Fossil Friday – Max the mastodon’s mandible


If you follow the museum’s social media pages, you’ re probably noticed that last Tuesday we had an adventure with one of the museum’s mastodons, Max. We pulled Max’s lower jaw off exhibit and, via ambulance and with a police escort, sent him to California Imaging and Diagnostics in Hemet for X-rays and CT-scans. There were several reasons behind this effort, but the primary one was that Max’s jaw shows evidence of several injuries that we wanted to further explore.

Max leaves the museum amid a crowd of Western Center Academy students.

Preparing to load Max into the ambulance. 

One of Max’s injuries is very obvious and we’ve known about it for some time. There is an anomalous bony growth at the right anterior tip of the jaw:


The ridge anterior to the teeth on the dorsal side of the jaw is also rather misshapen in this area, possibly related to the same condition.

The second injury was first spotted a few months ago, and was actually first observed in a cast we were making of the jaw; in the original specimen the injury was hidden due to the case structure and lighting the exhibit. This injury is a 2 cm-wide groove, running diagonally along the right dentary below the second molar. There are ridges of swollen secondary bone (a healing response to a bone injury) on each side of the groove:


We’re still processing the data gathered at CID, and I’ll have more on that (including images) in a future post. But there are already some things we can say about these features, starting with the fact that they occurred while Max was still alive, at least weeks or months before his death(and possibly years before). That’s because both feature show evidence of bony growth, and it takes time for that to occur. Evidence of healing is the most reliable method of determining whether a break in a fossil bone occurred before or after death.

Max is a large mastodon, the largest reported from California. Given the size and the massive tusks it’s probably that Max was a male mastodon. That, and the fact that he was a mature adult (based on tooth wear), suggests a possible cause of these injuries: intraspecies combat. Like modern elephants, there isabundant evidence that male mastodons engaged in intraspecies combat (see Fisher, 2009 for example), often resulting in injuries, sometimes fatal injuries. It’s possible that both of these injuries, especially the groove on the side of the jaw, were caused by the tusks of another mastodon.

Reference:

Fisher, D. C. 2009. Paleobiology and extinction of proboscideans in the Great Lakes Region of North America. In G. Hayes (ed.), American Megafaunal Extinctions at the End of the Pleistocene, Springer Science: 55-75.

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