I found this reasonably well preserved partial sacrum (which I assume is either mammoth or mastodon), in the Brazos, a week and a half ago.  It is finally dried out and I was able to treat it with paraloid.  It was extremely fragile when found it.  Size is about 290mm, 11.5 inches left to right in the photos.  Is there any way to tell if it is mammoth vs mastodon?  I've found both in this spot. I've not been able to find good images online, particularly for mastodon and nothing that describ