Turtles: they aren't true reptiles.

I'm just going to jump right into this. Firstly: Testudines are anapsids. Anyone who lumps them in with Eureptilia is a total moron. They lack the Diapsid condition and are clearly holdovers from the ancient Anapsida. I see absolutely no reason to assume they are diapsids that simply closed their temporal fenestrae- it is, in my rather humble palaeontological opinion, silly to assume they have those origins. I've been demonstrated to be wrong before, so it'd be cool if that happened, but I am highly skeptical. I lean heavily on Procolophonid ancestry for testudines simple because the skulls look so shockingly similar and they are a lot more similar, as far as I can tell, than any of the other proposed groups for testudine ancestry. Keep in mind I'm not alone in this opinion, so it's not like I'm blowing smoke on this.

So I bring this up as a bit of background to my upcoming diatribe on testudines themselves. Honestly, this group is fucked up. A toothless beak, jaw muscles that insert on the INSIDE of their damn skulls (as opposed to the outside like other "higher" verts), a shoulder girdle that develops originally outside of the rib cage and then, ontogonetically, rotates INSIDE the ribs, dermal bone connecting the ribs on top and bottom, an uncanny ability to slide the neck, head and limbs inside the rib cage and of course the ability to poop out their tail (hah).

This group may be fucked up but it is also a bit of a mystery. Until the recent discovery in China, the first turtles in the fossil record were quite literally already turtles and the only hints at their origin came from similarities in other groups. We didn't even know if they were aquatic or terrestrial in origin or if the plastron or carapace evolved first! Well, at least we have Odontochelys, or "toothed turtle" to look at. That name alone should be a big hint that it is a turtle with teeth- showing just how plesiomorphic it is (as if having only a plastron wasn't enough to tell you that).

The relative timing and process, at least as far as I am aware, of the shoulder girdle moving inside the ribcage is a bit of a mystery, though genetics, which are not my field, will likely tell a bit about the process and probably already has. The problem with this group is that even with Odontochelys, we still don't know where the hell they came from.

To compare to other reptiles, we have limbed snakes that betray their true location within the squamates- snuggled in with monitors and mosasaurs and not near Amphisbaenia. We know where the eureptilian tree shakes out, more or less, as we do with lissamphibia (though it does look like caecillians are more close to microsaurs, an ancient amphibian group. While we are on that topic, amphibian is a hideous waste basket term much like reptile. The amphibians today may be old, but they aren't the same thing as ones from the Devonian. If we are using that logic, then pretty much every tetrapod is an amphibian. Lissamphibia may be the most similar to that group, but that doesn't mean they are the same.

So what becomes of our turtley pals? Well, they aren't getting their due credit as a truely ancient survivor that is likely one of, if not the, oldest relatively unchanged tetrapod group on the planet. It saddens me to some extent that they are so callously lumped in with lizards under the generic "reptile" umbrella when birds are so much closer to being true reptiles than testudines are.