As we continue our month of mastodons in support of our crowdfunding campaign at experiment.com, this week we have a partial mastodon skull from Diamond Valley Lake.When I say partial, I mean very partial. Practically all that's left of this specimen are the upper teeth and one tusk. Almost all the bone is missing, a somewhat odd preservation type that we get occasionally at Diamond Valley Lake. We haven't taken measurements on the tusk, but it seems to be massive, suggesting that this might be a male. The skull is laying upside down, and oriented so that anterior is toward the camera (this large jacket was sitting on a storage shelf, and would have been difficult to move quickly to get Fossil Friday photos in other orientations). The two upper third molars are visible, but there's no preserved trace of the second molars. The crowns of the third molars are well preserved, so this is a specimen we'll be able to include in our study. Every loph on the molars is in wear, with the last lophs just starting to wear, so this animal was presumably a bit older than Max (who still had second molars and unworn last lophs on the the third molars).We have just under two weeks to go in our crowdfunding campaign to gather data on mastodon tooth shape from localities across the country, and we still have a long way to go, so please visit experiment.com/mastodon and give what you can to help us with this study.