SPBN Graening, Fenolio & Harris Speleobiology Notes 7: 11–17 11 The subterranean fauna of the Arbuckle Mountains Ecoregion of Oklahoma, USA Gary O. Graening 1 , Danté B. Fenolio 2 & Keith A. Harris 3 1 Department of Biological Sciences, California State University, Sacramento, 6000 J Street, Sacramento, CA 95819-6077, USA graening@csus.edu (corresponding author) 2 Department of Conservation and Research, San Antonio Zoo, 3903 N. St. Mary’s Street, San Antonio, TX 78212, USA dantefenolio@sazoo.org 3 Tulsa Regional Oklahoma Grotto, National Speleological Society, 2813 Cave Avenue, Huntsville, AL 35810, USA harrisk1@cox.net Key Words: Allocrangonyx pellucidus, amphipod, Arbuckle Mountains ecoregion, Asellidae, biodiversity, Caecidotea acuticarpa, Chaetaspis, Crosbyella, Desmoniella curta, Etheostoma microperca, isopod, Macrosternodesmidae, Miktoniscus oklahomensis, Oklahoma, Phalangodidae, Sphaeriodesmidae, stygobiotic, Stygobromus alabamensis, range extension, new record, Trichoniscidae, troglobiotic. The Arbuckle Mountain Uplift, and the Arbuckle Plains to a lesser extent, hosts an impressive density of caves in karstified limestone formations (e.g., West Spring Creek and Kindblade) of the Ordovician Period. These caves serve as karst windows into the extremely deep and productive Arbuckle-Simpson Aquifer (Graening et al. 2011). The fauna found within subterranean habitats within the Arbuckle Mountains Ecoregion of Oklahoma (Carter, Coal, Johnston, Murray, and Pontotoc counties) were investigated as part of a larger bioinventory program (Graening et al. 2008; Graening et al. 2011). Previous studies of subterranean habitats in or near this ecoregion include Creaser and Ortenberger (1933), Mackin (1935), Mackin and Hubricht (1940), Hall (1956), Chamberlin and Hoffman (1958), Harrel (1960, 1963), Vandel (1965, 1977), Black (1971, 1973, 1974), Holsinger (1971, 1989), Fleming (1972), McKinley et al. (1972), Reisen (1975), Matthews et al. (1983), Vaughn (1996), Gaskin and Bass (2000), Lewis (2002), The Nature Conservancy (2004), Graening et al. (2006, 2007), and Lewis et al. (2006). Eight obligate subterranean species have been documented from the karst of the Arbuckle Mountains Ecoregion.  Oklahoma Cave Amphipod Allocrangonyx pellucidus (Mackin, 1935) (Allocrangonyctidae) (Figure 1): endemic to the Arbuckle Uplift and Plains in four springs in Johnston County, three caves and six springs in Murray County, and