PHYLOGENY OF ARIETELLID COPEPODS 



143 



Fig. 25. Metacalanus sp. 1, female (A); Metacalanus sp. 2, female (B). SEM micrographs of mouthparts. A. Detail of segments IV to VIII 

 of antennary exopod, scale bar = 10 u.m; B, Mandibular endopod, indicated by arrow, scale bar = 5 u.m. 



Metacalanus species 2 (Figs 21A,24,25B,26H) 



Material examined. 4$$- 



Body length. 0.84, 0.84, 0.86, 0.88 mm. 



Description. Female. Cephalosome separate from first 

 pedigerous somite. Lateral lobe of last prosomal somite 

 produced backwards reaching halfway along second urosomal 

 somite (Fig. 24A). Genital double-somite (Figs 21A,24A) 

 wider than long, symmetrical, with paired gonopores and 

 copulatory pores located ventrolaterally near posterior end of 

 somite; each gonopore lacking outer cuticular lateral flap 

 found in M. species 1, anterior half opening, covered by oval 

 flap; copulatory pore (Fig. 24C,D) small, round, ca. 1.4 |xm 

 in diameter, located near anterior inner corner of gonopore 

 (spermatophore remnant attached to opening). Internal geni- 

 tal system similar to that of M. species 1. Anal operculum 

 triangular as in M. species 1. 



Antennule asymmetrical, left longer than right, different in 

 fusion pattern and armature (see Fig. 22). Right antennule: 

 segments X to XI, and XIV and XV only partly fused near 

 posterior margin; fusion pattern and armature as follows: 

 I-VI-12 + 2 aesthetascs (1-3 + aesthetasc, II— 1, III-2 + 

 aesthetasc, IV-2, V-2, VI-2), VII-1 + aesthetasc, VIII-1, 

 IX-X-3 + aesthetasc (IX-1 + aesthetasc, X-2), XI-2 + 

 aesthetasc, XII-2 + aesthetasc, XIII-1 + aesthetasc, XIV-2 

 + aesthetasc, XV-2 + aesthetasc, XVI-2 + aesthetasc, 

 XVII-2 + aesthetasc, XVIII-2 + aesthetasc, XIX-2 + 

 aesthetasc, XX-1 + aesthetasc, XXI-2 + aesthetasc, 

 XXII-1, XXIII-1, XXIV-XXVIII-12 + 2 aesthetascs 

 (XXIV-1 + 1, XXV-1 + 1 + aesthetasc, XXVI-XXVIII-8 + 

 aesthetasc). Left antennule: segments X and XI partly fused 

 near posterior margin; suture between segments XI and XII 

 visible on both surfaces, XII and XIII only on one surface, 



XIII and XIV completely fused; fusion pattern and armature 

 as follows: I-V-10 + 2 aesthetascs (1-3 + aesthetasc, II— 1 , 

 III— 2 + aesthetasc, IV-2, V-2), VI-2, VII-1 + aesthetasc, 

 VIII-1, IX-X-3 + aesthetasc (IX-1 + aesthetasc, X-2), 

 XI-XIV-7 + 2 aesthetascs (XI-2 + aesthetasc, XII-2, 

 XIII-1, XIV-2 + aesthetasc), XV-2 + aesthetasc, XVI-2 + 

 aesthetasc, XVII-2 + aesthetasc, XVIII-2 + aesthetasc, 

 XIX-2 -I- aesthetasc, XX-2 + aesthetasc, XXI-2 + aes- 

 thetasc, XXII-1, XXIII-1, XXIV-XXVIII-12 + 2 aes- 

 thetascs (XXIV-1 + 1, XXV-1 + 1 + aesthetasc, 

 XXVI-XXVIII-8 + aesthetasc). 



Antenna with same segmentation and setation as M. spe- 

 cies 1. Mandibular palp: endopod (Fig. 25B) rudimentary, 

 1-segmented, with 1 plumose seta; exopod with setation as in 

 M. species 1. Maxillule: praecoxal arthrite without elements; 

 coxal endite with short seta; coxal epipodite with 5 setae; no 

 basal seta; endopod represented by small, unarmed knob. 

 Maxilla and maxilliped as in M. species 1. 



Legs 1 to 4 with same segmentation and setation as M. sp. 

 1. Leg 5 (Fig. 26H): coxae separate from intercoxal sclerite; 

 right basal seta thicker than left; endopod absent; right and 

 left exopods each 1-segmented, bulbous, with spiniform seta 

 terminally. 



Remarks. The fifth leg of this as yet undescribed species 

 resembles that of M. curvirostris but it can be distinguished 

 from the latter by the smaller body, the longer antennules, 

 and by differences in the mouthparts. 



Genus Paraugaptilus Wolfenden, 1904 



Diagnosis (emended). Female. Body relatively large, mea- 

 suring about 3 mm in total length. Prosome: cephalosome 

 narrowed anteriorly, separate from or weakly fused with first 



