Recent advances in the field of squamate reptile chemoreception have b
een paralleled by the growth and preeminence of cladistics in the fiel
d of systematics, but for the most part, workers in the former have fa
iled to incorporate the conceptual and informational advances of the l
atter. In this paper, I attempt a preliminary rapprochement by combini
ng the methods of phylogenetic systematics and current hypotheses of s
quamate relationships with an overview of squamate chemosensory biolog
y. This purely phylogenetic approach leads to a number of falsifiable
generalizations about the evolution of chemoreception in squamates: 1)
Evolution of this system is conservative rather than plastic, reflect
ing to a large extent suprafamilial attributes rather than adaptation
to local conditions; 2) Anguimorphs are highly chemosensory and teiids
show convergence with this group; 3) Tongue-flicking, a bifurcated to
ngue tip, a vomeronasal (VNO) mushroom body, and a complete circular m
uscle system in the tongue are a correlated character complex associat
ed with the attainment, in squamates, of a direct VNO-oral connection
and the loss of a VNO-nasal connection; 4) There is little support for
a visual-chemosensory dichotomy within Squamata; 5) Gekkotans are all
ied with Autarchoglossa, both phylogenetically and in terms of chemose
nsory biology; 6) Iguania are highly variable in chemosensory developm
ent; iguanids represent the primitive iguanian condition, while agamid
s and chamaeleonids have secondarily reduced or lost their chemosensor
y abilities; 7) Apparent contradictions in chemosensory behavior among
iguanids probably represent intrafamilial divergence; 8) Ecological c
orrelates within Iguanidae and other taxa might be spurious, resulting
from historical factors unrelated to the adaptations in question; 9)
The mechanical demands of lingual food prehension have constrained che
mosensory evolution in Iguania; chemosensory evolution within Sclerogl
ossa was permitted by the liberation of the tongue from this ancestral
role.