Something to Chew On

Tuatara punctatus

Tuatara punctatus male by Phillip Capper

It’s tempting to call them lizards, but they’re not lizards. Tuatara are an entirely separate order from lizards and snakes, which are their closest living relatives.

These are some very interesting animals for many reasons, such as their longevity*, unusual sensory organs and skeletal features, and have most recently received attention for the way they chew.

Complex chewing behavior is normally only seen among animals with high metabolisms; not reptiles. Tuatara however have unusually low metabolisms even among reptiles, with their average body temperatures being between 41–52°F, as opposed to the average for reptiles of about 68°F, or our own bodies which average 98.6°F, and this makes their chewing very unusual.

In other reptiles, for example snakes, the teeth and jaws are used to help hold prey and pull it into the mouth to be essentially swallowed whole. Tuatara however have two rows of teeth in the upper jaw, and one row in the lower jaw which fits perfectly between the two upper rows. Once a their jaws close, the lower jaw also moves forward and even rotates slightly before the mouth opens again, cutting through food like a steak knife (or three).

Much of this information is not new to science, so although it may prove to some who still believed that there was a very strong link between complex chewing behavior and high metabolism that the link has been overstated, there are two other important things that this story is good for.

  • 1. To introduce more people to the amazing Tuatara and help to make sure this 200 million year old lineage extends far into the future.
  • 2. To highlight the work done at Hull University where researchers constructed the most detailed musculoskeletal 3D model of a skull that has ever been produced. This model has helped to examine the detailed inner workings of Tuatara jaws without harming any of these rare animals in the process. You can see the model and real, living Tuatara in the video below.

* In 2009 a 111 year old male successfully produced offspring, but we don’t know yet how long they can live or at what age they might not be able to reproduce anymore.