Heel of extended hind limb falls considerably short of snout tip (Stejneger 1893). Tympanic disc has vertical diameter greater than the distance between the nostrils and eye (Stejneger 1893). Vomerine teeth between choanae and projecting beyond choanae posteriorly (Stejneger 1893). Hind feet about 2/3 webbed (Stejneger 1893). Single small metatarsal tubercle (Stejneger 1893). Paired weak dorsolateral ridges, and lacking longitudinal folds between the dorsolateral ridges (Stejneger 1893). Skin is granular on posterior lower aspect of femur (Stejneger 1893). Dorsum and flanks with numerous small dark spots "surrounded by lighter" (Stejneger 1893). No black ear patch (Stejneger 1893). Although Stejneger (1893) stated that external vocal sacs were not present, Wright and Wright (1949) report the presence of vocal sacs both from field experience with live frogs and from preserved specimens.
Olive green ground color, sometimes with the anterior body a brighter green, and with dark greenish olive to green spots. Spots often reduced or indistinct on anterior body/head, especially in males. Light stripes along dorsolateral folds. Throat light green with some pinkish suffusion, clouded with dark grayish olive green. Chest and belly may have pinkish cinnamon and may be clouded like the throat. Ventral surfaces of hindlimbs honey yellow to chamois. Males have nuptial pads. Females have more spotting dorsally than males (Wright and Wright 1949, from 1925 field notes on Tule Springs specimens, collected about 16 miles from what was Las Vegas at the time). Linsdale (1940) notes that R. fisheri had a "peculiar shade of ground color" compared to R. pipiens, but the shade is not otherwise described by that author.
Holotype USNM 18957 (adult female) was collected on March 13, 1891 (Jennings 1988). Specimens collected at Vegas Valley in 1891 are at USNM (HerpNET); specimens are also present in the MVZ, Stanford and California Academy of Sciences collections (Wright and Wright 1949), and at LACM (HerpNET).
This taxon has been treated as Rana fisheri (Stejneger 1893; Jennings et al. 1995) and as synonymous with (Slevin 1928) or a subspecies of R. onca (Jennings 1988; Stebbins 2003). Linsdale (1940) and Jennings et al. (1995) suggested on the basis of morphological analysis that R. fisheri was in fact a distinct species and not a subspecies of R. onca.
Hillis and Wilcox (2005) also noted that populations of leopard frogs (characterized as R. chiricahuensis) from the Mogollon Rim, Arizona, may be referrable to R. fisheri, based on morphological similarity.
In 2011, Hekkala and colleagues used ancient DNA methods with frogs fixed in ethanol in 1915 and preserved at the California Academy of Sciences to show that samples of R. fisheri cluster within the northwestern clade (of two clades currently assigned to Rana chiricahuensis), and they have assigned members of that clade (mainly from the Mogollon Rim region) to R. fisheri. The status of the second clade, currently R. chiricahuensis, is now in question, especially important given recent focus on conservation efforts.
- Wright, A. H. and Wright, A. A. (1949). Handbook of Frogs and Toads of the United States and Canada. Comstock Publishing Company, Inc., Ithaca, New York.
- Stuart, S., Hoffmann, M., Chanson, J., Cox, N., Berridge, R., Ramani, P., and Young, B. (eds) (2008). Threatened Amphibians of the World. Lynx Edicions, IUCN, and Conservation International, Barcelona, Spain; Gland, Switzerland; and Arlington, Virginia, USA.
- Stebbins, R. C. (2003). Western Reptiles and Amphibians, Third Edition. Houghton Mifflin, Boston.
- HIllis, D. M., and Wilcox, T. P. (2005). ''Phylogeny of the New World true frogs (Rana).'' Molecular Phylogenetics and Evolution, 34, 299-314.
- Hekkala, E.R., Saumure, R.A., Jaeger, J.R., Herrmann, H-W., Sredl, M.J., Bradford, D.F., Drabeck, D., and Blum, M.J. (2011). ''Resurrecting an extinct species: archival DNA, taxonomy, and conservation of the Vegas Valley leopard frog.'' Conservation Genetics, published online 28 May 2011.
- Jennings, M. R. (1988). ''Rana onca Cope, relict leopard frog.'' Catalogue of American Amphibians and Reptiles. American Society of Ichthyologists and Herpetologists, 417.1-417.2.
- Jennings, M. R. and Hayes, M. P. (1994). ''Decline of native ranid frogs in the desert southwest.'' Herpetology of the North American Deserts, Special Publication, Number 5. P. R. Brown and J. W. Wright (Eds.), eds., Southwestern Herpetologists Society, Van Nuys, California.
- Jennings, R. D., Riddle, B. R. and Bradford, D. (1995). ''Rediscovery of Rana onca, the relict leopard frog, in southern Nevada with comments on the systematic relationships of some leopard frogs (Rana pipiens complex) and the status of populations along the Virgin River.'' Report prepared for Arizona Game and Fish Dept., U.S. Bureau of Land Management, Las Vegas Valley Water District, U.S. National Park Service, and Southwest Parks and Monuments Association. 73 pp.
- Linsdale, J. M. (1940). ''Amphibians and reptiles in Nevada.'' Proceedings of the American Academy of Arts and Sciences, 73(8), 197-257.
- Slevin, J.R. (1928). "The amphibians of western North America." Occasional Papers of the California Academy of Sciences, 16, 1-152.