1	Rudimentary eyes; ventral and dorsal scales of equal size	Typhlopidae (Amerotyphlops brongersmianus)
–	Developed eyes; ventral scales larger than dorsals	2
2	Presence of loreal pit; solenoglyph dentition; keeled scales	Viperidae
–	Absence of loreal pit	3
3	Robust body; small undifferentiated cephalic scales; more than 30 dorsal scales	Boidae
–	Distinctive cephalic scales	4
4	Proteroglyph dentition	Elapidae
–	Aglyph or opisthoglyph dentition	Colubridae and Dipsadidae