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

AMPHIBIANS AND REPTILES OF SINALOA, MEXICO 207
preoculars touch the frontal in three and the preoculars are separated
from the frontal in three; 21-24 (22,2) dorsal dark body
blotches (KU 78930 excluded); 9-11 (9.8) dorsal dark tail blotches
(KU 78930 excluded).
One male (KU 37592) has 21-22-17 dorsal scale rows; the head
is missing so no other counts are available. Characters of seven
additional males are as follows: ventrals, 243-249 (246.9); subcaudals,
81-87 (84.3) (KU 83416 excluded); dorsal scale rows at
neck, 21 in two, 22 in three, and 23 in two; scale rows at midbody,
23 in three, and 24 in four; scale rows at vent, 16 in one, 17 in two,
18 in three, and 19 in one; supralabials, 8-8 in one, 9-9 in five, and
9-10 in one; infralabials, 12-12 in three, and 13-13 in four; preoculars,
3-3 in seven; postoculars, 3-3 in six, and 4-3 in one; temporals,
2 + 3/3 + 3 in one, 3 + 3/3 + 4 in one, 3 + 4/3 + 4 in two,
3 + 3/3 + 3 in two, and 4 + 3/4 + 3 in one. Supralabials 4-5/4-5
enter the eye; the preoculars contact the frontal in one, the preoculars
do not contact the frontal in six. Dorsal dark body blotches,
17-25 (21.7), and dorsal dark tail blotches, 11-14 (12.0) (KU 80765,
83416 excluded).
A female and male from the vicinity of Badiraguato (KU 83415-
16) have more ventrals (251 and 248) than the intergrade reported
by Fouquette and Rossman (1963:198-99). Two of the specimens
examined from the southern half of Sinaloa (KU 73638, 80765) have
243 and 244 ventrals. If these specimens and one from 13 miles
north of the Sinaloa-Sonora state line (Dixon, Sabbath, and Worthington,
1962:98) are intergrades, then the zone of intergradation
would include most of Sinaloa northward from Mazatlan, as pointed
out by Davis and Dixon (1957a :24). A zone of intergradation
covering more than 500 kilometers is a condition untenable to most
biologists. Although we refer all Sinaloan specimens to T. I. paucimaculata
we recognize that clinal variation is probably a more
reasonable explanation of evolutionary divergence in Trimofphodon
in western Mexico. In addition we suspect that a detailed study of
Trimorphodon biscutatus, lambda, lyrophanes, paucimaculata and
vandenburghi will show that these nominal populations are all representative
of a single species.
Trimorphodon is a nocturnal species that is frequently found in
or about rocky areas. Two specimens from San Ignacio were found
about 3 meters above the ground in the rock foundation of a bridge.
Distribution in Sinaloa.—Throughout the state below about 1200
meters. See Fig. 86.