searchable PDF - Association for Mexican Cave Studies

of subterranean amphipod faunas of Texas andMexico.n has already been hypothesized that most of thenon-crangonyctid subterranean amphipods of Texasand Mexico (e.g., artesiids, bogidiellids, hadziids,sebids) as well as other groups of stygobiont crustaceans(such as cirolanid and stenasellid isopods, andthermosbaenaceans), originated from marine ancestorsthrough stranding in Late Cretaceous and/orearly Cenozoic times (Holsinger and Longley, 1980;Bowman, 1982; Holsinger, 1986b). The inland,freshwater stygobiont members of these groups occurat present in areas that were once covered byshallow marine embayments. The distribution patternsof the new taxa fall well within areas previouslysubjected to Cretaceous embayments, andtherefore offer further corroboration of the strandingtheory.The new locality for Artesia from Border Cave inCulberson County on the western fringe of the GreatPlains, approximately 650 km west of the only otherknown locality for this genus in San Marcos (Fig.11), is a significant range extension for this poorlyunderstood stygobiont group. However, consideringthe great distance and potential dispersal barriersbetween these widely separate localities, themorphological similarity of A. subterranea from theartesian well in San Marcos and A. welbourni fromBorder Cave is surprising.Border Cave is of further interest biogeographicallyfor subterranean amphipods because it isinhabited by an undescribed species of the hubbsigroup of Stygobromus. With one exception, thisgroup is restricted to far western United States andsouthwestern Canada (Holsinger and Shaw, 1986).In the southwestern United States only one otherspecies is recorded from southeastern Arizona, approximately500 km to the west of Border Cave.rII-_IP~COsTEXASEDWARDSPLATEAUBALCONES -----ESCARPMENT • AUSTIN" 1...• 0 SAN ANTONIO1GULFOFMEXICOoKM200 400Fig. 12.-Geographic distribution of HolsingerillS and Mexiweckelia in Texas and Mexico. Localities for Holsingerills indicated byopen circles: I, H. samacos (artesian well in San Marcos, Hays Co.); 2, H. smaragdimlS (Emerald Sink, Val Verde Co.). Localities forMexiweckelia indicated by closed circles: I, M. hardeni (Hondo Creek hyporheic, Medina Co.); 2, M. colei (Bolson de CuatroCienegas, Coahuila); 3, M. milchelli (Cueva de la Siquita, Durango).20