SYSTEMATICS AND PHYLOGENY OF ZAUSODES 



107 



P4 (Fig. 23F) exp-3 with 3 outer bipinnate spines. 



P5 (Figs 25D-E) baseoendopods fused medially forming trans- 

 versely elongate plate; each side with 2 bipinnate setae, slender 

 outer basal seta arising from cylindrical process, and spinules 

 around articulation with exopod. Exopod 1.2 times as long as wide 

 (excluding setae), with an additional pinnate seta along the outer 

 margin not found in 9 , and with fewer spinular rows. 



P6 (Fig. 25C) symmetrical; with distal seta; located more laterally 

 than in 9. 



ETYMOLOGY. Named in memory of Roy Cook and in honour of 

 Jessie Cook, the first author's grandparents. 



Mucropedia kirstenae sp. nov. 



Type LOCALITY. Gulf of Mexico: 29°40.63'N, 84°22.80'W, north- 

 ern Gulf of Mexico, 18 m depth, unvegetated medium sand; see 

 Thistle et al. (1995) for additional description. 



Material examined. 



The Natural History Museum: holotype9in alcohol (BMNH 

 1999.208); allotypic paratypecfin alcohol (BMNH 1999.209); other 

 paratypes are 19and lcfin ethanol (BMNH 1999.210-211) and 

 29 9and 2o"cfon slides (BMNH 1999.212-215). 



National Museum of Natural History (Smithsonian Institution, 

 Washington, D.C.): additional paratypes represented by 2 9 9and 

 2cfcfin alcohol (USNM 288456-457) and 19 and lcfon slides 

 (USNM 288454-455). 



Description. All illustrations are from paratypes except Figs 

 26A-B, which are from the holotype. 



Female. Body length: measured from anterior margin of rostrum 

 to posterior margin of caudal rami: 340 urn (x = 320 urn, n = 4); 

 without rostrum and caudal rami: 295 um (x = 276 um, n - 4). Body 

 (Figs 26A-B, 27B-C) dorsoventrally flattened. Greatest width: 

 153 um (x = 156 um. n = 4) near posterior margin of cephalosome. 

 Sensillae present on cephalothorax, pedigerous somites, and third, 

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

 cephalic shield with sensillae. Epimera of pedigerous somites thickly 

 chitinized laterally. Free thoracic somites and urosomites 1-5 with 

 fine spinular rows dorsally and dorsolaterally; penultimate somite 

 with ventral spinular row; anal somite with spinular rows ventrally 

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

 second pedigerous somites with 3 sensillae; third one with 2 sensillae. 

 Ventral posterolateral corners of urosomites 3-5 and lateral margins 

 of urosomites 1-4 with spinules. Genital double-somite with con- 

 tinuous chitinous internal rib ventrolaterally and ventrally (but not 

 dorsally). Anal somite cleft medially; anus located terminally, 

 triradiate, bordered by incised frill that is exposed in dorsal and 

 ventral aspects; with two ventral pores near posterior margin; anal 

 operculum and pronounced pseudoperculum present. Caudal rami 

 (Figs 26A-B, 27B-C) approximately wider than long, with 7 setae: 

 setae I — III bare, setae IV-V bipinnate, seta VI bipinnate, dorsal seta 

 (VII) carried on a Particulate socle. Gelatinous string extending 

 posteriorly from each caudal ramus not observed in specimens. 



Rostrum (Fig. 26C) 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. 27A) 8-segmented; segments 1 and 2 longest; 

 first segment widest with spinules; segment 4 with aesthetasc (60 

 Um long) ;setal formula: l-[l],2-[10],3-[9],4-[4 + (l+ae)],5-[2], 

 6-[4], 7-[4], 8-[5 + acrothek]; apical acrothek consisting of 2 setae 

 and 1 aesthetasc. 



Antenna (Fig. 28A). Coxa short and unornamented; allobasis 



with spinular row, abexopodal seta, and incomplete surface suture 

 marking original segment boundary between basis and first endopod 

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

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

 and 4 geniculate spines, one of which bearing spinules proximal to 

 geniculation and fused at base to a slender seta; with hyaline surface 

 frill as indicated in Fig. 28A; 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. 28B). 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. 28C). 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. 28E). Syncoxa with 3 endites; praecoxal endite with 



1 pinnate and 3 bare setae; proximal coxal endite with 1 bare seta and 



2 pinnate setae; distal coxal endite with 2 bare setae and 1 pinnate 

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

 segmented with 5 bare setae. 



Maxilliped (Fig. 28D). Syncoxa with a bipinnate seta and numer- 

 ous spinular rows as indicated in Fig. 28D; basis with a row of fine 

 spinules and seta along palmar margin; endopod represented by 

 acutely recurved claw with a proximal accessory seta. 



PI (Fig. 29E). Rami prehensile; coxa with spinular row along 

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

 near 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, 0.9 times as long as endopod (excluding apical elements); 

 exp-1 with subdistal bipinnate seta and spinular rows along outer 

 margin; exp-2 elongate, 2.3 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 incorpo- 

 rated 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 29B-C, 30A) with 3-segmented rami. Coxae with 

 spinular rows at outer distal corner of P2 and P4 and pore at inner 

 distal corner of P3 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 P2 enp-3, P3 enp-3 and P4 exp-2-3 and enp-3. 

 Pores present as illustrated (Figs 29B-C, 30A). Seta and spine 

 formula of P2-P4 as in Table 1 . 



P5 (Figs 30B-C) not fused medially. Baseoendopod with anterior 

 surface and marginal spinular rows; with 4 long, bipinnate and 1 

 short, bare 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 27B-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. 



