ID help: oyster or not? Modern or fossil?

[MrNLovesRocks]

Hello again! I've got one that is really puzzling me. I went on a walk in city limits of Pittsburg, KS, and on the ground in the middle of the deer trail was a shell. No matrix or anything on it that I could see at first. The deer trail is on top of a rise that has trees and old house sites. The path is constantly showing black shale debris working up from the ground. In my recent experience, dark shale and light colored limestone are the alternating surface layers here. Local rocks and fossils are all Carboniferous or older, unless there are undocumented Cretaceous outcrops that extend from Cherokee county to the south somehow (Kansas Geological Survey publication on my local stratiography.)  

 

My first thoughts were that this is local and dropped here by a predator, as we have lots of water nearby. I ruled this out as: 1) it was still over a mile to the nearest body of water that could support bivalves this size, 2) I've spent a lot of time grabbing bivalves from Kansas water and I've never seen this shell. I've seen lots of mussels and clams but nothing like an oyster (I checked The Great Plains Nature Website guide on bivalves,) this has a golden-Ratio bend to it, is longer than it is wide, and has an oyster shape of the cup and has the landmarks on the edges of the shell. I need help confirming it's an oyster and not a weird clam or something native I don't know.

 

 

 

I thought it also could be a castoff from someone's dinner, since I was in town limits near abandoned house sites. This is Kansas so getting Oysters here would be a relatively decent thing since refrigerated shipping. If it was farmed it probably wouldn't have the parasite marks, am I correct there? Could it be a souvenir from Florida or something?

 

 

(Image 1) Above: back of the shell showing two points that look like attachments or borings of another creature into the shell. The central bore has material fused into the bore.

 

(Image 2, image 3) Below 2: On the right of these images is some material that might be matrix or something else. I haven't been able to tell under my loupe because I don't know what I'm looking for with shell surfaces .

 

(Image 4) Below: hinge of the shell and a small damaged point of the interior showing layers of shell msterial.

 

 

(Image 5) below: muscle scar. Can anyone help me determine if this was cut with a tool? 

 

 

(Image 6) below: close up of bore holes. Centered hole shows light brown remains of something next to the deepest part of the bore

 

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I didn't find a perfectly released fossil oyster shell, right? I'm struggling with finding online identification for modern oysters that don't depend on taste and texture of the flesh. My brief research only indicated oysters from the Cretaceous on but that's probably just for the examples used, right? Any suggestions for how to go about this appreciated as well as actual IDs!  Also open to suggestions of how to take better pictures. I currently only have my smartphone but I have been trying to improve the lighting and getting closer with good focus. Open to input on all of this!

 

Thank you all and have a great day!

[ynot]

Looks like an oyster to me, possibly a discard from a fancy dinner in one of the old houses.

[Rockwood]

I can't tell its age from the shell morphology, but the Cretaceous rock of North Texas is littered with oysters that look similar to this. They may have made it that far north in the seaway at some time. 

[hemipristis]

Oyster yes, probably modern, as the nacre on the inside of the shell remains (near the muscle scar)