Centipede Subfamily Plutoniuminae 



105 



of P. zwierleini are identical to those in the eastern population of T. 

 posticus (compare Figs. 6 and 42 and Fig. 43 with Fig. 6 in Shelley 

 (1990a)). The legs lack dorsal or ventral spurs, and the segment possesses 

 a complete median dorsal suture and has rounded, nonextended coxopleurae. 

 The only detectable distinction between P. zwierleini and eastern forms 

 of T. posticus is the different number of spiracles. 



RELATIONSHIPS 



In assessing relationships among the plutoniuminine taxa, P. 

 zwierleini is obviously the sister-group to the five species of Theatops. 

 Within the latter, T. spinicaudus, which is unique in lacking a median 

 suture on the ultimate tergite, is the sister-group to the other four 

 species. Theatops phanus, with the dorsal prefemoral spur, is then 

 sister to the three species lacking this structure, and because T. posticus 

 and T. californiensis were once geographic races of a single species, 

 as shown by the residual intergrade specimens in the southwestern deserts 

 (Shelley, 1990a), T. erythrocephalus is sister to its American counterparts 

 (Fig. 44). Most of these proposed lineages cannot now be defined by 

 autapomorphies, and comparative biochemical investigations may be necessary 

 to elucidate such characters because of the high degree of phenotypic 

 similarity among the members of this subfamily. 



Their Holarctic distributions indicate a Laurasian origin for both 

 the subfamily and the genus Theatops. Aside from Plutonium and Theatops, 



Theatops 



R zwierleini 



spinicaunus 



phanus erythrocephalus posticus 



califomiensis 



Fig. 46. Relationships in the Plutoniuminae. 



