The Amphibians and Reptiles of Sinaloa, Mexico - Smithsonian ...

AMPHIBIANS AND REPTILES OF SINALOA, MEXICO 97
from southern Sinaloa and are scattered, forming an indistinct pattern,
in frogs from northern Sinaloa; the flanks are pale ventrally
with a slight peppering of pigment or are faintly mottled with pale
brown.
The specimens from Sinaloa were compared with 20 specimens
from Sonora (20 to 50 kilometers east of Kino), and with 161 frogs
from Texas. The Sonoran specimens have brownish flanks; an indistinct
row of black spots borders the flanks dorsally and posterior
to the eye in some individuals, but spots are absent in others. The
brown inguinal spots seem slightly smaller, but darker and more
conspicuous, than those of the Sinaloan frogs. The limb bars are
either solid, composed of many fused dark brown spots, or reduced
to two to four dark brown spots. Dorsal brown spots are present
anteriorly, or they are absent. The belly is creamy white with the
edges, the chest, and lower jaw mottled with brown, or with a faint
peppering of dark pigment. The flanks are distinctly mottled with
brown.
The Texan frogs have small inguinal spots or lack them entirely.
The limb spots, if present, are small, brown to brownish black,
separated or fused, and enclose a pale tan area. The dark brown
lateral area that is present in frogs from Sinaloa may be absent or
indistinct. The dorsal spots are smaller and fewer than in Sonoran
frogs, or are absent. The belly is clear with only a trace of mottling
laterally. The flanks are unmarked or only faintly mottled.
From the characters of the pattern and coloration examined, it
is evident that the population in western Sonora differs from the
populations in Sinaloa and Texas in having distinctly mottled sides,
mottling on the lower jaw, chest, and edges of the belly, and distinct
dark brown inguinal and leg spots. Other characters are intermediate
between the Sinaloan and Texan populations.
Wake (1961:88-89), on the basis of specimens secured in southern
Arizona, elevated mazatlanensis to specific status on the assumption
that the single specimen reported by Hecht and Matalas (1946:4)
is a hybrid and does not represent an intergrading population. If
the specimen reported by Hecht and Matalas (1946:4) is a hybrid,
then the Sinaloan population would be G. mazatlanensis. Until
more material from eastern Sonora and western Chihuahua is available,
we refer the Sinaloan specimens to Gastrophryne olivacea
mazatlanensis. Regardless of the specific status of the frogs west
of the continental divide, those from northwestern coastal Sonora
possibly represent a taxon distinct from that in Sinaloa.