The tuatara’s third eye

December 11, 2014 • 12:44 pm

by Greg Mayer

The tuatara has long been of interest to us here at WEIT, where we refer to it as Earth’s Only Extant Non-Squamate Lepidosaur*. We’ve been especially interested in the tuatara’s third, or parietal, eye, and our most recent post on it, which included a very nice color image of a longitudinal section of the eye, lamented the fact that we could not find any images of the eye from the outside, showing how the eye looks on the head of a tuatara. In that post I wondered whether my colleague Jon Losos, who had commiserated with us on the apparent absence of tuatara third eye photos, might not be able to help us out. Well, he’s come through– I give you the tuatara’s third eye:

The parietal eye of the tuatara, from Alison Cree's Tuatara (Canterbury University Press, Christchurch, NS, 2014).
The parietal eye of the tuatara, from Alison Cree’s Tuatara (Canterbury University Press, Christchurch, NZ, 2014).

The images (click to enlarge) are from Alison Cree’s Tuatara: Biology and Conservation of a Venerable Survivor (Canterbury University Press, Christchurch, 2014).  It does not (at least from the photos) look very different from the parietal eye of lizards, many of which also have parietal eyes, though not as well developed internally as in the tuatara. As a refresher from our earlier discussions here on WEIT, the ancestors of tuatara and lizards did not have a “normal”, functional third eye in the middle of their heads. Read the captions in the photos above for more details on the external appearance of the eye.

Jon included the images in his review of the book at Anole Annals (the published version of the review, sans photos from the book, will be in The Journal of the Royal Society of New Zealand). Some of the issues brought up in the book that Jon notes in his review are ones we’ve dealt with here at WEIT: the perennial confusion of tuatara with lizards (and even dinosaurs!)—Jon notes from the book someone who said tuatara were “ancestral to crocodiles and turtles”!; and the proper Maori plural of tuatara (it’s tuatara, as was explained to us by WEIT readers and Maori speakers Shuggy and Jax). The most interesting thing Jon notes about the book is that it rebuts the notion of the tuatara as a poorly adapted, barely-hanging-on, survivor, arguing, among other things, that the primitive diapsid skull structure of the tuatara is a reversal, not the retention of a primitive condition. This underscores a point made by the late Carl Gans in his essay “Is Sphenodon punctatus a maladapted relic?” (the answer is “No!”).

Jon summarized his review to me this way: “It’s a great book …everything tuatara!” And, it’s got tuatara eyes!

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Cree, A. 2014. Tuatara: Biology and Conservation of a Venerable Survivor. Canterbury University Press, Christchurch. Amazon

Gans, C. 1983. Is Sphenodon punctatus a maladpted relict? pp. 613-620 in A.G.J. Rhodin and K. Miyata, eds. Advances in Herpetology and Evolutionary Biology. Museum Of Comparative Zoology, Cambridge, Mass. BHL

17 thoughts on “The tuatara’s third eye

  1. The parietal eye sounds like its function is similar to that of the sensor on my landscape lights. Thanks to Shuggie and Jax not only for the Maori language lesson but also for having such badass names.

  2. I’m one of the lucky ones whose seen tuatara in real life in two of our wildlife parks that’re protected from introduced predators. It’s a real privilege to be able to watch them. I’ve got pics, but as they were taken under trees, the light isn’t very good.

      1. We are lucky in Wellington to have three good viewing sites:
        1. the predator-proof sanctuary Zealandia in Karori – well worth a visit anyway (Geologic podcaster George Hrab was rapt last week to see it and Weta Workshop on the same day). The tuatara are shy, but visitors are encouraged to keep notices of recent sightings up-to-date with felt-tip pens.
        2. Matiu (Somes Island) in the middle of Wellington harbour, a 20-minute ferry trip. Sightings not guaranteed, but guides tell you the best places to look, and again a fascinating place for other reasons.
        3. Behind glass in the Von Zedlitz building of Victoria University of Wellington, Kelburn Parade.
        Don’t expect them to do tricks. As a child I was tearfully convinced my father and brother were fooling me and the one we were watching was immobile because it was stuffed. (Cue Dead Parrot sketch in reverse.)

        1. Ha ha re: stuffed. I think that’s actually the good thing. I got to look at the tuatara behind glass for a long time! I saw them at Rainbow Springs when I was visiting family.

  3. “Anole Annals” might be the best name ever.

    Only improved, maybe, by referring to analysis and coming out annually.

  4. The photos were taken from specimens on Stephens Island which is interesting because it was there that the last Stephens Island wren existed. This was the only nocturnal flightless insectivorous passerine bird, now sadly extinct owing to predation by feral cats.
    Yes, cats!

    1. The standard pronunciation is the first. However, the second pronunciation is more nearly correct etymologically. The English word “anole” comes from West Indian French Creole. In Haiti, for example, the word is “zanolite”, or, rendered more phonetically, “zanoleet”. (The “z” is derived from an article preceding a noun, and commonly made part of the word itself in Haitian Creole, e.g. Creole “zwazo” from French “oiseau”. I’m not sure about the “t” sound at the end, but that’s how my colleague, who recorded the word from conversations with Haitians, said it.)

      GCM

      1. “CREE ohl,” or “cree OH lee?”

        😀

        Well, good, I’d always said uh-KNOLL, but a while ago ran into the other pronunciation and began to doubt myself.

        Thank you for the interesting etymology and mini-lesson in Creole linguistics.

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