3 ( Fig. 21A View Figure 21 ) similar, with partially annulated, apparently multisegmented rami, although muscle signature suggests one-segmented condition; hardly developed digitiform lobe crowned with one penicillate seta on postero-lateral margin of endopods; arrangement of setae on rami as figured. PL 4 ( Fig. 21B View Figure 21 ) and PL 5 ( Fig. 21C View Figure 21 ) with rami similar to PL 1 and PL 3 except digitiform lobe of endopod now powerfully developed and crowned with two penicillate setae instead of one. PL 2 ( Fig. 20B, C View Figure 20 ) with both rami modified: exopod apparently two-segmented and shorter than endopod, proximal segment naked, distal segment elongate with three distal setae, innermost long and plumose, other two short and smooth; additional short seta subdistally on lateral margin of segment; endopod one-segmented, with four plumose setae distally; proximal portion of segment slightly expanded, with hardly developed digitiform process crowned with penicillate seta on posterolateral surface; anterior surface of segment with rounded outgrowth at about two-thirds of distance of segment; tiny rounded process placed on same surface just above outgrowth (see Fig. 20C View Figure 20 ).

Uropod ( Fig. 19B View Figure 19 ) differing from female as follows: (i) annulations on endopod not expressed dorsally and intersegmental articulation on exopod incompletely expressed medially (articulation fully expressed in female); (ii) middle of five setae on outer margin of exopodal segment 1 short and spiniform (vs. all setae normal in female; cf. Figs 6C View Figure 6 and 19B View Figure 19 ); (iii) second exopodal segment with three marginal setae on each side and two distal setae (only two setae, located subdistally, on outer margin of segment in female). Endopod differing from female in: (iv) presence of additional long spine terminally on distal article; (v) ornamentation of all spines, uniformly serrate and lacking subapical sensilla (except short subdistal spine), with serrations formed by hyaline lamellae (all spines sparsely denticulate proximally and with subapical sensilla in female); (vi) greater number of penicillate setae on dorsal surface of proximal article; (vii) length of spines on articles longer than in female (cf. Figs 6C View Figure 6 and 19B View Figure 19 ); and (viii) condition of outer bipinnate setae on endopodal articles 1–4, shorter and stouter than in female, with stronger pinnules reaching stout tips of setae (distal portion of setae smooth in female; cf. Figs 6C View Figure 6 and 16B View Figure 16 ).

In addition, male morph-I does not express basis–ischium articulation on P5 (expressed laterally only in female), whereas on P6 this articulation is fully expressed (again expressed laterally only in female).

Male morph-II ( Figs 8 View Figure 8 , 23–29 View Figure 23 View Figure 24 View Figure 25 View Figure 26 View Figure 27 View Figure 28 View Figure 29 )

Body aspect ( Fig. 23A View Figure 23 ) similar in most major features to male morph-I, but with strikingly different integumental ornamentation of pereonites and pleonites, in particular in honeycombed pattern of hyaline frill extensions (see Fig. 24C View Figure 24 ; and Fig. 23A View Figure 23 ). Body size (3.88 mm) slightly greater than male morph-I (3.70 mm). Cephalothoracic structure differing, with transverse suture line present on dorsal cephalothoracic shield just behind plane of articulation of mandibles; line clearly visible in all three specimens available ( Figs 23B View Figure 23 , 24A View Figure 24 ). Telson ( Fig. 24B View Figure 24 ) with spines longer than in male morph-I (cf. Figs 18D View Figure 18 , 24B View Figure 24 ); spines differing in ornamentation also, being serrate with hyaline lamellae rather than spinulate; two small scars on dorsal surface could correspond to insertion of (missing?) setae; integument displaying honeycombed pattern of hyaline frills ( Fig. 24C View Figure 24 ).

Antennule ( Figs 8A View Figure 8 , 23B, C View Figure 23 ) sharing basic structure with male morph-I; robust peduncular segments defined by presence of intrinsic muscles ( Fig. 8A View Figure 8 ); one pair of intrinsic muscles originating in segment 1 and inserting proximally in segment 2; long unpaired muscle originating in segment 1 passing without intermediate attachment to insert in segment 3; intrinsic muscle pair originating in segment 2 inserting in segment 3; pair arising in segment 3 inserting at base of accessory flagellum. Putative differences in ornamentation not evaluated as many elements missing in available specimens of both morphs; peduncular segment 3 with dorsal setiferous process armed with at least eight short spiniform setae plus three penicillate setae (only socles of latter preserved in specimen illustrated in Fig. 23B, C View Figure 23 ); segment displaying oblique suture line subdistally on dorsal surface, just behind setiferous process. Primary flagellum comprising at least six articles (antennules broken off beyond this article); articles wider than long except distalmost; armature of articles not preserved except cluster of four aesthetascs on dorsodistal angle of proximal article. Accessory flagellum comprising six articles; proximal article elongate, with distal margin extending beyond article 5 of main flagellum (article shorter in male morph-I, its distal margin reaching only distal margin of article 4 of main flagellum; cf. Figs 19A View Figure 19 , 23B View Figure 23 ); two simple setae per article arranged as in Figure 23A, B View Figure 23 .

Antenna ( Fig. 23D View Figure 23 ) longer than antennule (cf. Fig. 23A View Figure 23 ), similar to male morph-I; armature of segments unresolved (missing in all specimens), as well as number of articles comprising flagellum (distal portion missing from all specimens).

Mouthparts regressed, almost devoid of armature elements but still displaying diagnostic filiform extension of paragnaths, three-segmented mandibular palp, outlet of maxillary gland, and maxillipedal palp ( Figs 23A View Figure 23 , 24A View Figure 24 ).

Pereopod 1 ( Fig. 25A View Figure 25 ) similar to male morph-I. P2– P4 and P6 with distal part of endopod missing. P2 ( Fig. 26A View Figure 26 ) with three strong barbed spines on carpus, as in morph-I. P3 differing from morph-I in number, size and arrangement of triangular spines on anterior margin of basis–ischium, with up to ten unequal spines, vs. only four present in morph-I (cf. Figs 22A View Figure 22 , 26B View Figure 26 ); in addition, merus and carpus (missing in morph-I) differing also from condition displayed in female in number of triangular spines on anterior margin (five and 17 spines on merus and carpus of male morph-II, vs. one and 13 in female; cf. Figs 16A View Figure 16 , 26B View Figure 26 ). P4 ( Fig. 26C View Figure 26 ) differing from morph-I ( Fig. 17A View Figure 17 ) in retaining lateral vestige of intersegmental articulation between basis and ischium (vs. complete failure to separate segments), and by the structure of proximal seta on posterior (= medial) margin of basis, which is comparatively shorter, with an expanded tip. P5 and P6 ( Fig. 25B, C View Figure 25 ) similar to morph-I but with three proximal setae on basis comparatively shorter and with expanded tips; apart from this, P5 and P6 differing also in retaining lateral vestige of intersegmental articulation between basis and ischium (segments completely merged in P5, and fully articulated in P6 of morph-I). P7 ( Fig. 25D View Figure 25 ) similar to morph-I except for two proximal setae on basis, with expanded tips, and by absence of long penicillate seta on outer margin of propodus. Exopods on P2 to P6 similar in segmentation, armature and relative dimensions to those of morph-I.

Pleopods differing from morph-I in squamose integument of protopod, with tightly set crescentic hyaline frills, and longer and less stiff distal setae on both rami. Pleopodal musculature as in morph-I: extrinsic muscles ( Fig. 29B View Figure 29 ) short, originating on lateral body wall and inserting proximally in protopodal part; protopods with pair of powerful intrinsic muscles anteriorly and three shorter muscles (two exopodal and one endopodal); long muscle extending from base to near tip of both exopod and endopod and short oblique muscle present within proximal endopodal segment ( Fig. 29A–D View Figure 29 ). PL 1 ( Figs 27A View Figure 27 , 29A View Figure 29 ) and PL 3 ( Fig. 28A View Figure 28 ) lacking postero-lateral digitiform process present proximally on margin of endopod in morph-I. PL 4 ( Figs 28B View Figure 28 , 29D View Figure 29 ) and PL 5 ( Fig. 28C View Figure 28 ) as in morph-I in major features. PL 2 ( Figs 27B, C View Figure 27 , 29B, C View Figure 29 ) with exopod as in morph-I; but endopod much more inflated, with three long plumose setae distally and another seta subdistally on inner margin (four distal setae at this position in morph-I); proximo-lateral margin of segment evenly rounded, lacking digitiform process (present in morph-I), with short seta; anterior and posteromedial surface of segment hardly sclerotized, inflated, bilobed anteriorly, evenly rounded posteromedially; anterior surface lacking tiny rounded process present at this location in morph-I.

Uropod ( Fig. 24D View Figure 24 ) biramous, with basic structure similar to morph-I ( Fig. 19B View Figure 19 ); but differing in: (i) condition of three spines on inner margin of protopod, long and serrate, with hyaline serrations and lacking subapical sensilla; (ii) outer margin of segment with naked seta at outer distal angle (two setae in morph- I); (iii) exopodal segment 1 with five outer setae (six setae in morph-I); (iv) endopodal proximal article lacking row of spinules along inner margin (row present in morph-I); (v) setae on outer distal angle of endopodal articles 2–4 plumose and slender (stout and pinnate in morph-I). Extrinsic musculature ( Fig. 13C View Figure 13 ) originating within sixth pleonite and inserting around proximal rim of undivided protopods; intrinsic musculature ( Fig. 13C View Figure 13 ) well developed, with large muscles originating proximally within protopod and inserting on the proximal rims of both rami; additional short muscles lying obliquely in distal part of segment, inserting near base of inner angle spine. Exopod with single intrinsic muscle. Endopod lacking intrinsic muscles ( Fig. 13C View Figure 13 ). Surface of limb ornamented with honeycombed pattern of hyaline frill extensions (as in Fig. 24C View Figure 24 ).

Juvenile male

Not figured. Body 3.64 mm long. As male morph-I in most major features, but with pleopods not fully developed. Pleopods with well-developed protopod but with both rami represented by buds; no armature developed on rami except setae on posterolateral digitiform process of endopod, fully developed already at this stage; pleopod 2 as rest of pleopods, not modified as in adult. Additional differences from male morph-I in armature of endopod of uropod, as follows: (i) distal annulus lacking long terminal spine; (ii) spines on all annuli ornamented as in female, i.e. sparsely denticulate proximally and with subapical sensilla (spines uniformly serrate and lacking sensilla, with serrations formed by hyaline lamellae in male morph-I); and (iii) outer bipinnate setae on articles 1–4 as in female, i.e. longer and more slender than in male morph-I, with distal portion smooth; condition of exopod unknown as ramus missing in both available specimens. Penes hardly developed, less than half length of those of adult.

Manca stages ( Fig. 22B View Figure 22 )

Two specimens identified as manca stages sensu lato as P7 not fully developed, representing different stages, referred to as stage III and stage IV. Single damaged specimen with portion of body anterior to third pereonite missing considered manca stage-III ( Fig. 22B View Figure 22 ). Pereopods of this specimen recognized as P3 to P7 based on display of buds of diagnostic triangular spines of P3 on anterior margin of basis–ischium of anteriormost pereopod (although segments were damaged and are not figured). Pereopods differing from adult in lateral – but not anterolateral – insertion of exopod on proximal part of basis. Exopods on P5 powerfully developed compared with adult; P6 displaying indistinctly two-segmented exopodal bud. Pleon with pleopods not developed, but paired rudiments present in form of two, two, three, three and three setae located posteriorly (midway, on pleonite 5) on each side of ventral surface of pleonites 1–5, respectively. Fifth pleonite distinctly more elongate than rest. Pleonite 6 with biramous uropods attached ventrolaterally midway along segment; posterior margin of segment apparently rounded, probably damaged, with terminal anal opening. Telson indistinct, apparently fully incorporated into last pleonite. Uropods biramous with elongate protopod, two-articulated endopod and one-segmented exopod (probably distorted proximally in Fig. 22B View Figure 22 ); armature as figured; note ornamentation of stout spines on inner margin of endopod, resembling male morph-I rather than morph-II.

Manca stage-IV (not figured) 3.10 mm long, as brooding female in all respects except in incomplete development of P7 and absence of oostegites.

Remarks

The new genus differs from Hirsutia and Thetispelecaris , the two other hirsutiid genera, currently known only from females, in the presence of a series of stout triangular spines along the anterior (= lateral) margin of the basis–ischium, merus and carpus of P3. These processes are absent in the other two genera. In addition, Montucaris carries a proximal row of about 12 strong triangular spinules along the medial margin of the proximal endopodal article of the uropod, in addition to two stout spines each with a subdistal sensilla. In both other genera the medial armature of this article comprises only stout spines with subdistal sensillae; the row of spinules is absent. Finally, the new genus has vestigial exopods on P5 and P6, whereas the exopods of these limbs are well developed in the other two genera.

Additional differences from Hirsutia include the biramous condition of the first pereopod (exopod absent in Hirsutia ); the medial armature of the carpus of P2 comprising only three barbed spines (5–6 barbed spines in Hirsutia ); and the armature of telson, which lacks the two stout dorso-distal serrate spines at this position in Hirsutia . In addition, Montucaris gen. nov. does not express the intersegmental articulation between basis and ischium in P3, P4 and P5. The articulation is expressed in both P3 and P 4 in H. bathyalis ; but P3 and P4 are unknown in H. sandersetalia .

Additional differences from Thetispelecaris include the filiform extension of the paragnaths, which are smooth in Montucaris but setulose in Thetispelecaris ; and the condition of female PL 4–5, which are not articulated proximally to the body in Montucaris whereas they are articulated in Thetispelecaris .