In the true poisonous snakes the maxillary dentition has undergone a special modification.
The dentition is i, c 1, p 4, m L total 42.
On the other hand, there are those who believe that the functional dentition (other than the replacing premolar and the molars) correspond to the milk-dentition of placentals, and that the rudimentary tooth-germs represent a "prelacteal" dentition.
The tail is long and in some cases prehensile; the first hind-toe may be either large, small or absent; the dentition usually includes three pairs of upper and one of lower incisors, and six or seven pairs of cheekteeth in each jaw; the stomach is either simple or sadculated, without a cardiac gland; and there are four teats.
The remaining members of the family may be included in the sub family Phalangerinae, characterized by the normal nature of the dentition (which shows redimentary lower canines) and tongue.