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2006; Mitchell et al., 2010). However, due to the limited information about the bio-
logical function(s) of some of these dental modifications and oral secretion properties
in extant as well as in extinct species with very limited fossil remains, these interest-
ing data and related hypotheses should be very cautiously considered and subjected to
careful scrutiny in order to verify the proposed functions/roles (see later).
2.4 Duvernoy's Glands and Venom Glands: A Question of
Semantics?
In emphasizing phylogenetic considerations, some authors have suggested abandoning
terms (opisthoglyphous, rear-fanged, etc.) accentuating the enlarged maxillary
teeth present in some of these colubroid taxa (Vidal et al., 2000). Others have pro-
posed rejection of specific recognition of Duvernoy's glands, preferring to group these
with venom glands as defined for venomous front-fanged species such as elapids and
viperids (Fry et al., 2003, 2008). Kardong (1996), Weinstein and Kardong (1994),
and Weinstein et al. (2010) have conversely suggested that Duvernoy's glands are dis-
tinctive structures associated with various types of delivery apparatus. These authors
emphasized the aforementioned functional morphological differences between the
Duvernoy's gland low-pressure systems in comparison with that of the high-pressure
“true” venom glands (
Figure 2.1
). Delivery of venom or secretion volumes sufficient to
cause human morbidity or mortality are certainly influenced by the nature of the deliv-
ery system as outlined above. It is noteworthy that non-front-fanged colubroid taxa
widely recognized as venomous in a clinical and biological sense (e.g.,
D. typus
,
T.
kirtlandii
, and several others; see later) exhibit notably serous Duvernoy's glands with
some limited muscle attachment, some venom storage capacity, a highly toxic secre-
tion (venom), and enlarged, often grooved, posterior maxillary teeth (see Section 4.3).
Therefore, the distinctive morphology of the oral glands and related delivery apparatus
of these diverse snakes clearly influence their potential medical importance.
