The Amazing Walking Fossil
Tuataras are pretty amazing animals for a number of reasons. They live on New Zealand, and were originally believed to be lizards. However, in 1867, dr. Albert Gunther (curator at the British Museum in London) was examining a bottled tuatara specimen and exclaimed "This is not a lizard!" If you had witnessed this, you'd probably believe the man was an absolute kook. However, he noticed a few subtle things on the tuatara that didn't really look like anything known on lizards:
- The arrangement of their teeth is unique. A single row of teeth in the lower jaw fits between two rows of teeth in the upper jaw. No lizard has a tooth structure like that.
- The specimen he was examining was a male -- but it did not have a penis!
- There was a very strange-looking scale on top of its head, which didn't look like anything a lizard would have. Beneath this translucent scale was a simple third eye, complete with retina.
- It had no ear openings. All lizards known by that time did (a single lizard species without ears, the Earless Monitor, has since been discovered)
Strange indeed. The scientist realized that this strange creature (which he was informed was found in New Zealand shortly before) bore striking similarities to the prehistoric reptile order Rhynchocephalia, which herpetologists of the time agreed had been extinct for 60 million years, and lived at the same time as the dinosaurs.
Indeed, the tuatara is an ancient creature, possibly the oldest known vertebrate. Judging from fossil evidence, modern tuataras are virtually identical to those that lived 225 million years ago. It is not uncommon for individual tuataras to have life spans of just over a century, and they grow to be around 50-60 centimeters long when fully grown.
A Third Eye
Perhaps the most well-known tuatara trait is the third eye. First of all, lizards and snakes have tiny, vestigial remnants of such eyes too (on many lizards, you can see a tiny, strange-looking dark spot on a scale on top of the animals' heads), but in the tuatara it is much more developed. Or, as it is, much less developed-away. While the "eye" has a retina and a simple lens, it does not appear to have well-developed vision at all, possibly only being able to distinguish between light and dark. It is part of a gland which serves a vital role in the growth of the tuatara, and soaks up ultraviolet radiation from the sunlight from which the young tuatara gets vitamin D -- it needs lots of this to grow. This is perhaps the explanation why the eye is eventually covered with translucent scales, its function is more important while the animal is young. Snakes and lizards can absorb vitamin D through their scaly skin, unlike the tuatara.
Tuatara males share an important trait with many male human computer programmers: Females aren't usually terribly interested in them. Unlike lizards (female and male lizards usually have mating on their minds at approximately the same time of year), tuatara females are ready to mate approximately once every four years, whereas the male is always ready to mate. Wait a minute! The male doesn't have a penis, how can they mate at all? The way all prehistoric animals did it, the male passes his sperm straight from his cloaca to hers. Their mating rituals are quite peaceful as far as reptiles go, the males will sit outside their burrows and wait for passing females; if one comes by he will crawl over and circle around her. If she's interested, she'll present herself and they'll mate. If she isn't, the male will simply go back to his burrow and wait for another one to come by. (why do silly humans have to make everything so damn complicated?!)
The female will lay around 6-8 eggs, about nine months later (most lizards take much shorter time to lay eggs). The eggs will hatch around 16 months later -- also, this is a very long time compared to most other reptiles.
Tuataras have a number of other strange, unique and interesting traits:
- They can hold their breath for nearly an hour. Beat THAT, Guybrush Threepwood!
- Tuataras have the slowest growth rate of any known reptile. They reach full adult size when they are around 30-35 years old.
- Their teeth are specially adapted to ripping the heads off of things. When tuataras hunt, they usually seek out lizards or small seabirds, and tear their heads off before eating them.
- Adult tuataras are nocturnal and prefer to go out when there's somewhat cold. They spend the day sleeping in their burrows or lazily dozing in the sun -- like all reptiles they are exothermic, and need warmth to be able to digest their food.
- Young tuataras are diurnal, because they will be eaten by adult tuataras if they go out to hunt at night.
The most funky thing about them, however, is that this species is hundreds of millions of years old and almost unchanged. The reason for this is that they live in New Zealand, and many of the predators that killed off the species in the rest of the world never arrived to this isolated region. Unfortunately, when humans got to New Zealand they brought all sorts of foreign animals with them, most notably the main cause of dwindling tuatara numbers, the rats (who prey on young tuatara, eggs, and sleeping adults). They are now an endangered species, a few thousand specimens remain on the planet, confined to small outlying islands around New Zealand. Their slow breeding cycle makes it very difficult, perhaps impossible, for the species to recover their past numbers.