Question: Are axolotls dinosaurs?

[paws4eva]

Just curious-

Does anyone know how old axolotls are? What period the first appeared in?
Are they as old or older than the dinosaurs?

 

[esn]

Well, no. They're not dinosaurs. But they are pretty darn old. If you're interested, you ought to read the book titled Your Inner Fish by Neil Shubin. It's a great book.

Let me give you a run down.

Neil Shubin and his team discovered the link between fish and amphibians - a fossil in the "inbetween phase" found in rock dated to be 375 million years old. The first aquatic life is dated to be in the Palaeozaic era, which started 570 million years ago.

This is about 15 million years before the Carboniforous period - that is, the period that we see the first fossils of reptiles which are not yet dinosaurs (they come in at the Mesozaic era, about 130 million years later).

Neil's fossil, Tiktaalik, or "large freshwater fish" in Inuit, is a "fish" fossil that has a neck and specialized fins, resembling limbs. This is a cross between fish and early tetrapods, and is basically the link between the larval state of amphibians and their terrestrial state, and the link between fish and reptiles as a whole. Not only that, but it is the animal that was the stepping stone to terrestrial life, eventually evolving over the many millions of years to finally come to us humans.

There is a lot more history in the book, but those are the basics. Amphibians, salamanders in particular, came before dinosaurs. They're not dinosaurs, but something far far more ancient! It is also interesting to note that newts and salamanders have not changed very much from their ancestors, compared to other life forms.

Here's a cool little timeline for you:
Dinosaurs Timeline

If you want to learn more about just how cool salamanders are for developing the first limbs and walking on land, definitely read the book I mentioned! The author covers a lot more stuff, and goes into anatomy changes over time in great detail. It's a comprehensive look at the transition from sea life to land life.

Axolotls individually have only evolved (excuse me if I'm wrong) in the last 10,000 (maybe 20,000) years. They came from tiger salamanders, as far as most people figure. They're babies, evolutionarily. But they have impressive roots.

 

[esn]

Oooh, I just realized the author has his educational slides up on the UChicago site!

Your Inner Fish: Teaching Tools

Very good stuff there, and his pictures illustrating the anatomical changes through evolution are very simple and easy to understand. Not to mention they can be slightly amusing at times.

I think it's also a pretty convincing approach to true Darwinian theory - nothing says "Evolutionist" like writing a whole book about how humans came from fish!

Here's my favorite image - you can't beat the illustration of the fossil record, haha.

 

[Azhael]

I would like to make a small comment. Modern amphibians are highly derived forms, most may share the basic tetrapod morphology of early labyrinthodonts, but so do most reptiles. I think a looooooot of people have a concept of early tetrapods that basically makes them amphibians as we know them and that there has been little change but that´s just not the case. Early tetrapods probably looked more crocodile like than amphibian like, with scales and larger teeth. The modern amphibian skin is definitely very derived as are many other characteristics, not to mention non-typical groups like all anurans, sirens, amphiumas, caecilians, etc.
Sorry for nitpicking xD but i couldn´t resist. Salamanders didn´t develop the first limbs and crawled onto land, they only appeared well after amniotes had appeared and diverged into synapsids and reptiles. They may not be the oldest, but they are still the coolest