SYSTEMATICS AND PHYLOGENY OF Z4 USODES 



81 



PI (Fig. 5C). Rami prehensile; coxa with spinular rows along 

 inner, outer, and distal margins and on anterior face, with pore at 

 inner distal corner; basis with bipinnate seta near mid-point of outer 

 margin and bipinnate spine at inner distal corner; spinular rows 

 present along inner and outer margins and around articulation with 

 endopod; with pore near outer proximal corner. Exopod 3-seg- 

 mented, 1.5 times as long as endopod (excluding apical elements); 

 exp- 1 with distal pinnate seta and spinular rows along outer margin; 

 exp-2 elongate, 2.6 times as long as exp- 1 , with short, slender inner 

 seta distally (arrowed) 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 outer spinular row; enp-2 0.2 

 times as long as enp-1, with outer spinular row and bearing genicu- 

 late spine, claw, and short, slender inr.jr seta distally. 



P2-P4 (Figs 4A-B, 5B) with 3-segmented rami. Coxae with 

 spinular rows at outer distal corner of P2-P3 and posteriorly near 

 outer edge of P4. Bases with outer bipinnate spine (P2) or naked 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-P4 exp-3, P4 exp- 1 and -2, P2-P4 enp-3. Outer distal 

 spine of P2-P4 exp-3 and P2 enp-3 tripinnate. Pores present as 

 illustrated (Figs 4A-B, 5B). Seta and spine formula of P2-P4 as in 

 Table 1. 



P5 (Figs 5A,D) biramous, not fused medially. Baseoendopod with 

 numerous anterior surface and marginal spinular rows; endopodal 

 lobe triangular, with 2 sparsely plumose and 2 short bare setae along 

 inner margin and 1 distally pinnate seta apically; 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 bipinnate spines, apical one with flagellate tip; posterior 

 surface with proximal pore near outer margin. 



Genital double somite (Figs 2C-D) wider than long. Genital field 

 located far anteriorly. Copulatory pore large, midventral; leading via 

 short copulatory duct to single median seminal receptacle. Gonopores 

 paired, closed off by opercula derived from vestigial sixth legs 

 bearing 2 naked setae. 



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

 posterior margin of caudal rami: 366 urn (x = 0.379 um, n = 4); 

 without rostrum and caudal rami: 294 urn (x = 338 um, n = 4). Body 

 width 147 um (x = 149 um, n = 4). Not all sensillae shown in habitus 

 views (Figs 6A-B). Sexual dimorphism in body size, rostrum, 

 antennule, P2 endopod, P5, P6, and urosome segmentation (Figs 

 7A-B). 



Rostrum (Fig. 6A) trapezoid, defined at base. 



Antennule (Figs 6C-D) 6-segmented, chirocer; segment 5 bear- 

 ing aesthetasc, not conspicuously swollen; segments 3 and 5 longest; 

 with geniculation between segments 5 and 6; first segment with 

 several spinular rows along anterior margin; with armature formula 

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



P2 (Fig. 7E) as in 9 except for endopod. Enp-1 with outer row of 

 spinules. Enp-2 with outer distal corner produced into spinous 

 apophysis, extending to distal margin of enp-3; outer margin 

 spinulose; inner margin with subdistal bipinnate seta. Enp-3 with 

 spinulose outer margin, short outer pinnate spine, long bipinnate 

 spine distally and 2 pinnate inner setae; with spinules on posterior 

 face and at bases of distal inner and apical elements. 



P5 (Figs 7C-D) biramous. Baseoendopods fused medially form- 

 ing transversely elongate plate; endopodal lobe slightly developed, 

 with 1 outer, distally pinnate seta and 1 inner, bipinnate seta; outer 

 basal seta slender and arising from cylindrical process; with spinules 



around articulation with exopods. Exopod as in 9 except for an 

 additional small, bipinnate seta along the outer margin, and fewer 

 spinular rows. 



P6 (Fig. 7B) symmetrical; with distal seta and spinules along 

 outer margin; located more laterally than in 9 . 



Notes. 



Wilson (1932) noted sexual dimorphism in the first pair of swim- 

 ming legs and the exopods of P3-P4 and further claimed that none 

 of the other rami was genuinely modified in the male. Lang (1965) 

 re-examined type specimens of Z. arenicolus and concluded that 

 neither PI nor P3-P4 displayed sexual dimorphism and that Wilson 

 had overlooked the modification of the male P2 endopod. 



Coull's (1971b) numerous records from the North Carolina shelf. 

 Bell & Woodin's (1984) record from Virginia, Bell's records from 

 Tampa Bay (e.g. Bell et ah, 1989), and this paper suggest that Z 

 arenicolus assumes a continuous distribution along the American 

 east coast from Massachusetts, around the Florida peninsula, and 

 into the northern Gulf of Mexico. 



Zausodes septimus Lang, 1 965 



TYPE LOCALITY. California, Monterey Bay, off Hopkins Marine 

 Station, about 7 m depth. 



Notes. 



The few disjunct records of this species suggest a wide distribution 

 both in the Caribbean and along the Pacific seaboard of the U.S. and 

 Latin America. Mielke (1990) found Z. septimus along both Pacific 

 and Caribbean coasts of Panama and subsequently recorded the 

 species also from Punta Morales in Costa Rica (Mielke, 1 997). Coull 

 (1971a) identified Z septimus from sediment samples taken on St. 

 Thomas (U.S. Virgin Islands). 



Mielke's (1990) specimens from Panama (particularly from the 

 Caribbean side; Isla Nalunega) are remarkably smaller than those 

 from the type locality in California but otherwise agree in most 

 aspects with Lang's (1965) description. Significant discrepancies 

 are found in ( 1 ) the shape of the rostrum which is squarish and 

 truncate in the Californian material but elongate bell-shaped and 

 pointed in Mielke's material, (2) the proportional lengths of the 

 antennulary segments in the 9 (particularly segments 3-4 are dis- 

 tinctly shorter in the Panama females), (3) the length of PI endopod 

 which is markedly shorter in Lang's specimens, and (4) the shape 

 and length of outer and apical spines of P2-P4 exp-3 which are 

 stouter and shorter in the Panama population. A further study based 

 on material from a wider range of localities is required to confirm 

 whether these differences originate from intraspecific variability as 

 Mielke (1990, 1997) advocates, or reflect the existence of two 

 closely related species. 



Z septimus can be differentiated from Z arenicolus by the 

 segmentation of the P4 endopod and by the shape of the P5 

 baseoendopod and the relative position of its setae. Males of both 

 species can be distinguished by their P2 endopod (i.e. enp-2 with 

 mucroniform process in Z arenicolus). 



Genus Neozausodes gen. nov. 



Lang (1965) remarked on the close similarity between Z sextus and 

 the three Brazilian species Z limigenus, Z. stammeri and Z 

 paranaguaensis. Geddes ( 1 968a) regarded Z areolatus as morpho- 

 logically closest to Z sextus. As a result of the phylogenetic analysis 

 these 5 species together with N. shulenbergeri sp. nov. are grouped 

 here in a new genus. 



