What Do Kangaroos, Elephants and Manatees Have in Common?
By Danielle Cookish
Teeth!
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The majority of toothed fish and several reptiles including crocodiles are called polyphyodonts. This is a term used to describe an animal whose teeth are continuously replaced during their lifetime. Kangaroos, elephants and manatees are all polyphyodonts, the unique mammalian exceptions.
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We humans have several different types of teeth, molars, incisors, premolars (bicuspid), canines (cuspid). Basically, we’ve got a lot going on in our mouths and we only get two sets. In contrast, manatees have hind molars and nothing more.
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Due to their diet of abrasive vegetation often mixed with sand, the manatee has developed a dental adaptation called “hind molar progression”, also referred to as “marching molars”. Eventually, these molars will wear down and fall out.
But what makes polyphyodonts so unique is the conveyor-belt-like action in which their teeth regrow. New molars are developed in the back of the jaw as old, worn down molars fall out in the front, creating a continuous forward-growth motion.
How cool is that?
