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

152 UNIVERSITY OF KANSAS PUBLS., MUS. NAT. HIST.
Specimens from western Mexico demonstrate wide overlap in
characters of horridum and exasperatum. The supranasal contacts
the postrostral in two of nine specimen of horridum; four of eight
specimens of horridum have eight or more scales between superciliaries;
the second supralabial contacts the nasal or prenasal in
six of nine specimens of horridum. Although we have not seen an
animal with a color pattern obviously intermediate between the
two races in Sinaloa, Bogert and Martin del Campo (1956:65) suggested
clinal variation in this character as well. A detailed study
of Heloderma in northern Sinaloa probably will indicate that
exasperatum is representative of the northern terminus of Heloderma.
horridum and that clinal variation accounts for the distmctiveness
of this population, as visualized by Bogert and Martin del Campo
(1956:28). However, we continue to recognize two races in Sinaloa
until additional material from the foothills between the Rio Culiacan
and the Rio Fuerte becomes available.
Distribution m Sinaloa.—Known only from the area drained by
the Rio Fuerte. See Fig. 57.
Specimen examined.—13 km. NNE Vaca, 400 m. (* KU 80743).
Literature record.—San Bias, 100 m. {Bogert and Martin del Campo,
1956:32).
Heloderma horridum horridum (Wiegmann)
Trachyderma horridum Wiegmann, Isis von Olcen, 22:421, 1829 (type
locality, "Mexico"; type locality restricted to Cuemavaca, Morelos by
Bogert and Martin del Campo, Bull. Amer, Mus. Nat Hist., 109:21,
April 16, 1956).
Heloderma horridum Wiegmann, Isis von Oken, 22:628, 1829.
Heloderma horridum horridum: Bogert and Martin del Campo, Bull. Amer.
Mus. Nat Hist., 109:20, April 16,1956.
Remarks.—Three specimens of Heloderma h. horridum (KU
73770, 78905-06) have the following characteristics, respectively:
snout-vent lengths 246, 310, 268; tail lengths 192, 227, 189; tail/
snout-vent length ratios 0.78, 0.73, 0.72; ventrals from gular fold to
anus 62, 64, 62; subcaudals 84, 78, 78; scales across head between
posterior superciliaries 9, 7, 7; pairs of infralabials reaching chin
shields 2, 1, 1; supranasal contacts postnasal no, yes, no; preanal
scales not enlarged. Two specimens are essentially similar in pattern,
having a brown ground color with yellow scales appearing
just anterior to midbody; the yellow scales become more numerous
from anterior to posterior, and there are five pairs of yellow bands
on the tail. The yellow spots begin on the nape of the other lizard
(KU 78906).