Jen here-
Once I have identified the structures, I can trace each one! I use a drawing pad and it can actually be quite relaxing tracing the folds. But it takes a lot of time and we have thought about figuring out how to make the computer do it for us but in some cases the outline is faint or you can see extra folds that are not actually part of the layer you are on. This happens when the slices of the fossil are taken not exactly perpendicular to the long body axis. The slices that I am working with were made in the 1960s and were done by hand so it is common that they are not exactly perpendicular.
In the video below you can see me tracing the hydrospire folds on a slice of Pentremites pulchellus. Once we trace all of the folds we were interested in, we can hide the images of the slices and all that remains are a series of stacked line drawings. We use another program to create the three dimensional structures.
Citation: Dexter, T.A., Sumrall, C.D., and McKinney, M.L 2008. Allometric strategies for increasing respiratory surface area in the Mississippian blastoid Pentremites. Lethaia, 42, doi: 10.1111/j.1502-3931.2008.00110.x
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