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Holsinger, J.R. 1992. Four new species of subterranean amphipod crustaceans (Artesiidae, Hadziidae, Sebidae) from Texas, withcomments on their phylogenetic and biogeographic relationships. Texas Mem. Mus., Speleol. Monogr., 3:1-22.FOUR NEW SPECIES OF SUBTERRANEAN AMPHIPODCRUSTACEANS (ARTESIIDAE, HADZIIDAE, SEBIDAE) FROMTEXAS, WITH COMMENTS ON THEIR PHYLOGENETIC ANDBIOGEOGRAPHIC RELATIONSHIPSJohn R. HolsingerDepartment of Biological SciencesOld Dominion UniversityNorfolk, Virginia 23529ABSTRACTFour new stygobiont amphipod crustaceans are describedfrom a variety of groundwater habitats (e.g., caves, springs,interstitial media) in south-central and western Texas. The newspecies are Artesia welbourni (Artesiidae), Holsingeriussmaragdinus (Hadziidae), Mexiweckelia hardeni (Hadziidae),and Seborgia hershleri (Sebidae). The new locality records forArtesia in Culberson County, and Holsingerius and Seborgia inVal Verde County are the first for these genera outside theartesian well in San Marcos, Texas, whereas the new record forMexiweckelia in Medina County documents a significant rangeextension for this genus from north-central Mexico tosouth-central Texas. Seborgia relicta, previously described fromthe artesian well in San Marcos, is also newly recorded fromMedina County.Both the phylogenetic and biogeographic implications of thesenew taxa are discussed at some length because they providefurther insight into the origin and evolutionary biology ofstygobiont crustaceans in southern Texas and northern Mexico.INTRODUCTIONBy far the greatest taxonomic diversity of subterraneanamphipod crustaceans in North America isfound in Texas, primarily in groundwater habitats ofthe Edwards Aquifer and associated Balcones faultzone in the south-central part of the state. In themost recently published paper on Texas subterraneanamphipods (Holsinger and Longley, 1980), one newfamily, four new genera, and six new species weredescribed from an artesian well in San Marcos.Some of these species were also recorded fromnearby San Marcos Springs and deep artesian wellsnear San Antonio. Collecting of subterraneanamphipods in Texas has continued since this studywas published in 1980, resulting in many new localityrecords for previously described species and thediscovery of a significant number of taxa new to science.In this paper four of these newly discoveredspecies, all with close morphological affinities to thepreviously noted Edwards Aquifer well amphipodfauna, are described from subterranean groundwatersin Medina, Val Verde and Culberson counties.In addition, one species previously known onlyfrom the artesian well in San Marcos is recordedfrom Medina County.Descriptions of the four new species raise the totalnumber of stygobiont amphipods described fromTexas to 21. This remarkably diverse fauna encompassesrepresentatives of five families and nine genera.One of the new species belongs to the genusMexiweckelia, which was previously recorded from1