PHYLOGENY OF ARIETELLID COPEPODS 



169 



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Fig. 43. Schematic comparison of segmentation and setation of male fifth legs in the Arietellidae. The arrows indicate possible derivations of 

 setation and segmentation patterns and are not indicative of ancestor-descendant relationships between taxa. Ch: Crassarietellus huysi; Pp: 

 Paramisophria plaiysoma; Pm: Paraugaptiloides magnus; CI: Campaneria talipes; Ml: Metacalanus species 1; Ap: Arietellus plumifer; Pb: 

 Paraugaptilus buchani. C: Coxa; B: Basis; Is: Intercoxal sclerite; Ex: Exopod; En: Endopod. a-f,k: elements on exopod. Setae and spines 

 are not distinguished here. 



The intercoxal sclerite and both coxae are almost fused, 

 with the suture clearly visible in Crassarietellus and Campan- 

 eria, while in the other genera fusion is complete. The basis 

 and coxa are completely separate in both legs in Crassarietel- 

 lus, Campaneria, Paramisophria and Metacalanus, almost 

 completely fused in the right leg but completely separate in 

 the left leg in Paraugaptiloides, Arietellus and Paraugaptilus. 



Phylogenetic relationships between arietellid 

 genera 



Phylogenetic relationships between the 10 genera studied in 

 this paper were analyzed using PAUP 3.0 on a matrix of 44 

 characters (Tables 2,3)- The matrix contains a significant 

 proportion of missing data, shown in the matrix by a '9' 

 (Table 3). These missing data correspond to the unknown 

 males of the genera Scutogerulus, Sarsarietellus and Pilarella 

 and to the unknown females of Campaneria and Paraugapti- 

 loides. Since most of the characters used in the analysis are 

 sexually dimorphic (30 out of 44 characters), only a minority 

 of characters (14 of 44) can be scored for all taxa. The 

 phylogenetic scheme presented here is necessarily tentative, 

 subject to re-examination as the gaps in the data matrix are 

 filled by the discovery of unknown sexes. 



Four trees were generated by the analysis, all with the same 



statistics: tree length = 179; consistency index = 0.263; 

 homoplasy index = 0.737. These four trees differed only in 

 the relative positions of Campaneria, Paraugaptiloides and 

 Sarsarietellus. The relative positions of all other genera are 

 the same. All three of these genera are known from only one 

 sex. Tree 1 (Fig. 44) was selected as the best working 

 hypothesis of relationships because Campaneria was the first 

 offshoot of the Arietellus-group, as it was in three of the four 

 trees, and because it placed Sarsarietellus as an earlier 

 offshoot than Paraugaptiloides which we consider to be the 

 more apomorphic genus of the two. 



The genera of the Arietellidae form two lineages, the 

 Arietellus-group comprising six genera, and the Metacalanus- 

 group consisting of four genera. The Arietellus-group is 

 diagnosed by the apomorphic reduction of seta a on the 

 terminal segment of the maxillipedal endopod (character 27). 

 The Metacalanus-group lacks a simple diagnostic character. 

 The apomorphic state of character 38 (absence of endopod of 

 male right fifth leg) is found only within the group, in 

 Crassarietellus , Paramisophria and Metacalanus (the male of 

 Pilarella is unknown), and the apomorphic state of character 

 3 (asymmetrical antennules in females) is found only in 

 Paramisophria, Metacalanus and Pilarella. Crassarietellus 

 retains the plesiomorphic state. 



This analysis suggests that there may have been several 



