Oliver, S.C., Jamieson, B.G.M. and
Scheltinga, D.M.
1996c. The ultrastructure of spermatozoa of Squamata. II. Agamidae,
Varanidae, Colubridae, Elapidae, and Boidae (Reptilia). Herpetologica
52, 216-241.`
Spermatozoal synapomorphies for the Squamata
s. strict. are extension of the flagellar fibrous sheath into the
midpiece, the
paracrystalline nature of the subacrosomal cone, a single perforatorium
in
place of the two or three of Sphenodontida and Chelonia, loss of the
endonuclear canal, presence of sinuous mitochondria (though a columnar
form is
intuitively preferred), intermitochondrial dense bodies, an epinuclear
electron-lucent region, and, equivocally, arrangement of the dense
bodies as
periodic rings. Each of the taxa "Sauria," Scincomorpha, Scincidae,
and Iguania is not monophyletic. A suite of character states of the
sperm of
Varanus gouldii is known in
the Sphenomorphus and egernid (Tiliqua
scincoides)
groups of the Scincidae and in the teiid, Cnemidophorus sexlineatus,
although
some are also seen in the agamid Pogona
barbata. Cladistically, Pogona
forms
the sister-taxon of Varanus,
but only the presence of ovoid
perforatorial basal
plates, which are not entirely similar, appears to be a varanid-agamid
synapomorphy and is homoplasically present in Eugongylus group skinks.
Snakes
appear to be the sister-group of a Eugongylus group skinks + pygopod
clade.
Snake sperm have multilaminar sperm cell-membranes (an apomorphy shared
only
with the Pygopodidae) and are unique in the Squamata in the immense
elongation
of the midpiece; further, snake apomorphies are reduction of the
epinuclear
electron-lucent region and reduction or loss of the perforatorial base
plate,
and greater development of extracellular tubules than is known in any
other
squamate. Varanid-snake, iguanid-snake, and teiid-lacertid
relationships are
not cladistically upheld.