Hyla microcephala Boulenger, Proc. Zool. Soc. London, p. 481, October 1, 1898 [Syntypes.—BMNH 94. 11. 1532-33 from Bebedero, Guanacaste Province, Costa Rica; C. F. Underwood collector] (not Hyla microcephala Cope, Proc. Amer. Philos. Soc., 23:281, February 11, 1886, from Chiriquí, Panamá).
Hyla underwoodi Boulenger, Ann. Mag. Nat. Hist., ser. 7, 3:277, April, 1899 (substitute name for Hyla microcephala Boulenger, preoccupied). Günther, Biologia-Centrali Americana, Reptilia and Batrachia, p. 278, September, 1901. Dunn and Emlen, Proc. Acad. Nat. Sci. Philadelphia, 84:25, March 22, 1932. Stuart, Misc. Publ. Mus. Zool., Univ. Michigan, 29:39, October 1, 1935. Taylor, Proc. Biol. Soc. Washington, 50:44, April 21, 1937. Stuart, Occas. Papers Mus. Zool., Univ. Michigan, 471:15, May 17, 1943. Taylor and Smith, Proc. U. S. Natl. Mus., 95:586, June 30, 1945. Stuart, Misc. Publ. Mus. Zool., Univ. Michigan, 69:35, June 12, 1948. Smith and Taylor, Bull. U. S. Natl. Mus., 194:85, June 17, 1948; Univ. Kansas Sci. Bull., 33:316, March 20, 1950. Stuart, Contr. Lab. Vert. Biol., Univ. Michigan, 45:48, May, 1950. Taylor, Univ. Kansas Sci. Bull., 35:891, July 1, 1952; Univ. Kansas Sci. Bull., 39:25, November 18, 1958.
Hyla phlebodes, Cole and Barbour, Bull. Mus. Comp. Zool., 50:154, November, 1906. Kellogg, Bull. U. S. Natl. Mus., 160:172, March 31, 1932.
Hyla microcephala martini Smith, Herpetologica, 7:187, December 31, 1951 [Holotype.—UIMNH 20965 from Encarnacion, Campeche, México; H. M. Smith collector]. Stuart, Contr. Lab. Vert. Biol., Univ. Michigan, 68:46, November, 1954. Fugler and Webb, Herpetologica, 13:105, July 10, 1957. Stuart, Contr. Lab. Vert. Biol., Univ. Michigan, 75:17, June, 1958. Neill and Allen, Publ. Research Div., Ross Allen's Reptile Inst., 2:26, November 10, 1959. Duellman, Univ. Kansas Publ., Mus. Nat. Hist., 13:62, August 16, 1960. Stuart, Herpetologica, 17:74, July 11, 1961. Hensley and Smith, Herpetologica, 18:70, April 9, 1962. Stuart, Misc. Publ. Mus. Zool., Univ. Michigan, 122:36, April 2, 1963. Holman and Birkenholz, Herpetologica, 19:144, July 3, 1963. Duellman, Univ. Kansas Publ., Mus. Nat. Hist., 15:225, October 4, 1963; Univ. Kansas Publ., Mus. Nat. Hist., 15:588, June 22, 1965.
Hyla microcephala underwoodi, Smith, Herpetologica, 7:188, December 31, 1951.
Diagnosis.—Brown lateral stripe narrow, extending to groin or only to sacral region, bordered above by narrow white line; dorsal pattern bold, consisting of X- or )(-shaped mark in scapular region or pair of interconnected dark lines on back; interorbital dark mark usually present; shanks usually having dark transverse bars.
Description and Variation.—The dorsal color pattern is highly variable. The various permutations of the X-shaped scapular mark and dark sacral marks differ proportionately in different samples. The variation in color pattern in 12 samples is summarized in [Table 2]. In samples from the southern part of the range (southern Nicaragua and Guanacaste Province, Costa Rica) more (40-93%) individuals have the lateral stripes extending to the groin than in northern samples (0-42%) from southern México and Guatemala. Likewise, the percentage of specimens lacking bars on the shanks and a dark interorbital bar is higher in the Costa Rican samples than elsewhere in the range. The X- or )(-shaped scapular markings and /\- or / \-shaped sacral markings are most prevalent in northern samples, whereas to the south the dorsal markings are more commonly arranged in a pattern of paired lines, which usually are discontinuous and usually extend posteriorly only to the sacral region. Thus, the color pattern in H. m. underwoodi in the southern part of its range shows trends towards the pattern characteristic of H. m. microcephala. Intergrades between these two subspecies have been discussed in the account of the nominate subspecies.
Table 2.--Variation in Color Pattern in Hyla microcephala underwoodi