Early tetrapod feeding

Well, I’ve managed to fail at my scicomm resolution for the year, which was to write at least one blog post a month. I missed out on September, but I’m back on it in October with an update on what I’ve been up to in the past few months.

As some of you know, I’ve been spending a lot of the past year since finishing my PhD working off-and-on in an arthritis research lab, looking at CT scans of zebrafish. I learned a lot working on fish, and have enjoyed it, but it wasn’t something I could do forever. While I’m still finishing off a few things for them, my contract officially ended a few months ago.

However, I’ve managed to find myself another contract! This one is another short term contract, but it’s 6 months part-time, and it’s back on fossils. For the next six months, I’m working on a project with Laura Porro and Emily Rayfield on the evolution of the skull in early tetrapods, through the water-to-land transition. I’m working for a few months on some CT scans of some of the earliest tetrapods in order to understand how the skull and feeding system changed as animals went from water to land. Specifically, I’m doing the 3D reconstruction of the skull of some animals called embolomeres, which lived in the Carboniferous of Scotland. These animals were terrestrial rather than aquatic, and likely amphibians rather than amniotes.

CT scan surface of Eoherpeton watsoni, showing the well-preserved right side of the face and top of the skull.

These are the most derived animals that we’re looking at in this study, and despite being approximately 320 million years old, the skulls are in pretty good shape. In the animal I’m looking at right now, Eoherpeton watsoni, the skull is still articulated in much of it, with most of the bones easily identifiable and in position. Unfortunately, the skull is crushed, as you can see from the photo above. In order to do any analysis on this and to really understand the skull shape, I’ll need to reconstruct the areas that aren’t preserved, and retro-deform it into something like it’s original shape.

So my job for the next 6 months is going to be to identify all the bones in the skull, then reconstruct any that are broken or missing pieces, and then to move elements around so it’s 3D again. To do this, I’ll have to mirror elements from one side (the right) to the other (the crushed left side). But I’ll also combine some elements to make a complete side – for example, the right side of the lower jaw is well-preserved at the front and back, but missing some in the middle. The left side, however, has most of the middle, but is poorly preserved at the front and back. With these combined, we get a whole jaw!

I’ll be following the methodology and structure used by Porro et al. (2015) where they did something similar with the skull of a very famous early tetrapod Acanthostega gunnari. They started out with a not too bad skull:

Skull bone diagram of Acanthostega before retrodeformation, displaying the bones as they sit currently in the fossil. From Porro et al. (2015).

Laura was able to retro-deform the skull by moving bones into more life-like positions by looking at the contacts between bones. This resulted in a less pub-like/squished reconstruction of the skull:

Retro-deformed 3D reconstruction of the skull of Acanthostega, from Porro et al. (2015).

And finally, in order to really illustrate the sutures and contacts between all the bones, and to show the individual shapes of the bones more clearly, she also made the awesome exploded diagram of the skull:

Exploded Acanthostega diagram from Porro et al. (2015).

It’ll be a long road for me since I haven’t done such detailed CT work before, but I hope that at the end of this I can have some diagrams like these ones of at least two early tetrapods. It’s been a lot of fun so far to learn about early tetrapods, both their anatomy and just generally what we know about them. I’m looking forward to learning more about them, and hopefully making some cool reconstructions!

So while I’m still not a proper “post doc”, I am doing some cool postdoctoral research. I’m happy to be getting paid to look at fossils, and have some more cool projects that I’m working on over the next few months. Hopefully I’ll be able to find some funding at some point to get an actual post doc of my own, but in the meantime, I’m just happy that I’ve been lucky enough to find some work looking at fossils.

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