1) Class 2) Subclass anapsida 
(from the article `vertebrate`) ...or 4-chambered heart with incomplete ventricle separation; 12 pairs of cranial nerves; internal fertilization, direct development; oviparous and ... ...crocodiles, and birds); the captorhinomorphs, `stem reptiles` from which most other reptiles are thought to have evolved; eosuchians, early ....
The Anapsida are a subclass of reptiles in which there are no temporal vacuities.
[n] - oldest known reptiles: turtles
Anapsida The oldest known reptiles: turtles; extinct Permian forms.
subclass Anapsida noun oldest known reptiles: turtles; extinct Permian forms