1. (invertebrate) Applied to a hinge dentition occurring in the Bivalvia, where teeth of differing sizes occur in the hinge plate. The teeth are differentiated into cardinal teeth, which occur beneath the umbo, and lateral teeth, which occur posteriorly and anteriorly to the umbo.
2. (vertebrate) Possessing teeth that are differentiated into several forms, e.g. incisors, canines, premolars, and molars (as in mammals). This contrasts with the homodont condition, in which the teeth are all of the same form.