systematics of snakes of the dipsas oreas complex - BioOne

128 Bulletin Museum of Comparative Zoology, Vol. 158, No. 3
temporalis. All of these are known from
Ecuador, but only D. oreas and D. gracilis
have been reported from Peru. The key
also includes three additional species
known or expected in the Chocó region of
Colombia: Dipsas sanctijohannis, D. viguieri,
and (possibly) D. nicholsi; the last
species, previously known only from central
Panama (Cadle and Myers, 2003), has
recently been recorded in eastern Panama
near the Colombian border (Myers et al.,
unpublished data). Characters of D. nicholsi
and D. andiana in the key are based
on diagnoses given in Cadle and Myers
(2003) and another female of D. nicholsi
reported by Myers et al. (ms.). The differential
characteristics of D. sanctijohannis
in the key are based on data from Peters
(1960a) and on data kindly provided by
Charles W. Myers from specimens he examined.
Characters of all other species are
based on discussions in this paper (D. elegans,
D. ellipsifera, D. gracilis, D. oreas)
or unpublished data (D. temporalis) in
conjunction with some data from Peters
(1960a).
Without additional study, I am unable to
adequately differentiate Dipsas viguieri
(eastern Panama and northern Chocó, Colombia)
and D. gracilis (western Ecuador
and extreme northern Peru). Geography
currently seems to be the only reliable
means of assigning names to specimens of
these species. The characters that Peters
(1960a) used to distinguish D. viguieri and
D. gracilis (e.g., preocular presence/absence,
number of postoculars) are known
to be highly variable intraspecifically within
Dipsas. Peters (1960a: 52) considered
the two perhaps only ‘‘subspecifically distinct’’
and otherwise noted (Peters, 1960a:
48) that ‘‘The characters separating [Dipsas
gracilis] and D. viguieri are comparatively
weak ones....’’Thus, specimens of
D. viguieri will key out to D. gracilis with
this key. The differential characters (if any)
of these two species and the disjunction
(or lack thereof) between their ranges in
western Colombia require further research.
Nonetheless, if these two taxa are
closely related or conspecific, then they
would add a third example within Dipsas
of a biogeographic connection between
northwestern (Chocoan) South America
and eastern Panama. The other examples
are D. andiana–D. nicholsi (Cadle and
Myers, 2003) and D. temporalis, which has
scattered records from northwestern Ecuador
into eastern Panama.
In addition to illustrations provided
herein, illustrations and discussions of
some of the relevant taxa are found in Peters
(1960a; D. gracilis, pl. Ib, c and D.
ellipsifera, pl. IVa), Kofron (1982; D. elegans,
D. ellipsifera, and D. oreas), and Cadle
and Myers (2003; D. andiana, D. nicholsi,
and D. oreas). The key is dichotomous
except for the last numbered section,
a triplet.
1. Dorsal bands very broad anteriorly and posteriorly,
covering 8 or more dorsal scale rows
in longitudinal dimension; bands continuous,
or nearly so, across the venter at least anteriorly.
Subcaudals 90, often 100 (up to
132). Tail 29% of total length. Either no
infralabials in contact behind the mental
scale, or one pair in contact ----------------------------- 2
– Dorsal bands narrower, covering 10 or fewer
dorsal scale rows in longitudinal dimension
(usually 7); anterior bands usually much
broader than posterior bands, and all bands
end on outer edges of ventrals or on lowermost
dorsal rows. Subcaudal counts variable,
but usually 100 (except male D. andiana,
up to 106). Tail 28% of total length.
At least one pair of infralabials in contact
behind the mental scale ----------------------------------- 3
2. No infralabials in contact behind the mental
scale. Anterior pair of chin shields very
small (in contact with mental), followed by
a pair of much larger chin shields. ----------
---------------------------------- Dipsas temporalis (Werner)
(eastern Panama, western [Chocoan] Colombia,
and western Ecuador; primarily in
low uplands in Panama, 800–1,000 m; apparently
also in the lowlands in Colombia
and Ecuador)
– One pair of infralabials in contact behind the
mental scale. Anterior pair of chin shields
about the same size as, or only slightly
smaller than, the second pair. -------------------
----------------------------------- Dipsas gracilis (Boulenger)
(lowlands [150–620 m] of western Ecuador
from just north of the equator to extreme
northwestern Peru [Tumbes and, less cer-