On when you don’t uncover a clear answer

Sarah here –

Last summer, I went to southern Indiana to do some fieldwork with my undergraduate research student, the wonderful and intelligent Sarah Johnson (who has since graduated and gotten an excellent job working at an environmental consulting firm in Texas). We went there to collect data to answer a really intriguing question that, I am very sorry to report here, we still do not have an answer to. This post is about fieldwork, undergraduate research, and even more importantly, the importance of reporting the experiments and the field expeditions that just didn’t work out.

I work on a group of unusual extinct echinoderms, the diploporitans (you can read more about them here). One of the many weird things about this group of echinoderms is that no one can find fossil evidence of them as juveniles- we only find them as adults. All living echinoderms have a free-swimming larval stage- meaning, even the echinoderms that don’t move much as adults (like crinoids) are quite mobile as juveniles! For other groups of fossil echinoderms (like blastoids), there are plenty of examples of very small juveniles that likely moved the way that modern ones do-as larvae. However, there’s no known fossil evidence for this in the diploporitans.

This is a specimen of an adult diploporitan, found near Napoleon, Indiana. We spent a lot of time this past summer looking for juveniles, but unfortunately, didn’t find any.

So my student, Sarah, and I went to the one place in the United States that we would expect to find juveniles, if there are any to be found- Napoleon, Indiana. The reason that we would expect to find juveniles is that there are a very large number of preserved adults there-which makes it more likely that smaller ones would also be there (too small to see with your eyes). Sarah and I searched the outcrop for hours looking for the areas that had the highest density of fossils, collected about 50 lbs worth of sediment, and drove back to Knoxville, TN.

Sarah and Russell Godkin, my other undergraduate research student, then spent the rest of the summer sifting through the seemingly endless buckets of sediment that we brought back-they used microscopes and analyzed the smallest sediment grains for all fossils. They pulled out thousands of tiny corals, brachiopods, and pieces of crinoids. However, after countless hours, they didn’t find a single diploporitan juvenile-not. a. one.

Obviously, we were all quite disappointed-we really wanted to find these fossils (and Sarah and Russell were really tired of looking into microscopes-but I digress). There’s an important lesson in here, though- the LACK of an answer is just as important. The lack of an answer can help us develop new hypotheses as to why we can’t find these juveniles and it can help other scientists better understand related questions about echinoderms and fossil preservation. So-never fear, the hunt to figure out what juvenile diploporitans looked like is still on!

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