systematics of snakes of the dipsas oreas complex - BioOne

86 Bulletin Museum of Comparative Zoology, Vol. 158, No. 3
well-developed papillate calyces. However,
the proximal papillae, especially those adjacent
to the fork of the sulcus spermaticus
and those fringing the overhang, have mineralized
tips. A very large (8 mm long)
nude pocket extends from the base of the
organ to the battery of spines; its distal end
is nestled within the proximal spines of the
battery. The pocket is on the dorsal surface
of the inverted organ (the lateral surface
of the everted organ relative to the sulcus
spermaticus). The pocket has a large lobe
on its absulcate edge and a smaller lobe
on its sulcate edge; these lobes also bear
minute scattered spines. The asulcate side
of the organ (medial side of the inverted
organ) bears 3 enlarged spines in a transverse
row, which are separated by a gap
(ornamented with minute spines) from the
battery of spines on the midsection.
The hemipenis of Dipsas ellipsifera is
similar in many details to hemipenes of
other snakes of the tribe Dipsadini that
have been described (review in Cadle and
Myers, 2003: 14–15). Features common to
hemipenes of the Dipsadini include welldeveloped
papillate calyces on the capitulum,
an encircling battery of enlarged
spines on the midsection, a relatively unornamented
base, and a very large nude
pocket proximally on either the asulcate or
lateral surface of the organ. The nude
pocket in D. ellipsifera is exceptionally
long, 44% of the length of the organ. In
other species examined by Cadle and Myers
(2003: 15) the pocket was approximately
33% of the length of the organ.
However, observations in Cadle and Myers
(2003) were based on everted organs and
it is not possible to know the relative proportions
of the nude pocket in the everted
hemipenis of D. ellipsifera because hemipenial
tissue expands differentially upon
eversion (see Myers and Cadle, 2003). The
proximally divided retractor muscle in D.
ellipsifera suggests that its everted hemipenis
may be somewhat more bilobed than
everted hemipenes of either D. elegans or
D. oreas described later herein. The degree
of bilobation apparently varies among
species of Dipsas (Cadle and Myers, 2003:
14–15).
Distribution and Natural History
Dipsas ellipsifera is known only from
the valley of the Río Mira in extreme
northwestern Ecuador (Fig. 8). All reported
specimens are from Imbabura Province;
the Río Mira divides Imbabura from
Carchi Province, and the species may also
occur in the latter province. Elevations for
the two localities for which specimens
were examined in this study are 2,000 and
2,211 m, but Orcés and Almendáriz (1987)
reported an elevational range of 572–2,600
m for this species (see Specimens Examined
and Locality Records). Several specimens
collected by Philip Hershkovitz
(UMMZ 83697–700) were obtained in
June and August, but most specimens are
not accompanied by specific collection
dates.
The type locality of Dipsas ellipsifera,
Ibarra, lies at 2,211 m elevation in a dry
rain shadow valley of the western Andes.
Rosenberg (quoted in Hartert, 1898) described
the vicinity of Ibarra at the time
the syntypes were collected as ‘‘. . . open,
and for the most part cultivated,’’ seemingly
quite different from a nearby locality
at a lower elevation to the west, Paramba
(Hacienda Paramba; Paynter, 1993),
which Rosenberg described as ‘‘densely
forested.’’ Orcés and Almendáriz (1987:
138) stated the following concerning localities
for D. ellipsifera: ‘‘. . . [the localities]
are found in the subtropical and temperate
zones. The region in question is for
the most part semiarid with shrubby vegetation;
in a few cases epiphytic and parasitic
plants are present. The temperature
varies from 18 to 22 C and the precipitation
from 500 to 1,000 mm.’’ Lita, the
most western locality and the lowest elevation
(572 m) from which D. ellipsifera
has been recorded (Orcés and Almendáriz,
1987), lies in the region of very humid
lowland rain forest characteristic of northwestern
Ecuador.
Because Peters (1960a) confused some