Thecodont dentition is a morphological arrangement in which the base of the tooth is completely enclosed in a deep socket of bone, as seen in crocodilians, dinosaurs and mammals, and opposed to Acrodont and Pleurodont dentition seen in Squamate reptiles. This morphology was once used as a basis for the now-defunct taxonomic group Thecodontia.
References
Thecodont dentition Wikipedia(Text) CC BY-SA