The Chonaphini 195 



acicular (Montaphe + Tubaphe + Metaxycheir). Selenocheir, with its 

 short, plesiomorphic prefemoral process, represents a separate, sister 

 line. There are no intermediate forms with partly expanded prefemoral 

 processes or ones of intermediate lengths, an anatomical gap that 

 suggests age and the extinction of intermediate forms. Age is also 

 indicated by the substantial geographical gaps — between intraspecific 

 populations of both S. placidus and C. armata, between species of 

 Chonaphe, between Metaxycheir and Tubaphe, and most especially 

 between the western faunal regions and Semionellus. Chonaphe evexa 

 and schizoterminalis share an angular elevation on the dorsal face of 

 the prefemoral process distal to the shield, this being a low ridge in 

 the former and a laminate flap in the latter, and appear to be peripheral 

 relicts of an early lineage that has been supplanted by the younger 

 branch leading to C. armata and remissa, which possesses the thicker, 

 distal projection at the location of the ridge. Although evolving more 

 recently, the C. armata + remissa lineage is old enough to have undergone 

 substantial fragmentation, with lacunae between the populations of C. 

 armata. 



Regarding the forms with narrow, blade-like prefemoral processes, 

 the restricted distributions of Metaxycheir prolata and T. levii also 

 suggest age, and the former in particular seems to hold relict status 

 because it is known only from 4 samples and 6 adults despite inhabiting 

 the most heavily sampled area of Idaho. Montaphe elrodi, occupying 

 a broad, cohesive area in the western interior, evolved more recently, 

 and M. paraphoena, an enigmatic species, is a possible relict from an 

 intermediate line between the narrow, blade-like and expanded, laminate 

 forms. I am unable to resolve the relationships between these genera 

 and show an unresolved trichotomy in Figure 72. 



My overall impression of the Chonaphini is thus one of age. The 

 geographical and anatomical lacunae contrast markedly with the situa- 

 tions in the Eastern and Meso-American tribes Apheloriini, Nanariini, 

 Pachydesmini, and Rhysodesmini, which lack such gaps and evolved 

 more recently (Shelley and Whitehead 1986). The Chonaphini appears 

 to be the second oldest xystodesmid assemblage next to the Orophini, 

 which has an even larger geographical hiatus between its only nearctic 

 representative, Orophe, in Idaho and Montana, and the only other 

 known genera Pamelaphe and Kiulinga, in China (Hoffman 1964, 

 Shelley 1993^). Perhaps the Xystodesmidae, or more properly the 

 subfamily Xystodesminae, experimented at an early age with long, 

 twisted gonopodal telopodites and ones with long, slender, comparatively 

 simple acropodites and complex prefemoral processes, before settling 



