SYSTEM ATICS AND PHYLOGENY OF ZAUSODES 



113 



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

 posterior margin of caudal rami: 253 urn (x = 249 urn, n = 4); without 

 rostrum and caudal rami: 220 urn (x = 217 um, n = 4). Body width: 

 1 3 1 um (x = 1 34 um, n = 4). Not all sensillae shown in habitus views 

 (Figs 31 A-B). Sexual dimorphism in body size, rostrum (Fig. 31C), 

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

 segmentation (Figs 32B-C). 



Antennule (Fig. 32A) 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 

 (50 um long); with armature formula 1-[1], 2-[l], 3-[9], 4-[9], 5- 

 [8 + (l +ae)],6-[7]. 



P2 (Fig. 29A) as in 9 except for endopod. Enp- 1 with outer row of 

 spinules and anterior pore. Enp-2 with outer distal corner extending 

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

 inner margin with subdistal thick pinnate seta. Enp-3 with spinulose 

 outer margin, distal spinous apophysis, and 3 inner setae. 



P3 (Fig. 29D) enp-2 with outer distal corner produced into 

 apophysis; enp-3 without pore and posterior spinules found in 9 . 



P4 (Fig. 30D) exp-3 with 3 outer bipinnate spines. 



P5 (Figs 30E-F) 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 . 1 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. 32C) symmetrical; with distal seta; located more laterally 

 than in 9. 



Etymology. Named for Kirsten Lambshead. 



Notes. 



M. kirstenae can be readily distinguished from M. cookorum by the 

 segmentation of the P4 endopod (3-segmented in M. kirstenae, 2- 

 segmented in M. cookorum). Both species are extremely close 

 otherwise and additional differences should be sought at the level of 

 setal lengths and segmental proportions. It is the consistent nature of 

 these differences rather than their magnitude that convinced us of 

 the distinctiveness and co-occurrence of two species. The existence 

 of sibling species is a well known phenomenon in the family 

 Harpacticidae and makes accurate identification onerous. Soyer et 

 al. (1987) demonstrated the presence of sibling species of the genus 

 Tigriopus on the Kerguelen and Crozet Islands. Huys et al. (1996) 

 recently pointed out that Harpacticus obscurus T. Scott, H. 

 giesbrechti Klie and H. littoralis Sars are extremely difficult to 

 separate and identification is often based on setal lengths and 

 ornamentation, pore patterns and position of spinule rows. 



Genus Archizausodes gen. nov. 



Diagnosis. Harpacticidae. Antennule 9 8-segmented, without pin- 

 nate or plumose setae on segments 1-6; without strong, modified 

 spines on segments 3-5 or enlarged pectinate or pinnate spines on 

 segment 6. Antennulecfwithout modified spines on segment 3. 

 Antennary exopod 2-segmented, with armature formula [2, 2]. 

 Maxilla with 4 spines/setae on praecoxal endite. P2-P3 endopods 3- 

 segmented, P4 endopod 2-segmented. P2 9 enp-3 with 2 inner setae. 

 P3 9 enp-2 with inner seta. P4 exp-3 with 3 outer spines in both 

 sexes. P4 enp-2 with 2 inner setae in both sexes. P2cfenp-2 without 

 distinct apophysis, inner seta not modified; enp-3 with 1 apical seta 

 (inner one lost), outer spine fused to segment. P3c?enp-2 outer distal 

 corner not attenuated. 



Swimming leg setal formula: 



exopod 



endopod 



P2 



P3 

 P4 



0.1.223 



0.1.323 

 0.1.323 



0.1.221 [9] 

 0.1.211 [cf] 

 1.1.221 

 1.221 



P5 exopod elongate-oval in both sexes. P5 endopodal lobe 9 not 

 developed; distal 3 inner setae rudimentary. 



Sexual dimorphism in rostrum, antennule, P2 endopod, P5, P6, 

 genital segmentation and size. 



TYPE SPECIES. Zausodes biarticulatus Ito, 1979 = Archizausodes 

 biarticulatus (Ito, 1979) comb. nov. 



Other species. None. 



Etymology. The generic name is derived from the Greek prefix 

 archi-, meaning first, and alludes to the primitive position of the 

 genus. Gender: masculine. 



Archizausodes biarticulatus (Ito, 1979) comb. nov. 



TYPE LOCALITY. Chichi-jima Island, Bonin Islands; shallow water 

 off Miyanohama; coarse sand with broken shells and corals. 



NOTES. 



Additional autapomorphies for this genus include the elongate 

 proximal exopod segment of PI, the transversely prolonged basis of 

 P4, and the reduction of particular setae on the exopod and 

 baseoendopod of 9 P5. A. biarticulatus shows some similarities with 

 Z. cinctus (see below). 



PHYLOGENY 



Selection of outgroup 



Lang (1944, 1948) divided the Harpacticidae in two subfamilies, 

 Harpacticellinae and Zausodiinae, the names of which were later 

 corrected by Vervoort (1964) as Harpacticinae and Zausodinae, 

 respectively. The Zausodinae was proposed to accommodate Zaus, 

 Zausodes and Zausopsis, all of which have a strongly dorso- 

 ventrally depressed, more or less shield-shaped body with 

 completely developed pleurotergites on the pedigerous somites. 

 The Harpacticinae included Harpacticus, Tigriopus, Harpactic- 

 ella and Perissocope which according to Lang (1944, 1948) have 

 a body which is 'normal, elongate and not shield-shaped'. Two 

 more genera, Discoharpacticus Noodt and Paratigriopus Ito 

 have been added to the latter subfamily since (Noodt, 1954; Ito, 

 1969). 



Lang (1948: 355) remarked that Zausodes showed a certain 

 resemblance with Perissocope in the reduced swimming leg arma- 

 ture but nevertheless assigned more weight to the body form, 

 favouring a relationship with Zaus and Zausopsis. Since Zausodes 

 has a short PI exp-1, a well developed maxilliped and 2 setae on 

 thed"P5 baseoendopod he was of the opinion that the genus had 

 diverged early in the evolution of the Zausodinae. On the other hand 

 he expressed some doubts as to the relationships of Perissocope 

 since males were as yet unknown. 



