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Leaving My Leaves

I spent most of the time since my last blog post taking pictures. Pictures of whole leaves, pictures of cells, pictures of stomata, pictures of veins. As a reminder, I’m looking at leaf diversity from a few sites from the Early Cretaceous of Mongolia, about 120 million years ago. I used the scanning electron microscope at the Field Museum and the compound microscope in our lab to get epidermal details, like the cells and the stomata, and luckily by separating the leaf cuticles before scanning we turned our difficulties with the SEM around. I was able to use all of these images to finish compiling sets of data for each leaf type and finalize how each morphotype was defined.

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The organization of the stomata on each leaf and venation were the most useful characteristics to define the morphotypes. For example, a few of the leaves only had one primary vein (Morphotypes 3, 4, 6, and 9), so we knew with confidence that they were different from Morphotypes 1, 2, 5, and 7, which have multiple or no visible veins. After that we could differentiate between all the single-veined leaves because their stomata are arranged differently. Morphotype 3, for example, has two lines running along the midvein, which turned out to be lines of stomata, whereas Morphotype 9 has very few stomata that are located across the leaf surface. We made decisions like that for all seven morphotypes from Tevshiin Govi and for two from Tugrug (Morphotypes 8 and 9).

With the finalized morphotypes we were able to compare the leaves to known leaf types using a handy paleobotany textbook and some previous studies from the literature (below). Unfortunately, this turned out to be very difficult and actually impossible for some morphotypes because we just didn’t have enough characters. Despite this, we were able to make some connections and together with all my morphotype data could turn my work into a poster to share with others. Hopefully my findings will be useful to those who are continuing the Mongolia project and need to put all these different kinds of fossils together into whole plants.

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 Morphotype 5 with Podozamites sp. from Krassilov (1982. Early Cretaceous Flora of Mongolia. Paleontographica B 181: 1-43).

In my last week at the garden I also had the opportunity to accompany my mentor to Argonne National Laboratory where they used x-rays to reconstruct the internal anatomy of some of their more three-dimensional fossils. This is a very slow process but has some amazing results! The building also looks like some kind of crazy lab from a sci-fi movie, which was pretty cool. This week was also the first chance I had to really explore the entire garden, rather than just little bits of it during lunch. Sadly this made me realize how beautiful it is and how much I’ll miss it! But I’ll just have to come back to visit. On our last day we had the joint Undergraduate Research Symposium with the Field Museum and Morton Arboretum REUs at the Field Museum. It was great seeing what everyone else was working on and how much could be accomplished in just a summer, as well as getting to share my work with others.

Now that my internship is over and I’m back at school, I am extremely grateful for the opportunity and the preparation it has given me to do independent research here. I am also endlessly grateful for all the people I met both at the garden and among my fellow interns, and for solidifying my interest in a paleontological career!