Sharktooth Hill bone with peculiar indentions

[ScottM]

Hello,

The indentions in these two pieces of Sharktooth Hill bone are very unlike anything else I've found there and I'm hoping someone recognizes them. Very smooth and very round, about 2-4 mm deep. I'm including pics of the backs of the pieces, not because they seem interesting, but just so you can see that they're not. It's a little hard to tell, but the large piece has a partial indention on one of the broken edges on the right side of the pic. Thanks for any insights you can offer!

 

Larger piece - Front

 

 

Larger piece - Back

 

 

Smaller piece - Front

 

 

Smaller piece - Back

 

[Brett Breakin' Rocks]

1 hour ago, ScottM said:

Sharktooth Hill bone

@caldigger may recognize them specifically ... but we often get something akin to Piddock clams ... boring mollusks, that leave these round traces. After the bone/tooth is laid down these guys come along and go to work. 

Image Credit: MegaTeeth

 

We get similar examples from time to time @digit has some great links in this thread discussing them if you are interested.

 

Cheers,

Brett

[caldigger]

Oddly enough, I have collected boxes of bones from Bakersfield and have yet to find one with clam borings.  

[digit]

Yup. I'd say boring clams--really interesting (but boring).

 

Were these to be some sort of tooth marks from something like gators or the like (a common misconception when seeing holy dugong bones from the Peace River here in Florida) I'd expect there to be some sort of mechanical "crushing" damage to the bone surrounding the depression. Given that they are cleanly excavated cavities I'm assuming they are acidically bored pits by something like piddock clams (or similar) on disarticulated bones post mortem and not some sort of feeding damage by a prey species.

 

I too cannot recall ever seeing this reported from Shartooth Hill so that is a very interesting find. I'm wondering if there is any research institution studying material from STH? If this is an unusual find, they may be interested in such a specimen. 

 

Thanks for sharing. Hope the research on this leads to something interesting.

 

 

Cheers.

 

-Ken

[ScottM]

Interesting! I can confirm there seem to be no crushing marks anywhere near the pits. And they are very smooth. If these are indeed something unusual for the site, I'd be happy to talk to someone about it. With the amount of material that's been examined from STH and the fact that I've got 5 of these depressions in just 2 little pieces of bone, I would have to think someone else must have seen these before. Maybe this thread will live long enough to catch someone's eye. Thanks as always for the fast, knowledgeable, and helpful replies.   

[JBMugu]

I have found a few bones with the same indentations. I have found one or two mollusk shells in the fossil layer so I assumed it was mollusk marks. 

[siteseer]

15 hours ago, caldigger said:

Oddly enough, I have collected boxes of bones from Bakersfield and have yet to find one with clam borings.  

 

Right.  I can't remember finding any bone with borings either.  However, I have seen mollusk casts before.  They're very rare.  Bob Ernst found a few across the 70's-2000's.  He gave me one or two so I could have an example - will try to provide a photo.

 

Jess

[siteseer]

2 hours ago, JBMugu said:

I have found a few bones with the same indentations. I have found one or two mollusk shells in the fossil layer so I assumed it was mollusk marks. 

 

Hi JB,

 

Shells would be even rarer than the casts as it appears the chemistry of the sediment was destructive to shell composition.  That's interesting.

 

Jess

[caldigger]

I have found an occasional shell cast. Usually they disintegrate right away due to being made in compacted silt/sand matrix.

[siteseer]

14 minutes ago, caldigger said:

I have found an occasional shell cast. Usually they disintegrate right away due to being made in compacted silt/sand matrix.

 

Yeah, I think Bob consolidated any he found with glyptol right away.  In some spots the rock is more solid but he still hit it with the glyptol.  People don't use that anymore because of the yellow-green haze it leaves even after years and it wasn't really formulated for that anyway..