Bush inhabitants include several species of lizards and snakes, all of which have rather elongate, slender bodies, and long tails. Common bush-inhabitants in southern El Petén are Anolis limifrons rodriguezi, Basiliscus vittatus, Laemanctus deborrei, Leptophis mexicanus mexicanus, and Oxybelis aeneus aeneus. All of these are diurnal, and all but Laemanctus have been observed sleeping on bushes at night.
Tree-trunk inhabitants include five species of lizards. Thecadactylus rapicaudus lives on the trunks of large trees; Sphaerodactylus lineolatus lives beneath the bark on dead trees and on corozo palms. Anolis lemurinus bourgeaei lives on the bases and buttresses of large trees, from which it often descends to the ground. Corythophanes cristatus and Anolis capito were found only on tree trunks and large vines.
The least information is available for the species living in the tree tops. The following species were obtained from tops of trees when they were felled, or have been observed living in the tree tops: Anolis biporcatus, Iguana iguana rhinolopha, Celestus rozellae, Leptodeira septentrionalis polysticta, Leptophis ahaetulla praestans, Sibon dimidiata dimidiata, and Sibon nebulata nebulata.
Epiphytes, especially the bromeliads, provide refuge for a variety of tree frogs and small snakes. Of the tree frogs, Hyla picta, Hyla staufferi, Phyllomedusa callidryas taylori, Similisca baudini, and Similisca phaeota cyanosticta have been found in bromeliads; other species probably occur there. Among the snakes, Imantodes cenchoa leucomelas, Leptodeira frenata malleisi, Leptodeira septentrionalis polysticta, Sibon dimidiata dimidiata, and Sibon nebulata nebulata are frequent inhabitants of bromeliads; all of these snakes are nocturnal.
[Relationships of the Fauna]
Most of the 78 species of amphibians and reptiles definitely known from the rainforest in southern El Petén have extensive ranges in the Atlantic lowlands of southern México and Central America; many extend into South America. Sixty-two (80%) of the species belong to this group having extensive ranges in Middle America. Three species (Syrrhophus leprus, Leptodeira frenata, and Kinosternon acutum) are at the southern limits of their distributions in southern El Petén and northern Alta Verapaz, whereas Eleutherodactylus rostralis and Thecadactylus rapicaudus are at the northern and western limits of their distributions in El Petén. Nine (11%) species have the center of their distributions in El Petén and the Yucatán Peninsula; representatives of this group include Claudius angustatus, Dermatemys mawi, Laemanctus deborrei, and Eumeces schwartzei.
In determining a measure of faunal resemblance, I have departed from the formulae discussed by Simpson (1960) and have analyzed the degree of resemblance by the following formula used to calculate an index of faunal relationships:
C (2) / (N1 + N2) = R, where
C = species common to both faunas.
N1 = number of species in the first fauna.