PHYLOGENY OF ARIETELLID COPEPODS 



145 



spinules along inner margin. Maxilliped: setal formula of 

 endopod 1,4,4,3,3,4; setae a and b on sixth endopod segment 

 reduced; seta c heavily chitinized, terminal inner spinules 

 fused to seta to form serrate margin. 



Third exopod segment of leg 1 with 2 outer spines. Leg 4 

 with minute inner coxal seta, in addition to basal seta. Leg 5 

 rudimentary, represented by a plate with proximal (basal) 

 seta and terminal or subterminal (endopod) seta. 



Male. Body as in female, measuring around 3 mm in 

 length. Left antennule 19-segmented; only first segment 

 fringed with setules along posterior margin; segments II and 

 III with seta; segment XIII with 2 setae; segment XXI and 

 XXII fused; compound segment XXIV-XXV with large 

 cuticular process; segment XXVI-XXVIII with 7 setae and 

 aesthetasc. 



Antenna: second endopod segment relatively shorter than 

 in female, with 1-2 setae medially; exopod indistinctly 6- or 

 7-segmented, segment VIII with or without seta, terminal 

 compound segment (IX-X) completely or incompletely fused 

 with segment VIII, bulbous, unarmed. Mandibular palp: first 

 exopod segment with well-developed seta. 



Leg 5: coxae fused with intercoxal sclerite; basis and coxa 

 separate in left leg and incompletely fused in right. Right leg: 

 endopod 1-segmented, rudimentary, unarmed; second exo- 

 pod segment expanded inwards, almost completely fused 

 with third to form compound segment, tapering distally, 

 carrying proximal seta and subterminal setule along outer 

 margin. Left leg: endopod 1-segmented, unarmed; exopod 

 3-segmented, last 2 segments almost fused, second exopod 

 segment swollen medially, third segment with 2 stout long, 

 outwardly-directed process terminally. 



Type SPECIES. Paraugaptilus buchani Wolfenden, 1904 

 (monotypic). 



Other species. P. similis A. Scott, 1909; P. meridionalis 

 Wolfenden, 1911; P. mozambicus Gaudy, 1965; P. archimedi 

 Gaudy, 1973; P. bermudensis Deevey, 1973; P. buchani sensu 

 Bradford, 1974. 



REMARKS. In P. bermudensis sexual dimorphism is exhibited 

 in the mouthparts and leg 1 (Deevey, 1973): second endopo- 

 dal segment of antenna carrying 1 short seta in female and 1 

 long plus 1 short seta in male, at midlength of the segment; 

 relative lengths of endopod and exopod of antenna; anten- 

 nary exopodal segment VIII unarmed in female, but bearing 

 long seta in male; first exopodal segment of mandible 

 unarmed (vestigial seta overlooked by Deevey (1973)) in 

 female but with well-developed seta in male; endopod of leg 1 

 indistinctly 3-segmented in female but distinctly in male. 

 Except for leg 1 the sexual dimorphism in P. bermudensis is 

 also found in P. similis (present study). 



Since the superfamily Arietelloidea Sars, 1902 generally 

 exhibits distinctly 3-segmented rami in legs 1-4 (Andronov, 

 1974; Park, 1986) and no other congeners show such fusion in 

 endopod of leg 1, the incomplete fusion of the endopodal 

 segments in the female seems to be autapomorphic in P. 

 bermudensis. P. buchani exhibits sexual dimorphism only in 

 the relative lengths of the antennary rami and in the setation 

 of the mandibular palp (Deevey, 1973; present study). 



Brodsky (1950) mentioned, in his definition of Paraugapti- 

 lus, that the left antennules of females are possibly longer 

 than the right, but P. similis has antennules of nearly equal 

 length (Scott, 1909; present study). 



Ecological note. Paraugaptilus is mainly distributed 

 within the upper 1000 m, in particular, between 500 and 1000 

 m depths (Deevey, 1973). The genus appears to be meso- and 

 bathypelagic. 



Paraugaptilus similis A. Scott, 1909 (Figs 27-30) 



Material examined. 9 and cf . 



Body length. $ 3.32 mm; cf 3.03 mm. 



Description. Female. Cephalosome separate from first 

 pedigerous somite. Genital double-somite (Figs 27A-C,28A) 

 asymmetrical, wider than long, swollen anteriorly, widest at 

 level of paired gonopores; each gonopore (Fig. 28B) covered 

 by operculum as in Arietellus, anterior half opening; copula- 

 tory pores remarkably asymmetrical, right pore located medi- 

 ally on right ventral side, slit-like, approximately 43 u.m in 

 length, left pore located ventromedially at about two-thirds 

 distance along double-somite, with round opening, about 27 

 u.m in diameter; both right and left copulatory ducts heavily 

 chitinized; right duct shorter than left, widest near pore 

 opening, constricted medially; left duct thick, with small 

 subchamber medially (see Fig. 27B); seminal receptacles 

 relatively small, right round in shape, left smaller than right, 

 spindle-shaped. 



Antennule (Fig. 27D) 20-segmented; seventh (X) to ninth 

 (XII) segments and 11th (XIV) and 12th (XV) segments only 

 partly fused near posterior margin; 20th (XXIII-XXV) and 

 21st (XXVI-XXVIII) incompletely fused with suture clearly 

 visible. Fusion pattern and armature as follows: I-IV-9 + 

 aesthetasc (1-3, II— 2, III— 2 + aesthetasc, IV-2), V-2 + 

 aesthetasc, VI-2, VII-2 + aesthetasc, VIII-2, IX-2, X-2, 

 XI-2 + aesthetasc, XII-2, XIII-2, XIV-2 + aesthetasc, 

 XV-2 + aesthetasc, XVI-2 + aesthetasc, XVII-2 + aes- 

 thetasc, XVIII-2 + aesthetasc, XIX-2 + aesthetasc, XX-2 + 

 aesthetasc, XXI-2 + aesthetasc, XXII-1, XXIII-XXVIII-12 

 + 2 aesthetascs (right), 12 + 3 aesthetascs (left) (XXIII-1, 

 XXIV-1 + 1, XXV-1 + 1 4- aesthetasc, XXVI-XXVIII-7 + 

 1 (right) or 2 (left) aesthetascs). First (I-IV) to seventh 

 segments fringed with long setules along posterior margin. 

 Posterior setae on segments XXV and XXVI having thicker 

 setules in right antennule than in left. 



Antenna: first endopod segment without inner mid-length 

 seta, second segment (Fig. 29B) about 1.8 times as long as 

 first segment, with 1 inner short seta, and 5 setae and vestigial 

 seta terminally; exopod (Fig. 29A) indistinctly 6-segmented, 

 sixth segment bulbous, unarmed; setal formula 0,1,1,1,1,0. 

 Mandibular palp (Fig. 29C): endopod absent; first exopod 

 segment carrying vestigial seta, fifth segment having 1 normal 

 and 1 reduced seta. Maxillule (Fig. 27E): praecoxal arthrite 

 with 5 spines, 2 of which serrate subterminally, ornamented 

 by minute spinules on both surfaces; coxal endite unarmed; 

 coxal epipodite with 8 setae; basal seta and endopod absent. 

 Maxilla: first praecoxal endite with 1 serrate seta and 1 

 vestigial element, second endite having single bipinnate seta 

 (Fig. 30A); basal spine (Fig. 29D) with 3 rows of spinules. 

 Maxilliped: fourth and fifth endopod segments (Fig. 27F) 

 each bearing unipinnate innermost seta, sixth segment (Fig. 

 27G) carrying reduced setae a and b, medium-length serrate 

 seta c whose tip chitinized, and elongate seta d with row of 

 sharp triangular spinules along inner margin. 



Leg 1: third exopod segment with 2 outer spines; endopod 

 distinctly 3-segmented. Leg 4: vestigial coxal seta present at 

 inner angle. Leg 5 (Fig. 30B): coxae, intercoxal sclerite, basis 



