26 
Northcutt 
Figure 8. Transverse sections through rostral (A) to caudal (C) levels of the right telencephalic hemisphere 
of the teiid Tupinambis nigropunctatus, stained to demonstrate neuron cell bodies. Bar scale represents 
2 mm.aot, accessory olfactory tract; cd, (Cl—3), dorsal cortex and its subdivisions; cl, lateral cortex; cm, 
(Cl-2) , medial cortex and its dorsal (Cl) and ventral (C2) subdivisions; dvr, dorsal ventricular ridge; 
na, nucleus accumbens; nat, nucleus of the accessory olfactory tract; ndb, nucleus of the diagonal band of 
Broca; not, nucleus of the lateral olfactory tract; ns, nucleus sphericus; st, striatum. 
can be related to higher categories as pres- 
ently defined on the basis of other non- 
neurological features. 
The first type of ridge, divided into super- 
ficial cellular plate and core, is probably 
closer to the ancestral state than is the ex- 
panded, complex ridge seen in iguanids and 
other taxa of the second group. Ancestral 
characters are usually recognized as charac- 
ters, or character states, that are scattered 
irregularly among a wide range of related 
taxa, and, in many cases, are found outside 
of the taxonomic category being examined 
(Mayr, 1969; Lynch, 1973). The rationale 
is that the more widely a character is dis- 
tributed, the more distant the relationship 
indicated and the more remote the common 
ancestry (Hennig, 1950). 
The DVR in most cryptodire turtles is also 
organized into a superficial cellular plate and 
central core (Northcutt, 1970). 
Furthermore, an examination of the DVR 
of Sphenodon, the sole living rhynchoceph- 
alian and, thus, the reptilian taxon most 
closely related to squamates, reveals a state 
of development that is even more simple 
than the dorsal ventricular ridge of squa- 
mates or turtles (Fig. 9). The ridge in 
Sphenodon consists of a plate of cells that is 
continuous with the ventral border of the 
lateral cortex. No giant cells can be identified 
in this cellular plate as were seen in gek- 
konids. The plate cells of the ridge possess 
multiple apical dendrites which extend ven- 
trally into a neuropil that contains only a 
few neurons. These migrated neurons may be 
homologous to the core neurons in the ridge 
of lizards. SDH preparations of the ridge in 
