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Post Oak Creek - Oyster with Anomoly

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facehugger

So I went to north Texas a few weeks back. Stopped by NSR and Post Oak Creek in Sherman. Both were pretty flooded still, which hampered my efforts. Had a very meagre haul, which was disappointing. 

 

Back in Houston, about a week later, I was going over my disappointing finds, after a good washing. That's when I noticed an oyster I picked up in Sherman had a rather unusual anomaly. It was odd that I even picked it up - I already have several nice oysters of this variety from the same location. I try not to take home too many duplicates, usually leave them for the next guy. 

 

Well, this was a surprise. And I would say made the whole trip worth it. Oyster and Sherman experts, tell me your thoughts. 

 

The anomaly appears spherical in shape, entirely back material, high gloss. I do not want to prep the object or to try to remove, as I feel it adds incredible charm to a rather ordinary fossil. 

 

Sherman, Texas. Eagle Ford Formation, Cretaceous. 20181109_113056.thumb.jpg.1bfa113b9df0db61c22f328ca1c0a5ad.jpg20181109_113142.thumb.jpg.8be40b8679cae6c2ff665f83dc1e15b9.jpg20181106_185826.thumb.jpg.6376fb1d6ba045992ca28d8df94dcff4.jpg

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Misha

Oysters are sometimes found with pearls in the fossil, but here it seems a bit too glossy and the fossil usually have a uniform color including the pearl. 

Is it completely spherical or more like a drop of liquid in shape?

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DPS Ammonite

It looks phosphatic. Might be a pycnodont fish tooth.  link.  

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fossilnut
2 minutes ago, Misha said:

Oysters are sometimes found with pearls in the fossil

The main word here is "in". This object is out-but in a covering matrix so  possibly a pearl from another shell? I'm not saying it is a pearl, can't tell from what I can see. But it is very interesting. Are pearls found in this Cretaceous formation?

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Misha
2 minutes ago, fossilnut said:

The main word here is "in".

I can't really tell from the picture what position the thing is in, it would be hard to get a good shot of something like that.

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Misha
8 minutes ago, DPS Ammonite said:

Might be a pycnodont fish tooth

Do they ever come so small and so round?

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DPS Ammonite

Pearls occur nearby in the Kamp Ranch Limestone which are thought to be Inoceramid. 

 

The black tooth appears to be in the matrix that is stuck to the outside of the oyster.

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facehugger
35 minutes ago, Misha said:

Oysters are sometimes found with pearls in the fossil, but here it seems a bit too glossy and the fossil usually have a uniform color including the pearl. 

Is it completely spherical or more like a drop of liquid in shape?

It's hard to tell, since about 1/3 of it is obscured where cemented to the oyster. But the top portion gives a spherical impression...

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facehugger
24 minutes ago, DPS Ammonite said:

Pearls occur nearby in the Kamp Ranch Limestone which are thought to be Inoceramid. 

 

The black tooth appears to be in the matrix that is stuck to the outside of the oyster.

 

28 minutes ago, Misha said:

I can't really tell from the picture what position the thing is in, it would be hard to get a good shot of something like that.

The anomaly is occurring on the concave side of the oyster. 

 

Hmmm. Interesting info. Tell you what. When I get home, I will try to get some even closer shots, at different angles.

 

Thanks for the input guys! Pearl was immediately a consideration, due to the positioning. Didn't consider a small tooth. 

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DPS Ammonite

Try putting acid on it. A pearl should fizz; a tooth should not.

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DPS Ammonite
12 minutes ago, facehugger said:

 

The anomaly is occurring on the concave side of the oyster.

The concave side is the exterior of the upper shell of the oyster. Both shells are present in the oyster. Note the pronounced ribs. The interiors of the oyster are much smoother.

See this paper on the  Cameleolopha bellaplicata oyster: link

 

https://www.researchgate.net/publication/287588150_The_Late_Cretaceous_oyster_Cameleolopha_bellaplicata_Shumard_1860_guide_fossil_to_middle_Turonian_strata_in_New_Mexico

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facehugger
32 minutes ago, DPS Ammonite said:

Try putting acid on it. A pearl should fizz; a tooth should not.

That is worth a shot. Though I loathe to damage it, regardless of identification. Household acids? Lemon juice? Vinegar?

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DPS Ammonite
1 hour ago, facehugger said:

That is worth a shot. Though I loathe to damage it, regardless of identification. Household acids? Lemon juice? Vinegar?

Try vinegar first then dulute HCl. Rinse well in water.

 

All the north Texas pearls that I have seen have had a dull finish. The argonitic coating long since has dissolved. The pycnodont teeth are usually very glossy like yours.

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facehugger
55 minutes ago, DPS Ammonite said:

 

 

All the north Texas pearls that I have seen have had a dull finish. The argonitic coating long since has dissolved. The pycnodont teeth are usually very glossy like yours.

Would oysters have been on the pycnodonts menu? If so, then the chance of it being a tooth seems even more likely...not as exciting as a pearl, but still pretty unique, especially attached to the shell...will still try the vinegar soon and report results.

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fossilnut
1 hour ago, DPS Ammonite said:

pearls that I have seen have had a dull finish.

Yep they aren't "pretty" but are pretty rare and a great find. This one is a beach find from NMB, SC. I believe it is fossil not recent. Blister pearl attached to a Quahog-Mercenaria shell. About the size of a US quarter. Have also found Miocene Calvert Cliffs blister pearls attached to Panopea -geoduck shells. All of these are a creamy brown color, porcelain looking without any luster from aragonite covering (mother-of-pearl) as noted by @DPS Ammonite

DSCN4959 (4).JPG

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DPS Ammonite
1 hour ago, facehugger said:

Would oysters have been on the pycnodonts menu? If so, then the chance of it being a tooth seems even more likely...not as exciting as a pearl, but still pretty unique, especially attached to the shell...will still try the vinegar soon and report results.

Based on the size of the teeth, I doubt that they ate the oyster that you have. Maybe a ptychodus shark ate them. 

 

Teeth of all sorts especially sharks are very common associated with the rock that the oysters are in. 

 

Keep your eye out for branching bryozoa and golf ball sized coral colonies that grew on the oysters. Both are unnamed and unstudied. I suggested a coral species as a possible ID in an old TFF post.

 

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facehugger
On ‎11‎/‎9‎/‎2018 at 2:45 PM, DPS Ammonite said:

Try vinegar first then dulute HCl. Rinse well in water.

 

All the north Texas pearls that I have seen have had a dull finish. The argonitic coating long since has dissolved. The pycnodont teeth are usually very glossy like yours.

Update. While the surrounding matrix material exhibited some fizzing, the anomaly did not. 

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DPS Ammonite
1 minute ago, facehugger said:

Update. While the surrounding matrix material exhibited some fizzing, the anomaly did not. 

A pycnodont tooth and not a pearl is your best bet.

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