by Greg Mayer
Tuataras are in the news today, although there really isn’t that much new about them. In fact, as Natalie Angier points out in the New York Times, they are transparently Triassic in aspect, as the following picture, of a tuatara named Henry, will attest.
Angier provides a review of various interesting aspects of tuatara biology– they live a long time, reproduce slowly, eat giant orthopterans, are nearly extinct, etc. What’s most interesting about them is that they are the sole living members of one of the four major groups of extant reptiles, the Sphenodontida (an order in the Linnaean hierarchy of ranks, the other reptile orders being turtles, crocodiles, and snakes+lizards); and they are found only in New Zealand, where they are restricted to a few offshore islands. (They have recently been transplanted back to the mainland of New Zealand, whence they were extirpated centuries ago by introduced rats.)
Though they look much like lizards (iguanas or agamids in particular), and were thought to be lizards when first discovered, they are in fact not lizards, as anatomical examination reveals. They have a primitive type of skull, termed fully diapsid, which means the cheek region of the skull has two complete openings surrounded by bone, and they have at most a rudimentary hemipenis (the distinctive double copulatory organ that characterizes snakes and lizards).
Tuataras are a good example of an older group surviving on an isolated land mass, something typical of old islands like New Zealand, which separated from other parts of the former southern supercontinent of Gondwana around 80 million years ago. Tuataras had been spread about the globe during the Mesozoic (Age of Reptiles), but survived only on New Zealand.
It is distressingly common to see tuataras described as “dinosaurs”, but they are no such thing. They lived during the time of the dinosaurs (and have changed relatively little since, earning them the sobriquet “living fossils”), but their closest relatives are the lizards and snakes, together with which they form the larger reptilian group known as lepidosaurs. Dinosaurs closest living relatives are birds, which, indeed, are perhaps best thought of as actual dinosaurs themselves.
Thanks for the link to the page on bird origins! I’ve been trying to get across the idea that birds, not lizards or other reptiles, are the closest living relatives to my 8-year-old. Maybe this will help him picture what I’m talking about!
“I’ve been trying to get across the idea that birds, not lizards or other reptiles, are the closest living relatives to my 8-year-old.” Bloody heck!* What does that make you?
*A traditional greeting from the land of the tuatara.
As well as offshore islands, tuatara (sic, the plural is unmarked) can readily be seen at Zealandia, a sanctuary in Wellington surrounded by a predator-proof fence.
Bwahahaha! Interrupted mid-sentence by said 8-year-old, that’s what! Oh dear, well, I suppose, technically he *is* related to them… just not quite that close ;-))
Let’s just move that last phrase to a completely different place:
“…get across to my 8-year-old that birds (…) are the closest living relatives of the dinosaurs.”
Sumimasen! (and, thanks!)
A tuatara hatched at Zealandia last year, probably the first on the main since the introduction of rats centuries ago. “Tuataras” has long been the plural in at least non-New Zealand English, but, of course, longstanding usage can be incorrect (e.g. gharial vs. gavial). “Tuatara” is a Maori word meaning roughly “spine back”, so perhaps a Maori speaker could let us know what the plural should be.
GCM
I’m not a native speaker, but my Māori (2 years university, 40 yrs informal) is good enough for this. You show the plural by using a plural article; ngā tuatara, or a number; he tuatara e rua, two tuatara.
But to tell the truth, most non-Maori-speaking New Zealanders, which means most New Zealanders, would say two tuataras too.
…& we are all reptiles – cladistically.
Indeed!
GCM
Very kind of you, indeed, to defend so gallantly my glaring typo! (curtsying) ;-))
Cladistically all reptiles are fish (if “fish” has any meaning in cladistics it would have to be something like ‘vertebrate’) which means that whales and penguins really are fish and cats are reptiles.
Which shows how little our language and intuition has adapted to our insights into evolution.
And all vertebrates are invertebrates! But at some point this begins to sound like something written by Emmanuel Goldstein.
GCM
Nice, I missed that one!
Oddities like this are why I get uncomfortable with arguments that say “once a mammal, always a mammal” or “once a dinosaur, always a dinosaur.” I want to support these bird-dinosaur cladistic arguments but if we did this uniformly we’d find ourselves in a frightful mess.
Am I making a mountain out of a molehill here or am I missing some simple solutions? I don’t see this discussed much.
Since “fish” is a paraphyletic group, no mammals or reptiles are fish. We evolved from fish, and are sarcopterygians, osteichthyans, gnathostomes, etc..
The same can be said for invertebrates, since there’s no actual Invertebrata clade. Vertebrates evolved from invertebrates, and are chordates, deuterostomes, metazoans, etc..
Tyro– It is a bit of a mountain out of a molehill, but clear language is useful. For most paraphyletic groups (groups which are ancestral to other groups, which cladists don’t like), there are names available for the ancestor-cum-descendants group (i.e. the ancestor and the whole of its descendants; such groups are usefully termed holophyletic). So for reptiles, a paraphyletic group ancestral to mammals and birds, there is the group Amniota, which includes reptiles, birds, and mammals (i.e. the ancestor and all its descendants). Jawed fish are paraphyletic (because they gave rise to the non-fish tetrapods), but the term Gnathostomata covers both the jawed fish and the tetrapods. Which term to use would depend on what you might be emphasizing about them; I generally teach my students both (e.g., Reptilia and Amniota).
GCM
Technically, no. Reptilia is usually defined as the clade bracketed by turtles, lizards and crocodilians, so mammals are outside it. But birds are indeed reptiles.
A couple of things:
something typical of old islands like New Zealand,
Those deceptive Kiwis! First they call the Chinese Gooseberry a Kiwi-fruit, and now they advertise their beautiful country as the worlds youngest country! For shame!
hemipenis
Does that mean what I think it means? Half-penis?
hemipenis: Yes. They have two of them, one on each side.
GCM
How could you not mention the third eye? That’s my favorite thing about tuatara!
Ahhh. They are enlightened?
Isn’t he cute?
I’d love to have him as a pet. I’d feed him crickets and grasshoppers. That would be one happy tuatara.
Reptile eggs are so amazing. Imagine an egg that takes a year to hatch!
If only we could know what the tuatura lineage (nearest relative[s]) was like before being isolated with no predation. I mean, in terms of traits that allowed it to exist with predators, and that have now ‘relaxed.’
And no directed-evolution formed them per Lamberth’s atelic/telenomic argument!
Just to clarify about the Maori language. I am Maori and have been born and bred in New Zealand.
‘Tuatara’ is a Maori word; there is no ‘s’ in the Maori language therefore it would be wrong to say tuataras.
The correct way of pronouncing the plural would be tuatara. ‘There are twenty tuatara’.
Most New Zealanders, Maori or non Maori would know how to pronounce it correctly and would forgive foreigners if they pronounced it tuataras, however, I guess it’s more respectful to pronounce it the correct way.
Kia Ora Tatou