Expert urgently needed! Found a very intriguing fossil by the river in Puerto Rico

[abyssunder]

They are rudist fragments.

 

[GallinaPinta]

11 hours ago, Troodon said:

Where was it found

 

That page didn't want to load for me so thanks for uploading that image

I circled the area and added a blue dot where the location of the river is most likely at. 

[GallinaPinta]

7 hours ago, abyssunder said:

They are rudist fragments.

 

Wow. That's amazing, I'm gonna download that pic. Thank you!

[GallinaPinta]

7 hours ago, Rockwood said:

Just curious. Why the urgency ? 

I'm a newbie so I was really, really curious I was going nuts to know the kind of fossil I found so close to my home. 

[FranzBernhard]

23 hours ago, GallinaPinta said:

 

This one does indeed look like a rudist!

But I am still not convinced by the other ones.

Her location seems to be in Caenozoicic strata, but that does not mean very much (transported boulders?)

 

Maybe this paper could help:

https://pubs.usgs.gov/bul/1274g/report.pdf

The Aguada limestone of Northwestern Puerto Rico

"In northwestern Puerto Rico, the upper 85 m contains many thick lenses or beds of very pale orange to bright- yellow, slightly ferruginous chalk containing many beds of large oysters (Ostrea haitensis Gabb) and other fossils."

Franz Bernhard

 

[FranzBernhard]

Btw, here is an example of a fragment of two intergrown lower/left valves of Crassostrea gryphoides from the miocene of Austria, just for comparision. A small oyster is sitting between the two large fragments. Hight of specimen ca. 15 cm, left inside, right outside of the same specimen.

Franz Bernhard

[Rockwood]

8 hours ago, GallinaPinta said:

I'm a newbie so I was really, really curious I was going nuts to know the kind of fossil I found so close to my home. 

Hope you have plenty of shelves and draws. This is how it starts you know. 

[Al Dente]

I see at least two oyster hinges. Here is a similar one from the Oligocene of North Carolina.

[abyssunder]

Franz, Eric, you might be right. If the geological time is in Cenozoic they can't be rudists.
These kind of bivalves (oysters, rudists) sometimes can be very tricky.

[FranzBernhard]

Sure, and they are also closely related.

But what really is the "thing" with the hole in the middle??

Hoping for more photographs from GallinaPinta...

Franz Bernhard

[fifbrindacier]

I also, hesitate between rudist or oyster.

Here is a crassostrea longirostra from the Serravallian and an imprint of Ichthyosarcolites from the cenomanian.

[Rockwood]

2 hours ago, FranzBernhard said:

Sure, and they are also closely related.

But what really is the "thing" with the hole in the middle??

Hoping for more photographs from GallinaPinta...

Franz Bernhard

The holes look like the work of yet another bivalve, loosely referred to as boring clams.

[Bobby Rico]

11 minutes ago, Rockwood said:

The holes look like the work of yet another bivalve, loosely referred to as boring clams.

In the UK we call this type of bivalves Piddocks.

 

nice find btw 

[Rockwood]

2 minutes ago, Bobby Rico said:

In the UK we call this type of bivalves Piddocks.

 

nice find btw 

I suspect they've been called worse.

Shipworms being the subject. 

[abyssunder]

I think, the best match for this one might be a lower valve of Ostrea cahobasensis Pilsbry and Brown , variety portoricana n. var.; new name - Striostrea cahobasensis .

 

[Boesse]

@Al Dente beat me to it - it falls within the range of variation of giant oysters like Crassostrea.

[abyssunder]

The sediments from the mentioned region of Puerto Rico are too young for for rudists.
I can see similar holes like in the specimens in question in the comparative picture below, so it makes sense.