systematics of snakes of the dipsas oreas complex - BioOne

Dipsas oreas Complex in Ecuador and Peru • Cadle 127
and how the names should apply to Ecuadorian
and Peruvian specimens.
Moreover, Peters (1960a) had little material
of each species, particularly from
near the type localities. He referred only
three specimens from extreme southern
Ecuador and northern Peru to D. latifasciata.
More problematic was his referral of
only one specimen from Venezuela to D.
latifrontalis but, in addition, 44 others
from eastern Ecuador. Thus, the distribution
of ‘‘Dipsas latifrontalis,’’ as Peters
(1960a: 99) conceived it, left a broad gap
across eastern Colombia, from which no
specimens referred to either of these species
were reported. Peters himself seems
to take great pains to justify his applications
of these names to samples available
to him based only on the type descriptions.
Similarly, he justified his referral of the
names Leptognathus palmeri Boulenger
(1912) (type locality, ‘‘El Topo, Río Pastaza,
Ecuador’’) and L. praeornata Werner
(1909) (type locality, ‘‘Venezuela’’) to the
synonymy of Dipsas latifrontalis by extended
discussion of relatively few characters
in the original descriptions (Peters,
1960a: 103, 109–110). The brevity of the
original descriptions of all these taxa and
the poor comprehension of intraspecific
variability within Dipsas at the time of
their descriptions mean that reference to
the types is needed to resolve the systematics
of these snakes.
These peculiarities and my interpretations
of some material that both Peters
and I examined lead me to question the
proper name of specimens from eastern
Ecuador and Peru. MCZ 17404, a specimen
that Peters (1960a) assigned to D. latifasciata,
has the pattern by which he
characterized D. latifrontalis (all bands fail
to meet midventrally). In fact, Peters
(1960a: 103) stated that this specimen was
‘‘intermediate in some characters between
what might be called typical latifrontalis
and latifasciata. . . .’’ In three specimens
that Peters assigned to D. latifrontalis
from the same general area of Ecuador
(‘‘Llanganates Area’’ [probably southwestern
Napo Province]), two (FMNH 23530–
31) show the pattern characteristic ascribed
to D. latifrontalis, whereas FMNH
23532, although it has a predominantly
black venter, seems to have bands meeting
midventrally, the pattern that Peters ascribed
to D. latifasciata. Peters (1960a:
103) suggested the possibility that additional
collections might ‘‘demonstrate that
the relationship between [latifrontalis and
latifasciata] is at best on the subspecific
level.’’
Interpretive problems such as these suggest
that a new look at snakes with the
requisite characteristics from Venezuela,
Ecuador, and Peru is warranted. As with
many similar problems concerning species
identities in Dipsas, adequate resolution
will require renewed study of the types
and other geographically proximate specimens.
Consequently, Peters’ assignment of
specimens from eastern Ecuador to D. latifrontalis
is unconvincing, as is his suggestion
of a possible subspecific relationship
between D. latifrontalis and D. latifasciatus.
The specimens here referred to
D. latifasciata (see Specimens Examined
and Locality Records) are done so provisionally,
pending further study of the Ecuadorian,
Peruvian, and Venezuelan material
(including types) referred to D. latifasciata
and D. latifrontalis. Full resolution
of the systematics of this group should
also review the validity and proper synonymy
of the names Leptognathus palmeri
Boulenger (1912) and L. praeornata Werner
(1909), which Peters considered synonyms
of D. latifrontalis on the basis solely
of the type descriptions.
KEY TO SPECIES OF DIPSAS IN
WESTERN SOUTH AMERICA
I provide the following key to assist in
identifying species and individual specimens
of Dipsas in western South America.
Six species of Dipsas are known from the
western slopes of the Cordillera Occidental
and adjacent Pacific lowlands of Ecuador
and Peru: D. andiana, D. elegans, D.
ellipsifera, D. gracilis, D. oreas, and D.