Fossil Friday – mastodon rib


Here at Valley of the Mastodon, we’re ringing in the new year with a rib from our namesake animal. Ribs don’t often get a lot of attention, but there sometimes is information that can be gleaned from them.

The left rib shown above is incomplete, with portions of both ends of the bone missing. The proximal end, closest to the vertebrae, is to the right. This rib is large enough to be from an adult or near-adult animal, but it’s impossible to estimate the age with any certainty. Ribs do have an epiphysis at the proximal end that is unfused in young animals, but that area’s not preserved in this specimen.

So what’s going on with the proximal end of this rib? Here are some closeups from various angles:




A swollen region around the bone, pits and bone spurs on the surface…these are all indications of an injury or other pathology. As with many of the specimens in our current “Stories from Bones” exhibit this bone shows a healing response to some type of trauma. It’s difficult to say what the trauma was. The bone could have been broken in an attack by a predator, and while there are no indication of bite marks to corroborate this it’s still a possibility. The rib could have been broken in a fall or some other accident, or in a fight with another mastodon. Infections and certain diseases can also sometimes cause this type of response in a bone, but we are definitely looking at something that happened to this mastodon while it was still alive.


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