A mystery tooth

 

During our Mastodons of Unusual Size road trip, we examined a large amount of material that couldn't be included in our dataset. In most cases this was because the teeth were too damaged to take accurate measurements, but in a few cases it was because we couldn't determine where the tooth came from, and our study depends on that data. While all the museums we visited have excellent collections standards, some of these institutions have been around for a century or more. Standards have changed over time. Sometimes in the past locality information wasn't retained, or in the case of some donations, may have never been collected in the first place. 

The nicely preserved lower 3rd molar shown here is in the collection at the Boonshoft Museum of Discovery. As we've worked on this project, we've found that the California-style tooth is so distinctive that we can usually recognize it right away, and this tooth caught my eye. Unlike all the other teeth in the Boonshoft collection (which were mostly from Ohio and Kentucky), this tooth looked like a California tooth. Unfortunately, it does not have any locality data at all, so we don't know for sure where it came from.

When I say it looks like a California tooth, what I mean is that it's relatively long and narrow in occlusal view, and that overall the tooth is pretty small. Even though we couldn't include the tooth in our data set because of the lack of locality information, we still took measurements to see where it fits. The graph below shows width vs. length measurements for lower 3rd molars. California teeth are in blue, and the mystery tooth is marked with the black "X":

 

As you can see, the California teeth cluster together, and the mystery tooth falls out very close to the California cluster, although it's a little on the small side even for a California tooth. Its length:width ratio is 2.22. The average for California is 2.30, while the average for non-California teeth is only 1.91. This would be a surprising find if it came from Ohio or Kentucky like most of the Boonshoft collection.

As I looked at the tooth more closely, besides its proportions there were some other interesting features. I particularly noticed a black, irregular deposit covering parts of the crown:

 

This looks a lot like residue found on specimens that come from the tarpits at Rancho La Brea in California, as with the glob of material stuck to this specimen from the Page Museum:

 

Could this Boonshoft tooth actually be from Rancho La Brea? Here's where it gets intriguing; the Boonshoft Museum actually has a small collection of Rancho La Brea specimens! There is one drawer in the museum that includes material from Canis dirus, Smilodon, and Paramylodon that are all from Rancho La Brea; apparently they were acquired by the museum back in the 1920's or 1930's. I suspect, but can't absolutely prove, that the mastodon tooth was part of the same Rancho La Brea collection.

OK, to be clear, if we took a sample of the black material and compared it chemically to material from Rancho La Brea, we probably could determine if that was its point of origin. But that would be a relatively expensive and time-consuming project to simply add a single tooth to our dataset. Perhaps some geochemistry student looking for a project may take it on one day!