Volunteer Joe Reavis been hard at work on a collection of fossils from a mitigation project in Murrieta that includes a lot of mastodon material. As far as we can tell so far, all of the mastodon material is consistent with one individual, although we did confirm yesterday that there is non-mastodon material in the same collection.
The specimen shown above is a molar from a mastodon. It’s in pretty rough shape, but I think it’s the upper right second molar. If that’s correct, then the occlusal view above has anterior at the top, and the lateral side of the tooth is on the left. The three loops of enamel on the left are the remnants of three lophs, which indicates that this is either a 4th premolar, 1st molar, or 2nd molar (the 2nd and 3rd premolars only have 2 lophs, and the 3rd molar has 4 or 5 lophs). The length of the tooth is comparable to other 2nd molars in our collection.
Upper teeth in mastodons wear more rapidly on the medial side than the lateral side. If we look at this tooth in lateral view, we can see that there is a only about 2 cm of enamel remaining; the rest of the lophs have been worn away:
In most animals this would indicate that the animal was very old, but the horizontal tooth replacement in mastodons and most other proboscideans changes the equation. The 2nd molar typically wears away and falls out sometime around age 40 (very approximately). This tooth still had its roots (they were broken post-mortem), so this mastodon was probably around 40 years old when it died.