SVP is next week! Plus additional analysis!

The SVP conference is next week, and the Mastodons of Unusual Size poster is printed and ready to go!

Our poster presentation is essentially a status update, as we're still adding more data as it becomes available and working on interpretations. One reference I was eager to read was J. J. Saunders' 1977 paper "Late Pleistocene Vertebrate of the Western Ozark Highland, Missouri". This paper doesn't seem to be available online, so I had to mail-order a copy. This work includes descriptions of the Trolinger Spring and Boney Spring faunas, both of which have numerous mastodons. Since we have very little Missouri material in our dataset, this would make a nice addition.

Alas, it was not to be. While the Saunders paper is a nice work with a tremendous amount of detail, it does not include length and width measurements of the individual teeth, which is what we need for our dataset. While this is frustrating, I can't criticize Saunders for this; it was not common in the 1970's to include detailed raw measurements in a printed publication. They take up huge amounts of space, and printing on paper is expensive. In the digital age, it's much easier (and cheaper) to make that data available, and we intend to do so on our project.

At any rate, while Saunders didn't publish his length and width measurements, he did summarize them and graphed the individual teeth on a length vs. width plot. Below is his plot for lower 3rd molars from Boney Spring (just a photo shot on with my phone, so it's not the highest quality):

 

Just for fun, I sketched onto this graph the average length:width ratio for mastodons in our dataset for locations outside of California (and Idaho, which look like CA). That average (1.91) is indicated with the yellow line:

 

Any tooth that plots above the yellow line, toward the upper left of the graph, is wider for its length than the average tooth. A tooth plotting below the line is thinner for a given length than average. The Boney Spring teeth plot very close to the non-California average, maybe very slightly on the thin side (because of the way the data is reported, I can't compare the averages exactly).

So how would the California teeth look on this plot? The blue line is the average ratio for California (the 2 teeth from Idaho have the same average as California):

 

Nothing from Boney Spring is even close to the California average (the California teeth are really skinny!). The Trolinger Spring data looks very similar to that from Boney Spring, so if we could this to our dataset it would just serve to reinforce the trends we already are seeing. Incidentally, the blue line is dashed above 200 mm length because no California tooth longer than 200 mm is known, so there are 9 teeth from the Boney Spring site that are longer than any known California tooth.

Here's another neat example of how weird the California teeth are:

 

The red dot is about where the thickest California tooth we've measured would fall on this graph (the dotted red line represents that tooth's ratio, 1.95). Most of the Boney Spring teeth are thicker than even the thickest California tooth known.

One final point; this is all just an approximation based on a very quick look at Saunders data, and actually oversimplifies things a bit. For example, on this we're looking at is the slope of the average line. The way I've plotted it here, I'm assuming that as a tooth gets larger that the proportions stay the same. In other words, for an eastern mastodon, the length:width ratio is going to be close to 1.91 regardless of how long the tooth is. For the Boney Spring mastodons that is pretty much true; they all plot pretty close to the yellow line. However, for California mastodons that may not be the case. It seems that CA teeth may get longer faster than they get wider, so the ratio would be greater for longer teeth. That means that the blue line on the graph should be closer to horizontal. In fact, the widest tooth known from California only has a width of 88.9 mm; it happens to be the tooth marked with the red dot, which is far from the California average.

I'll have more to post after the SVP conference next week, and don't forget to follow valleyofthemastodon.wordpress.com as well as @MaxMastodon and @AltonDooley for additional updates.