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

AMPHIBIANS AND REPTILES OF SINALOA, MEXICO 197
temporals respectively (in order as listed in specimens examined).
Each specimen has 8-8 supralabials, 9-9 infralabials, 2-2 preoculars,
2-2 postoculars, supralabials four and five entering the eye, and
the posterior pair of chin shields separated medially by a series of
small scales.
Smith (1943a:467) reported that the anterior nasal is separated
from the second supralabial in all (10) of the specimens (from
Guanajuato, Michoacan, Puebla, and Veracruz) that he examined.
Davis and Smith (1953:137) found the same condition in three
snakes from Morelos. The anterior nasal is in contact with the
second supralabial on every specimen from Sinaloa. The contact
of the anterior nasal and the second supralabial is reported to be
characteristic of S. grahamiae by Smith (1939b: 233), but is considered
to be of little, if any, taxonomic importance by Charles M.
Bogert (personal communication).
In the specimens from Sinaloa, the dorsolateral dark stripes
terminate on the nape just posterior to the parietal and temporal
regions. This characteristic distinguishes S. bairdi from S. lineata,
in which the dorsolateral dark stripes diverge on the neck and
pass through the temporal region to the eye. The Sinaloan specimens
of bairdi also have a dark lateral stripe on the third scale
row. The right maxilla of one specimen (KU 78918) has nine teeth
anterior to the diastema that separates them from larger teeth at
the posterior end of the jaw. In contrast, S. grahamiae lacks a
dark lateral stripe on the third scale row and usually has ten maxillary
teeth anterior to the fangs (Smith and Taylor, 1945:122).
However, it is of interest to note that the anterior nasal and the
second supralabial are separated in the southern part of the range
of bairdi (away from the range of grahamiae) and the nasal and
supralabial are in contact in the northern part of the range (close
to the range of grahamiae).
Bogert and Oliver (1945:403) suggested that S. bairdi and S.
lineata might intergrade in Hidalgo and Distrito Federal. Davis
and Dixon (1957a:21-22) reported a specimen from Michoacan
that was intermediate between bairdi and lineata and suggested
that they are probably subspecies of a single species. However,
Davis and Dixon regarded them as distinct species pending the
availability of more material. Duellman (1961:108) found only
one specimen that resembled lineata among 89 specimens from
Michoacan. Our specimens are typical of bairdi in most characters
but the overlap in some characters previously discussed suggests
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