We're continuing our focus on Pleistocene fossils from Murrieta, California this week with a single bone fragment that has a lot going on.This bone is labeled in our collections as an ulna from Equus, a horse. It is indeed part of a left ulna, one of the bones from the forearm. More specifically, it's the olecranon process, the proximal end of the ulna that forms the point of the elbow. The triceps muscle attaches to the olecranon process, allowing you to straighten your arm (or front leg, in this case). However, after spending several hours comparing this to various publications and our Diamond Valley Lake collections, I'm not convinced it's a horse.For an olecranon process of this size, there are really only three likely animals from the Pleistocene of Southern California it could belong to: horse, camel, and bison. Everything else is either much larger (mammoth, mastodon) or much smaller (mule deer). (OK, to be fair, short-faced bears and ground sloths are in this size range, but their ulnae look nothing like this.) Horses, camels, and bison are all known from this site, but while it's a little on the small side, this bone is the best match with the western camel, Camelops hesternus.There is another interesting feature on this bone. Notice the four circular depressions near the tip (on the right). Here's a closeup:
There are a few comparable depressions on the other side:
These appear to be bite marks, from some carnivoran chewing on the end of the bone. There are several other scrapes that appear to be gnaw marks. So far we have not identified any carnivoran bones from this site, but they certainly made their presence felt.We have scanned and 3D-printed this bone (print shown below with the original), and the scans can be viewed on Sketchfab at https://skfb.ly/6xNMM.