摘要："Different modes of tooth implantation in squamates are reviewed and defined. Three basic types of tooth implantation are recognized in reptiles: acrodonty, thecodonty, and pleurodonty. Only acrodonty and pleurodonty are present in squamates. Variations of the pleurodont con-dition include full pleurodonty, labial pleurodonty, and subpleurodonty. Tooth implantation and replacement in mosasaur lizards and snakes are reviewed in order to evaluate previously proposed character definitions and hypotheses of primary homologies for three distinct characters associated with tooth replacement-the presence or absence of resorption pits, a recumbent or upright position of the replacement teeth, and the mode of tooth attachment to the bone. The first character is shown to be uninformative in respect to the controversy surrounding Mosasauroidea-snake affinities. Mosasaurs show replacement teeth in a normal upright position, and the occasional presence of recumbent teeth is the result of postmortem displacement. Finally, the mode of tooth attachment in snakes and mosasaurs is fundamentally different. The highly modified condition of tooth implantation described for the alethinophidian snakes is suggested to represent an additional synapomorphy of this taxon at the exclusion of the scolecophidians, which retain the plesiomorphic, fully pleurodont, lizard condition. The lower Middle Cretaceous fossil snake Pachyrhachis shows the alethinophidian type of tooth implantation"--P. [1].
