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

120 UNIVERSITY OF KANSAS PUBLS., MUS. NAT. HIST,
and Smith and Taylor (1950b :73-76) allocated C. brachylopha,
C. breviwstris and C. parkeri to the synonymy of C. pectinata.
Specimens of C. acanthura reported from western Mexico were
designated as C. pectinata (Smith and Taylor, 1950b:74, footnote).
Smith and Taylor (1950b: 73, 75) characterized C. hemilopha as
posessing a single row of small scales between the fourth and fifth
rows of enlarged caudal spines, and having a range including
southern Baja California and central Sonora to northern Sinaloa.
They characterized C. pectinata as possessing three rows of small
scales between the fourth and fifth proximal rows of enlarged
caudal spines, and having a range from southern Sinaloa southward
to the Isthmus of Tehuantepec, Oaxaca. Other authors have followed
Smith and Taylor in distinguishing between C, hemilopha
and C. pectinata in Sinaloa (Smith and Van Gelder, 1955:145;
Fugler and Dixon, 1961:11). Bailey (1928:8-9) stated that the
median enlarged dorsal scales are interrupted at the sacrum in
hemilopha and complete to the end of the tail in C, pectinata.
In an effort to clarify the relationships between these two species
in Sinaloa, we examined more than 150 specimens of Ctenosaura
from western Mexico. All specimens of C. hemilopha examined
from throughout its range have the dorsals interrupted over the
sacrum. Of 99 specimens of pectinata examined, 46 per cent possessed
a complete row of enlarged dorsal scales, whereas 54 per
cent had enlarged dorsal scales interrupted over the sacrum.
This condition might suggest a clinal trend in dorsal scales from
interrupted series in the north to a complete series in the south.
However, there was no geographic trend in the dorsal scale row
character in C. pectinata from Sinaloa to Colima, both conditions
occurring throughout this region. In Sinaloa, 36 of 50 specimens
of C. pectinata examined for this character have the enlarged dorsal
scales interrupted over the sacrum. Individuals in a large series of
C similis from Costa Rica have a complete row of dorsal scales.
If similis were included in the above analysis, a clinical gradient is
indicated for this character from Sonora, Mexico, to Panama.
The number of small scale rows between the fourth and fifth
caudal whorls varies in the specimens examined. Damaged specimens
were not included in the following counts. Twenty-six of 54
specimens (48$) of C. hemilopha have a single row of small scales
preceding the fifth caudal whorl; 28 specimens (52$) have two
rows of scales preceding the fifth caudal whorl. In Sinaloa, 14
specimens (56%) of hemilopha have one row of small scales and