Eye bones

Strange Obsession with Bony Eye Rings

Ever one of those head-tilt ponders while staring at something that suddenly becomes very fascinating, all the while you're whispering in your head, "What the fuck is that?"
I'd like to call those puppy thoughts, because whatever you're staring at is just as interesting and thought provoking as an adorable baby dog trying to understand the noise coming out of that chew toy. With all your millions of years of evolution, you suddenly become reduced to a head-tilt, all the while your brain swimming with questions.

Anyone who enjoys looking at bones of dead things may have noticed these extremely odd and unique bony structures around the eyes of certain animals, almost resembling bony rings surrounding the eye socket. These odd, almost robotic looking rings are typically seen in reptiles and fish, but not mammals and crocodiles. I figured they had something to do with the eye function, like perhaps how they attached to the skull or had to do with how they focused the eye because of the camera lens like structure.
That was my guess, but I wasn't exactly right.

• Sidetracked: Eye Evolution

Before diving too headlong into these weird eye adaptations, I think it's a good idea to familiarize yourself with the evolution of the eye, because it is one of the most impressive organs to be forged through the ages. Often the weapon of creationists, the eye in all of it's complexity as been a beautiful enigma for scientists for centuries. The squishy, fluid balloons that sit in your skull have the power to drink in the world around you and flash the images to the wrinkled mess operating your body. How can something so amazing, so oddly specific in it's function come to be?

There's is a misused and misquoting piece of Darwin's Origin of Species that is often haphazardly tossed into arguments against and for evolution that is often brought up when it comes to the human eye:

To suppose that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree.

Plucked out of context, this sounds like Darwin helps the "designer" argument for the complexity of the eye, which is not at all how he viewed the subject.
If you want to check this yourself, you absolutely can in chapter five of Origin of Species, but the quote goes on as follows:

Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real. (Darwin 143-144)

 So, how did eyes evolve into the glorious, often beautiful, complex windows into the world? It's Okay To Be Smart did a series on evolution back in December called 12 Days of Evolution, which I've gushed lovingly about before.
In this particular episode, they go on to talk about the evolution of the eye from humble beginnings into the amazing variety ones sees today. I also very much recommend watching the amazing Neil DeGrasse Tyson's Cosmos, as he very eloquently talks about this process in his storytelling, magical narrative.

• Eye bones: What the hell are they?

The bony structures are called Sclerotic Rings, and they are still somewhat of a mystery. The rings are apparently still found in modern day birds and fish, but the exact function of the rings is still debated. From the couple articles I looked through, it seems the rings most likely are for helping maintain the shape of the eye, especially for larger eyes of marine reptiles.
Some of the best examples of well preserved sclerotic rings are that of Ichthyosaurs, a large marine reptile that looks like a doe-eyed dolphin. In an article from UC Berkeley, a certain species of Ichthyosaur, Temnodontosaurus, had the largest eye ever recorded for any animal. These rings probably helped these massive eyes keep their shape and structural integrity.

Speaking of marine reptiles, I'm sure most people know about Mosasaurs from being the giant badass Shamu attraction from Jurassic World, but these guys also had some pretty impressive eye bones that have been heavily researched.
A team of researchers from Tokyo Gakugei University published an article on PLoS One about how they are using the rings to help classify species of Mosasaurs between one another. Since this is a peer reviewed scientific paper, it's pretty scientific term heavy and dry, but it's pretty fascinating to read.
Along with the common assumption that the rings had something to do with the maintaining the eye's shape, the rings may also have served as "providing the point of muscle insertions fr visual accommodation", like I had thought originally. Score one for me!
What I didn't know was that the rings also may correlate to whether or not dinosaurs were nocturnal, which is really interesting. I went hunting for the paper referenced in the PLoS One article about this claim, but it's unfortunately not available online. It's most likely one of those papers you have to pay for, which is a bummer. I'll keep digging around and maybe do another blog post when I can find more material on the subject, but the idea of nocturnal dinos sounds pretty cool.

From what I've gathered through my couple hours of poking around the internet on a whim, these unique eye bones, or Sclerotic Rings, still have some research to be done by much more brilliant minds that myself.
I think the next thing I want to dig into is going to be the purpose of sails on dinosaurs and other early life forms. I think the research for that is going to be about the same as the eye rings, a lot of great and strange ideas worth sorting through with the hopes of one of them making sense.
I also need to be a certain dinosaur to do research on and make a post about, and have a couple in mind I want to fan-girl out over. Maybe a monthly recap is in the future too.
We'll see.

Until then!

-M



Sources of my internet poking:

UC Berkeley article about giant eyed Ithyosaurs

PLoS One talking about Mosasaurs