Comparisons.—Dixon (1957) recognized six species of Tomodactylus (nitidus, dilatus, albolabris, angustidigitorum, fuscus and grandis) in his revision of the genus. Another species (rufescens) was subsequently described by Duellman and Dixon (1959). Tomodactylus saxatilis differs from all the species named immediately above by the combination of characters given in the diagnosis. Tomodactylus saxatilis differs from nitidus, angustidigitorum and grandis in having the tips of the two outer fingers widened and truncate; saxatilis differs from dilatus, albolabris, fuscus and rufescens in having a smooth venter (not pustulate), a contrasting pale and dark marbled pattern on the back, and a lack of "flash" colors on the femora.
Tomodactylus saxatilis, having lumbar glands, also resembles three species referred to the genus Syrrhophus. Tomodactylus macrotympanum was described by Taylor (1940:496, 497) as having a large, moderately distinct lumbar gland; the species was referred to the genus Syrrhophus by Dixon (op. cit.:384). According to Firschein (1954:55), Syrrhophus smithi and S. petrophilus have elongate lumbar glands shaped like those in Tomodactylus. Tomodactylus saxatilis resembles macrotympanum, smithi and petrophilus more than it does other species; all four attain large maximal sizes, and have lumbar glands, mostly smooth ventral surfaces, three palmar tubercles (sometimes absent in saxatilis), and usually contrasting dorsal patterns (reduced to flecks and spots in all species except saxatilis). Tomodactylus saxatilis differs from macrotympanum in having an extensive marbled dorsal pattern and a small tympanum, and differs from smithi and petrophilus in having a marbled dorsal pattern and the tips of the outer two fingers widened and truncate. Tomodactylus saxatilis differs from all other named species of Syrrhophus in having conspicuous lumbar glands and in lacking inguinal glands.
Remarks.—The characteristics delimiting the genera Tomodactylus and Syrrhophus are not agreed upon by all workers (see discussions by Firschein, 1954:50; Langebartel and Shannon, 1956:164; and Dixon, 1957:383). I have referred saxatilis to the genus Tomodactylus on the basis of a lumbar gland, which was considered a distinguishing character for the genus by Smith and Taylor (1948:46) and Langebartel and Shannon (1956:165). Lumbar glands are longer than broad, at least one third the distance from axilla to groin, lateral and usually high, and often conspicuous and protuberant. The elevation or flatness of the lumbar glands seems to be due to individual variation; living specimens in the field had conspicuous and protuberant, or non-elevated, indistinct lumbar glands. Lumbar glands are not to be confused with inguinal glands, which are roundish, often yellowish, sometimes diffuse, lateral but low, often inconspicuous, and usually not protuberant. Inguinal glands occur in the genus Microbatrachylus and in some species of Eleutherodactylus, and have been described as flat, or low, or small, or indistinct for most species of Syrrhophus.
For financial assistance with field work I am grateful to Rollin H. Baker, and those individuals who administer the Michigan State University Development Fund and the Bache Fund of the National Academy of Sciences (Grant No. 463). I am grateful also to J. Keever Greer, Donald F. Switzenberg, and Rudolph A. Scheibner for aid in the field, to Edward H. Taylor, James R. Dixon, and William E. Duellman for profitable discussions, and to Thomas Sweringen for figure 1. The specific name alludes to the habitat (Latin, saxatilis = found among rocks).
LITERATURE CITED
Dixon, J. R.
1957. Geographic variation and distribution of the genus Tomodactylus in Mexico. Texas Journ. Sci., 9(4):379-409, 5 figs., 1 map, December.
Duellman, W. E., and Dixon, J. R.
1959. A new frog of the genus Tomodactylus from Michoacan, Mexico. Texas Journ. Sci., 11(1):78-82, 1 fig., 1 table, March.
Firschein, I. L.