Now that is definitely bone - not sure if from a skull or something like a scapula fragment or similar. I think the deep grooves may actually be worm bores or similar. Could even be from a dugong, in SC…
…but note how texturally and petrographically, it’s completely different from the OP’s find.
It is hard to tell from the out of focus images, but take a close look at the cross section photos for the OP’s piece–while it is mostly smooth, there are small pits scattered across the surface. Manatee bones would be very dense (for buoyancy reasons) so I did a google image search for Manatee rib cross-sections and found this post, which confirms what I was thinking.
(For comparison, here are some random bone fragments I’ve found on South Carolina beaches–most of the look more boney, but the one on the lower right is more similar to the OPs. (This one isn’t boney at all–just bragging about a nice small piece of fossil wood.))
Looks like weathering, not structure, to me.
That piece has a very clear grain, and isn’t vitreous at all.
I’m not saying the OP’s piece* can’t *be a manatee rib (fossilization isn’t an exact process after all), but it doesn’t look like the other fossil bones I’ve seen (and I’ve seen plenty) - it’s particularly the vitreous lustre and lack of grain that are different.
I relayed the ID question over to TheFossilForum (probably the best site for fossil discussions) and got this:
*Well then you can relay to the finder that this bone is quite definitely a sirenian rib fragment as thought. In particular it is from the now extinct species called the Florida Sea Cow (Metaxytherium floridanum). These bones do not have the spongy cancellous (trabecular) inside which normally contain bone marrow in other bones and are instead solid right through to the core. This makes them preserve very well (so they are common finds in the Peace River) as well as making them very distinctive to identify. More information may be obtained here: *
Coincidentally, there is a thread about fossiling on the Peace River posted there less than a day ago.
Cool, good to have an expert opinion.
Excellent! Thank you
I might post pictures of the bone fragments I found as well in the same gravel pile.