How many rows of teeth does a tuatara have on its upper jaw?

A tuatara has two rows of teeth on its upper jaw. One row is associated with the maxilla, while another row of palatal teeth grows from bones in the roof of the mouth.

The lower teeth fit between these two upper rows when the animal bites. This arrangement gives the tuatara an unusually effective shearing action: after closing its jaws, it can slide the lower jaw forward, helping it cut through tough prey such as insects and other invertebrates.

Tuatara teeth are acrodont, meaning they are fused to the jawbone rather than set in sockets. They are not replaced throughout life. As the teeth wear down, older animals increasingly rely on softer foods, and very old tuatara may eventually chew with worn, smooth jaw edges.

The tuatara is not a lizard, although it resembles one. It is the only living member of Rhynchocephalia, an ancient reptile lineage. Its Māori name means “peaks on the back,” referring to the prominent dorsal crest, especially in males.