N₂ = number of species in the second fauna.

R = degree of relationships (when R = 1.00, the faunas are identical; when R = 0, the faunas are completely different).

The herpetofauna of southern El Petén has been compared with that in the Tikal-Uaxactún area (Stuart, 1958), that in the humid lowlands of Alta Verapaz (Stuart, 1950, plus additional data), and that in the Mexican state of Yucatán (Smith and Taylor, 1945, 1948, and 1950). The herpetofaunas of lowland Alta Verapaz and Yucatán are the largest, having respectively 94 and 91 species, where as there are 78 species known from southern El Petén and 64 from the Tikal-Uaxactún area. An analysis of faunal relationships (Table 2) shows that the faunas of the rainforests of southern El Petén and lowland Alta Verapaz are closely related. The relationships between these two areas and the Tikal-Uaxactún area in northern El Petén is notably less. Apparently the biggest faunal changes take place between southern El Petén and the Tikal-Uaxactún area, and between the latter and Yucatán. As stated by Stuart (1958:7) the Tikal-Uaxactún is transitional between the humid rainforests to the south and the dry outer end of the Yucatán Peninsula. The transitional nature of the environment is exemplified by a rather depauperate herpetofauna consisting of some species of both dry and humid environments and lacking a large fauna typical of either. Contrariwise, the continuity of the environment from southern El Petén to the lowlands of Alta Verapaz is reflected in degree of resemblance of the herpetofaunas.

Table 2.—Index of Faunal Relationships Between Southern El Petén and Other Regions.

Most of the species of amphibians and reptiles found in southern El Petén are found in humid tropical forests from the Isthmus of Tehuantepec southeastward on the Atlantic lowlands well into Central America.

ACCOUNTS OF SPECIES

In the following pages various aspects of the occurrence, life histories, ecology, and variation of the species of amphibians and reptiles known from southern El Petén are discussed. Only Cochranella fleischmanni reported by Stuart (1937) from Río Subín at Santa Teresa was not collected by us and is excluded. Because more worthwhile information was gathered for some species than others, the length and completeness of the accounts vary. All specimens listed are in the Museum of Natural History at the University of Kansas, to which institution all catalog numbers refer. Preceding the discussion of each species is an alphabetical list of localities from which specimens were obtained; numbers after a locality indicate the number of specimens obtained at each locality.

Bolitoglossa dofleini (Werner)