Distribution.—The composite range of the Middle American frogs of the Hyla microcephala group includes the lowlands of southern México and Central America, in some places to elevations of 1200 meters, southeastward from southern Jalisco and southern Veracruz, excluding arid regions (northern Yucatán Peninsula, Balsas-Tepalcatepec Basin, Plains of Tehuantepec, Grijalva Valley, Salamá Basin, and upper Motagua Valley) to the Pacific lowlands and the Cauca and Magdalena valleys in Colombia.
Key to Species and Subspecies
| 1. | Lateral dark stripe, bordered above by narrow white line, extending from snout at least to sacral region2 |
| Lateral dark stripe, if present, not extending posteriorly to sacral region and not bordered above by narrow white line4 | |
| 2. | Lateral dark stripe continuous to groin; dark flecks or longitudinal line on shanks; interorbital dark bar absent; dorsal pattern usually consisting of pair of longitudinal dark lines or series of dashes3 |
| Lateral dark stripe usually extending only to sacral region; dark transverse bars on shanks; interorbital bar usually present; dorsal pattern usually consisting of interconnecting dark lines, sometimes forming transverse marksH. microcephala underwoodi | |
| 3. | Lateral dark stripe narrow, covering only upper edge of tympanum; dorsal longitudinal stripes continuous, extending to ventH. microcephala microcephala |
| Lateral dark stripe wide, encompassing entire tympanum; dorsal markings consisting of longitudinal series of flecks or dashes, or of two lines, usually not extending to vent H. robertmertensi | |
| 4. | Lateral dark stripe indistinct, present only above tympanum and insertion of arm; dorsal markings consisting of narrow lines and dashes, sometimes interconnected; transverse bars on shanks narrow relative to interspacesH. phlebodes |
| Lateral dark stripe absent; dorsal markings consisting of two broad chevron-shaped marks; transverse bars on shanks wide relative to interspacesH. sartori | |
ACCOUNTS OF SPECIES AND SUBSPECIES
Hyla microcephala Cope
Diagnosis.—Lateral dark stripe narrow, covering only upper edge of tympanum, bordered above by narrow white stripe; dorsal pattern consisting of pair of longitudinal brown lines and no interorbital bar (eastern populations), or of irregular dark markings forming an X- or )(-shaped mark in scapular region and an interorbital bar (western populations).
Content.—The populations inhabiting the Pacific lowlands of southeastern Costa Rica eastward to Colombia are recognized herein as Hyla microcephala microcephala Cope; the populations in western Costa Rica northward to México are assigned to Hyla microcephala underwoodi Boulenger.
Distribution.—Southern Veracruz and northern Oaxaca southeastward through the Atlantic lowlands of Central America to north-central Nicaragua, thence southeastward on the Pacific lowlands to eastern Panamá, and thence into the Cauca and Magdalena valleys (Caribbean drainage) of Colombia ([Fig. 1]).