46 
Northcutt 
lamina 12 is the main optic layer and is 
always better developed than lamina 14. 
Laminae 8 and 10 are not nearly as well 
developed as in the previously described 
iguanid tectal pattern, and laminae 8 and 
10 are even difficult to recognize as distinctly 
separate laminae (Fig. 16). Lamina 7 con- 
sists of one major group of cells with little, 
if any, overlap with lamina 6. The peri- 
ventricular laminae are much more devel- 
oped, lamina 5 being twice the thickness of 
the comparable lamina in the iguanid tectal 
pattern. 
The organization of the tectum in Spheno- 
don is particularly interesting when com- 
pared to the iguanid and lacertid tectal pat- 
terns. Lamina 12 is the main optic fiber 
layer in Sphenodon, while lamina 14 is 
barely recognizable (Fig. 17). Lamina 10 
can be recognized as a poorly scattered layer 
of cell bodies, while the position of lamina 8 
is primarily distinguished by the presence of 
large myelinated axons and only a few cell 
bodies. Lamina 7 in Sphenodon is less devel- 
oped than lamina 7 in either lacertids or 
iguanids. The periventricular laminae of 
Sphenodon are very extensive, accounting 
for almost a third of the total thickness of 
the tectum. Lamina 5 is particularly well 
developed and consists of four to five dis- 
tinct subdivisions. Clearly, the laminar ar- 
rangement in Sphenodon is more like the 
lacertid than the iguanid tectal pattern. 
Consideration of the entire range of tectal 
variation in Sphenodon and lizards reveals 
that there are no de novo laminae restricted 
to a single taxon, but that sufficient laminar 
variation occurs to characterize taxa at the 
family level. 
Gekkonids and pygopodids both possess 
three to five subdivisions in lamina 5 of the 
periventricular tectal zone. Gekkonids can 
be recognized from pygopodids and most 
other lizards by a partial fusion of laminae 
7 and 8. Xantusia possesses a tectal lamina- 
tion that appears intermediate between that 
of gekkonids and that of lacertids. 
Both lacertids and scincids possess tecta 
whose organization is comparable to Spheno- 
don and many turtles, particularly Chelydra 
and Kinosternon. The tectum of skinks dif- 
fers from that of lacertids in that it does not 
exhibit a distinct lamina 4, free of cell bodies, 
as does the lacertid tectum, and zone 5 in 
skinks does not exhibit distinct subdivisions. 
The tecta of Feylinia and Typhlosaurus 
differ from those of most skinks in the reduc- 
tion of the superficial tectal zone, but these 
taxa otherwise possess tecta that are identical 
to those of other skinks. The tecta of Anely- 
tropsis and Dibamus also possess reduced 
superficial zones related to reduction in visual 
projections, but they differ from skinks in 
that both of these genera develop a paratorus 
and do not possess a recognizable lamina 4 
(Senn and Northcutt, 1973). 
Xenosaurus, Anguis, and Anniella possess 
very similar tecta, but Xenosaurus can be 
separated from the other two genera on the 
basis of the development of lamina 5. Lamina 
5 in Xenosaurus consists of subdivisions one 
to two cells deep, while Anguis and An- 
niella have subdivisions two to four cells 
deep. 
Both Cordylus and Gerrhosaurus reduce 
lamina 2 and increase the number of sub- 
divisions recognized in lamina 5. 
Heloderma and Lanthanotus possess peri- 
ventricular laminae similar to the lacertids, 
but both genera show reductions of the 
superficial tectal zone. There is a reduction 
in lamina 13 so that distinct and separate 
laminae 12 and 14 cannot be recognized. 
Teiids and varanids possess almost iden- 
tical tecta. Both taxa possess hypertrophied 
laminae 14 and reduced periventricular tectal 
laminae. Teiids can be recognized from 
varanids by increased mediolateral thickness 
of lamina 14 and by a better developed 
lamina 5 than varanids. Both the macro- and 
microteiids exhibit identical tectal develop- 
ment. 
Agamids, chamaeleonids, and iguanids 
have tecta that are so similar it is almost 
impossible to distinguish among them. As a 
group, these taxa can be separated from 
the teiids and varanids by clearer subdi- 
visions of lamina 7 and by better developed 
periventricular zones. The superficial tectal 
zones of teiids and varanids are identical to 
