Last week we started a new preparation project, a roll-out cart where we do fossil prep work on the exhibit floor. Our first project for the cart is a jacket containing a series of bison vertebrae.
The way the jacket has been opened, the vertebrae are exposed on the left side, so they’re seen above in left-lateral view, with anterior to the left. As I mentioned a couple of weeks ago, mammal backbones are generally divisible into five different regions based on their position and particular features.
This small sequence actually contains vertebrae from three of the five different regions, as shown in the annotated image below. Bones outlined in red are thoracic vertebrae, those in blue are lumbars, and the ones in green are sacrals and the associated hip bones:
Typically, bison have 14 thoracic vertebrae. We have part of the last one, the extra neural spine at the front of the jacket. We also have part of the main body (the centrum) of this vertebrae, but it’s separated from the jacket.
Bison generally have five lumbar vertebrae, so we have the entire lumbar series preserved (compare them to this image of a modern bison lumbar series, shown in dorsal instead of lateral view). We are missing the long transverse processes that should be sticking out of the left side of each vertebrae; it’s not unusual for them to break off before burial.
Bison also have five sacral vertebrae that are generally fused to each other and to the hip bones (at least in adults). We have at least the first sacral vertebra, and some additional portion of the sacrum, but that area is still kind of a mess and it will be awhile before we know exactly what’s in there.
I’ll be posting periodic updates on our progress with this jacket as preparation continues. The preparation cart is currently on display at Western Science Center from 10:00-12:00 on Tuesdays, with additional times to be added soon.