Campus Life

Sphenodon punctatus: The Three-Eyed Not-A-Lizard | Houston’s Zoo No. 07

A few weeks ago, a reader requested a feature on lizards. Of course, that was far too general for me, so I sat down to decide on a specific type of lizard. The problem is, there are SO many kinds of lizards in the world. I changed my mind dozens of times over the week. Gila Monster. Marine Iguana. Basilisk. Komodo Dragon. Each one deserves its own article. Finally, it came to Friday night, and the only thing I knew for sure was that I WASN’T going to feature a lizard this week.

So I went with the first non-lizard I thought of: New Zealand’s unique little reptile, the tuatara.

To the untrained eye, this looks like some kind of joke. Obviously, the animal shown in these pictures is a lizard, right? Au contraire, mon lecteur. The tuatara is no more a lizard than it is a flamingo. As a matter of fact, lizards are more closely related to snakes than they are to tuataras.

The tuatara belongs to the order rhyncocephalia. It is the only species in the only genus in the only family in that order. There is, quite literally, nothing like it in existence. Their closest relatives died out with the dinosaurs. They are what many refer to as “living fossils.” Reptilian representatives of a bygone (mesozoic) era.

Aside from looking like the offspring of a dwarf crocodile and Kermit the Frog, the tuatara is relatively unremarkable in appearance. They are the largest reptiles in New Zealand, growing up to about 20 inches in length, and weighing a little over three pounds. They range in color from brown to green to orange, and–in males–have a line of spines down their necks and backs. These spines can be fanned out in a courtship display, or to appear more impressive to rival males.

The most impressive thing about tuataras, though, is not their spines. It’s their eyes. Or rather, one of their eyes. They have two ordinary eyes, right where you expect to see them, but they also have a third eye. On the top of their head. This third eye, called a parietal eye, can not truly see, but it can detect the difference between light and dark. It is only visible in hatchlings. A few months after hatching, the tuatara grows a patch of skin over this primitive sensory organ. However, the eye retains its functionality throughout the tuatara’s 60-100 year lifespan.

It’s exact function is still a matter of some debate, but it is believed that the parietal eye is involved in circadian rhythm and in producing certain hormones. Tuataras are, admittedly, not alone in having a parietal eye. Some lizards, amphibians, and fish possess similar organs, but the tuatara’s is particularly well developed.

Tuataras are a special animal. They have been since the age of the (large, extinct, flightless) dinosaurs. They have a feature few animals can claim, and are only found in one place on Earth. They are not only the last of their kind, they are the last of their order. Truly, if any creature can be called an oddity, it’s this modest reptile of which no-one’s ever heard.


That’s all from me. If you have any questions, or would like to request an animal to be featured, comment down below and It’ll be my pleasure to help you out.

See you next weekend, and until then I am…

As I ever am.

Categories: Campus Life, Feature

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