Biology Reference
In-Depth Information
1
An Overview of the Artificial
Assemblage, the Colubridae:
A Brief Summary of Taxonomic
Considerations
The taxonomy of this former assemblage is in dynamic transition and subject to
frequent and often conflicting recommended rearrangement. This very large artifi-
cial grouping often functioned as a sort of “disposal depot” (colloquially known as
a “taxonomic garbage can” or “rag bag”) for taxa of unestablished affinities. This
resulted in the incorrect assignment of many diverse and phylogenetically unrelated
ophidian species. For over 30 years, numerous taxonomists have devoted increasing
attention to resolving this complex issue by using methods involving morphologi-
cal (based on osteology, dentition, hemipenal morphology, lepidosis/meristics, etc.)
or molecular (analysis of nuclear or mitochondrial DNA sequences—sometimes
inferred from ribosomal RNA sequences—allozyme electrophoresis, immunodif-
fusion, etc.) methods or, less commonly, combined morphological and molecular
systematics (Cadle, 1988; Dessauer et al., 1987; Dowling et al., 1983, 1996; Heise
et al., 1995; Jenner and Dowling, 1985; Kraus and Brown, 1998; Lawson et al., 2005;
Pinou et al., 2004; Vidal et al., 2000, 2007, 2010; Zaher, 1999; Zaher et al., 2009).
Discussion of the current status of these ongoing reassignments is far too volumi-
nous to detail here. However, some recommended changes are summarized in
Table
1.1
. Analyses of previous taxonomic assignments have increasingly been subject
to more of a “splitting” (e.g., division of a given species, genus, subfamily, or family
into separate entities) approach, rather than “lumping” these together. For instance, the
crayfish-eating snakes (
Regina
spp.) of the tribe Thamnophiini are polyphyletic, and the
Thamnophiini itself has at least three major clades (Alfaro and Arnold, 2001). Ongoing
phylogenetic investigations will probably modify numerous subfamilies, genera, and
re-define existing lineages (Hedges et al., 2009; Pyron et al., 2011). It should be noted
that several medically important species have been recently reassigned. For example,
Vidal et al. (2007) and Zaher et al. (2009) recommended raising the previous subfamily,
Natricinae, to a full family, Natricidae (see
Table 1.1
). This family contains
Rhabdophis
tigrinus
and
R. subminiatus
, two species that have inflicted fatal or life-threatening bites
(Section 4.2). Such reassignments reinforce the call for the use of precise and current
taxonomy in clinical toxinology (Wüster et al., 1998). Some species can be reassigned;
this can lead to controversy and confusion in the literature. For example, historically, the
front-fanged mole vipers, burrowing asps, or stiletto snakes (
Atractaspis
spp., approxi-
mately 18 species;
Plate 1.1A
), were first considered viperids or elapids, then reassigned
to the colubrid subfamily, Aparallactinae (the centipede-eating snakes), then placed in
