SYSTEMATICS AND PHYLOGENY OF ZAUSODES 



99 



National Museum of Natural History (Smithsonian Institution, 

 Washington, D.C): additional paratypes represented by 3 9 9 and 

 2a"cfin alcohol (USNM 288452^153) and 19and lcfon slides 



(USNM 2888450^51). 



Description. All illustrations are from paratypes except 19A-B 

 which are from the holotype. 



Female. Body length: measured from anterior margin of rostrum 

 to posterior margin of caudal rami: 288 um (x = 283 urn, n = 4); 

 without rostrum and caudal rami: 257 um (x = 246 um, n = 4). Body 

 (Figs 19A-B, 20B-C) dorsoventrally flattened. Greatest width: 

 144 um (x = 158 um, n = 4) near posterior margin of cephalosome. 

 Sensillae present on cephalothorax, pedigerous somites and first, 

 third, fourth, and sixth urosomites (not all shown). Ventrolateral 

 margin of cephalic shield with sensillae. Epimera of thoracic somites 

 thickly chitinized laterally. Free thoracic somites and urosomites 1- 

 5 with fine spinular rows dorsally and dorsolaterally; urosomite 5 

 with ventral spinular row; anal somite with spinular rows ventrally 

 and laterally on the posterior margin. Lateral margins of first and 

 second free thoracic somites with 3 sensillae; third free thoracic 

 somite with 2 sensillae. Ventral posterolateral corners of urosomites 

 3-5 and lateral margins of urosomites 1^ with spinules. Genital 

 double-somite with continuous chitinous internal rib ventrolaterally 

 and ventrally (but not dorsally). Anal somite cleft medially; anus 

 located terminally, triradiate, bordered by incised frill that is ex- 

 posed in dorsal and ventral aspects; with two ventral pores near 

 posterior margin; anal operculum and pronounced pseudoperculum 

 present. Caudal rami (Figs 19A-B, 20B-C) slightly wider than long, 

 with 7 setae: setae I — III bare, setae I V-V bipinnate, seta VI bipinnate. 

 dorsal seta (VII) carried on a Particulate socle. Gelatinous string 

 extending posteriorly from each caudal ramus present in some 

 specimens. 



Rostrum (Fig. 1 9C) prominent, lateral margins roughly parallel to 

 each other, defined at base; with two short sensillae anteriorly and 

 one sensilla near each mediolateral margin; with middorsal pore. 



Antennule (Fig. 20A) 8-segmented; segments 1 and 2 longest; 

 first segment widest with spinules; fourth segment with an aesthetasc 

 (50 um long); apical acrothek probably consisting of 2 setae and 1 

 aesthetasc, however, we were unable to distinguish which elements 

 were setae and which was an aesthetasc; with setal formula l-[ 1 ], 2- 

 [10], 3-[9], 4-[4 + (1 + ae)], 5-[2], 6-[4], 7-[4], 8-[4 + acrothek]. 



Antenna (Fig. 21 A). Coxa short and unomamented; allobasis 

 with spinular row, abexopodal seta, and surface suture marking 

 original segment boundary between basis and first endopod seg- 

 ment; free endopod 1 -segmented; lateral armature consisting of 1 

 long and 3 short setae; distal armature comprising 1 seta, 1 curved 

 spine, and 4 geniculate spines, one of which bearing spinules 

 proximal to geniculation and fused at base to a slender seta; with 

 spinules and hyaline surface frill as indicated in Fig. 21 A; exopod 2- 

 segmented, exp-1 with 1 lateral seta and 1 bipinnate distal seta and 

 exp-2 with 2 distal setae. 



Labrum well developed, not medially incised. 



Mandible ( Fig. 2 1 B ) . Gnathobase with pinnate seta at dorsal corner; 

 coxa with proximal row of spinules; palp biramous, comprising basis 

 and 1 -segmented exopod and endopod; basis produced transversely, 

 with proximal spinular row and 4 bipinnate setae; endopod with 2 

 lateral setae and 6 apical setae; exopod with 3 lateral setae, 3 distal 

 setae, and spinular rows subdistally and along outer margin. 



Maxillule (Fig. 21C). Praecoxa with spinular row along outer 

 edge and with arthrite bearing 8 spines around distal margin, 2 

 anterior surface setae, and posterior spinular row; coxal endite with 

 5 setae; basal endite with 6 setae; endopod with 3 distal setae; 

 exopod with 1 inner seta and 3 distal setae. 



Maxilla (Fig. 2 1 E). Syncoxa with 3 endites; praecoxal endite with 

 4 setae; coxal endites each with 2 bare setae and 1 pinnate seta; 

 allobasis with claw, 1 pinnate and 2 bare setae; endopod 1 -seg- 

 mented with 5 bare setae. 



Maxilliped(Fig. 2 ID). Syncoxa with a bipinnate seta and numer- 

 ous spinular rows as indicated in Fig. 2 ID; basis with a row of fine 

 spinules and seta at distal palmar margin; endopod represented by 

 acutely recurved claw with a proximal accessory seta. 



PI (Fig. 22C). Rami prehensile; coxa with spinular row along 

 outer margin and pore at inner distal corner; basis with bipinnate seta 

 proximal to mid-point of outer margin and spine at inner distal 

 corner; spinular rows present along inner and outer margins, and 

 around articulation with endopod; with pore near outer seta. Exopod 

 3-segmented, 1.1 times as long as endopod (excluding apical ele- 

 ments); exp- 1 with subdistal bipinnate seta and spinular rows along 

 outer margin; exp-2 elongate, 1.9 times as long as exp-1, with 

 slender inner seta distally and outer margin spinular row extending 

 to insertion of subdistal pinnate seta; exp-3 vestigial, largely incor- 

 porated into exp-2, with 2 geniculate spines and 2 claws. Endopod 

 2-segmented; enp- 1 elongate with subdistal pore; enp-2 0.3 times as 

 long as enp-1. bearing geniculate spine, claw, and short, slender 

 inner seta distally, with distal fan of fine spinules. 



P2-P4 (Figs 22A-B, 23C) with 3-segmented exopods and 3- (P2- 

 P3) or 2-segmented (P4) endopods. Coxae with spinular rows at 

 outer distal corner of P2 and P4. Bases with outer bipinnate spine 

 (P2) or bare seta (P3-P4), and spinules plus a pore at outer distal 

 corner. Endopods distinctly shorter than exopods. Spinular rows 

 present on posterior surface of P3 enp-3 and P4 exp-2-3 and enp-2. 

 Pores present as illustrated (Figs 22A-B, 23C). Seta and spine 

 formula of P2-P4 as in Table 1. 



P5 (Figs 23A-B) not fused medially. Baseoendopod with anterior 

 surface and marginal spinular rows; with 1 short, bare and 4 long, 

 bipinnate inner setae; outer basal seta slender and arising from 

 cylindrical process. Exopod 1.9 times as long as wide (excluding 

 distal spines) with numerous anterior, posterior, and marginal spinular 

 rows; with 1 inner. 1 apical and 3 outer pinnate spines; posterior 

 surface with pore. 



Genital double-somite (Figs 20B-C) wider than long. Genital 

 field located far anteriorly. Copulatory pore large, midventral; lead- 

 ing via short copulatory duct to single median seminal receptacle. 

 Gonopores paired, closed off by opercula derived from vestigial 

 sixth legs bearing 3 naked setae. 



Male. Body length: measured from anterior margin of rostrum to 

 posterior margin of caudal rami: 225 um (x = 235 um, n = 4); without 

 rostrum and caudal rami: 194 um (x = 202 u.m, n = 4). Body width: 

 1 19 um(x= 126 um, n = 4). Not all sensillae shown in habitus views 

 (Figs 24A-B). Sexual dimorphism in body size, rostrum (Fig. 24C), 

 antennule, P2 endopod, P3 enp-2, P4 exp-3, P5, P6, and urosome 

 segmentation (Figs 25B-C). 



Antennule (Fig. 25A) 6-segmented, chirocer; aesthetasc-bearing 

 segment not conspicuously swollen; segment 3 longest; with 

 geniculation between segments 5 and 6. First segment with several 

 spinular rows along anterior margin; segment 5 with aesthetasc 

 (30 umlong); with armature formula l-[l],2-[l],3-[9],4-[9],5-[8 

 + (1 + ae)], 6-[4 +acrothek]. 



P2 (Fig. 22D) as in 9 except for endopod. Enp- 1 with outer row of 

 spinules. Enp-2 with outer distal corner extending to approximately 

 one third the length of enp-3; outer margin spinulose; inner margin 

 with subdistal stout pinnate seta. Enp-3 with spinulose outer margin, 

 distal spinous apophysis, and 3 inner setae. 



P3 (Fig. 22E) enp-2 with outer distal corner produced into apo- 

 physis. 



