Saturday, March 19, 2011

Day 4: Sitting under Skeletons

Rainy day on the Limmat
The weather today makes me almost forget that it is mid-March and I am on spring break. It is overcast and rainy today, but Zurich wears it well. I cross the Limmat river each day on my way to and from the train station, and the view across the water has become one of my favorite sights.
View across the Limmat River
I have not had much time to explore the city since I am at the museum during the day and do not stay out late at night as a rule of common sense, but my hotel is near the tram stop Central in the old city, and I get to see views like this as a part of my daily commute.

Today my research centered on the specimens Sarah and Moritz. I took photographs of these dinosaurs and measured their limb bones, which has become routine as I move from specimen to specimen. I had the time to start taking photographs of Lilly too, who is mounted in the middle of the room on a raised platform, making it somewhat difficult to get a good straight-on shot. Lilly is mounted in simulated matrix, giving the specimen the appearance of being exposed on the site, although it has been fully prepared and the individual bones are removable from their resting spots in the display. Unfortunately, I may not be able to access this specimen because of the surrounding display components, but I tried to get as many photographs including a scale bar as I could.

Sarah and Moritz proved much more straightforward subjects. Sarah, whose virtues I expounded in my last post, is a freestanding mount, and thus simple to measure and photograph. Moritz is another freestanding mount next to Sarah. Moritz is the least complete of the four specimens, but the limbs are mostly original bone, which proves useful for my study. This specimen is not very helpful for determining information about the plates or spikes, though, because most of them are missing.

Hesperosaurus mjosi "Victoria" Right hind limb, compressed
One important fact that I need to take into account while conducting my measurements, which was pointed out to me by Dr. Siber, is that the compression of the bone during the fossilization process can warp or distort the dimensions from the original. In the prep lab, Dr. Siber showed my a set of several articulated vertebrae that had been compressed, so that all of the centra were flattened at an angle. This kind of visible compression creates discrepancies in the measurements, and can be seen in the stegosaur Victoria. As a result, the right and left side measurements are not exactly the same for this specimen. This kind of result, when taken out of context, can lead to misidentification of which elements belong to which individual, and can even result in the creation of new species unnecessarily based on morphological differences that are ultimately taphonomical in origin.

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