First evidence of hemiclitores in snakes

Female genitalia are conspicuously overlooked in comparison to their male
counterparts, limiting our understanding of sexual reproduction across
vertebrate lineages. This study is the first complete description of the
clitoris (hemiclitores) in female snakes. We describe morphological
variation in size and shape (n = 9 species, 4 families) that is
potentially comparable to the male intromittent organs in squamate
reptiles (hemipenes). Dissection, DiceCT and histology revealed that,
unlike lizard hemiclitores, the snake hemiclitores are non-eversible
structures. The two individual hemiclitores are
separated medially by connective tissue, forming a triangular structure
that extends posteriorly. Histology of the hemiclitores in Australian
death adder (Acanthophis antarcticus) showed erectile tissue and
strands/bundles of nerves, but no spines (as is found in male hemipenes).
These histological features suggest the snake hemiclitores have functional
significance in mating and definitively show that the hemiclitores are not
underdeveloped hemipenes or scent glands, which have been erroneously
indicated in other studies. Our discovery supports that hemiclitores have
been retained across squamates and provides preliminary evidence of
differences in this structure among snake species, which can be used to
further understand systematics, reproductive evolution and ecology across
squamate reptiles.