Help id’ing a fossil

[aboyd03]

Hey all!  Looking for assistance Identifying this fossil.  Found in west Texas, Brewster county.  
 

Appreciate any suggestions!

[Creek - Don]

What part of the Brewster County did you find this?  You can use this map https://txpub.usgs.gov/txgeology/.  There are several formations in that area.  There are some Cretaceous formation in that area contains rudists.  Looks and shapes like interior of rudists bivalve.  

Edited September 6, 2022 by Creek - Don

[aboyd03]

Thanks Don.  Location is just off hwy 170 between terlingua and Lajitas (about halfway between the two). 

[Creek - Don]

19 minutes ago, aboyd03 said:

Thanks Don.  Location is just off hwy 170 between terlingua and Lajitas (about halfway between the two). 

Area is a late Cretaceous Pen and Bouquilas formation.  Common to find marine mega fossils in the area.  I belive you found piece of rudists bivalve.  

[abyssunder]

It looks like a rudist lower valve in longitudinal section (in the last picture).