PHYLOGENY OF ARIETELLID COPEPODS 



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Fig. 37. Pilarella longicornis , female (paratype). A, Genital double-somite, ventral view; B, Apical endopod segment of antenna; C, 

 Praecoxal arthrite of maxillule; D, Maxillulary endopod; E, Praecoxal endites of maxilla; F, Tip of endopod of maxilliped showing setae a 

 and b. Scales in mm. 



somite in almost all arietellids. Re-examination of those taxa 

 in which the cephalosome and the first pedigerous somite 

 were previously reported to be fused (for example, Paraugap- 

 tilus magnus), has revealed that these somites are clearly 

 separate. In Metacalanus species 1 the cephalosome is weakly 

 fused with the first pedigerous somite ventrolaterally. In all 



arietellids the fourth and fifth pedigerous somites are invari- 

 ably fused, with or without a suture. 



Within the genus Arietellus, A. setosus has a well- 

 developed cephalic projection, a pair of strong ventrolateral 

 processes on the last prosomal somite and a posteriorly 

 swollen caudal ramus with remarkably elongate setae. In 



