Polyphyodontia

Polyphyodontia refers to a condition in dentition where teeth are continuously replaced throughout an animal's life. Unlike diphyodonts, which have two sets of teeth (baby and adult), polyphyodonts can go through many successive generations of teeth. This is a common characteristic among many vertebrate groups, including fish, amphibians, reptiles, and most mammals, though the rate of replacement varies significantly. In some species, like sharks, teeth are constantly shed and replaced in a conveyor-belt fashion, ensuring a sharp and functional set is always available for predation. Other animals may replace teeth less frequently but still experience multiple sets over their lifetime. This continuous replacement is often an adaptation to a diet that wears down teeth quickly, such as abrasive plant matter or hard prey. The structure of the jaws and the mechanisms for tooth replacement are highly specialized in polyphyodont species. The arrangement and replacement pattern can differ, with some having a mesial drift where new teeth erupt behind older ones, pushing them forward and eventually off. The term itself derives from Greek words meaning "many" and "tooth," directly reflecting the condition of having numerous tooth generations.