Can you help me identify these fossils from the devil’s river area in Texas?

[SolFire]

My grandparents own land on the Devil’s River in west Texas and I’ve been hunting fossils with them there since I was six years old. When I was younger I thought that these might be fossilized dinosaur bones, but I doubt that now. My grandparents think that they’re plants  but I also doubt that. I’ve been thinking maybe they’re some sort of tube worm, or a coral, but I have a feeling that they’re something I don’t know of at all. So, I figured it would be good to ask here with hope that someone will know more than we do.  I read this morning that the devil’s river limestone is Cretaceous. 

 

The fossil in the bottom left of this picture is a nice cross section of what I’m interested in. The distinct segments or chambers remind me of the structure of an ammonite or a nautilus, which made me wonder if they could be a shelled cephalopod.

 

They seem to be hollow (at least some of them):

 

I found this piece today and was happy to see such a nice cross-section of the intricate wall structure:

Edited March 17, 2020 by SolFire

[Creek - Don]

 It resembles petrified tree trunk with bark.   I also see some white crystal mineral on the second image that are associated with petrified trees or plants. That area is Salmon Peak Limestone (early Cretaceous).  You and your grandparents found petrified Cretaceous tree. Very nicely preserved.  

 

[SolFire]

14 minutes ago, Creek - Don said:

 It resembles petrified tree trunk with bark.   I also see some white crystal mineral on the second image that are associated with petrified trees or plants. That area is Salmon Peak Limestone (early Cretaceous).  You and your grandfather found petrified Cretaceous tree. Very nicely preserved.  

 

We find them in the same rocks as many different types of shells, could they be plants that grew in the ocean? Most of the shell fossils we find have crystals within them. 

Edited March 17, 2020 by SolFire

[Creek - Don]

15 minutes ago, SolFire said:

We find them in the same rocks as many different types of shells, could they be plants that grew in the ocean? Most of the shell fossils we find have crystals within them. 

Probably resembles more like this Cretaceous environment

 

[Uncle Siphuncle]

Could these be rudists?

[JohnJ]

23 minutes ago, Uncle Siphuncle said:

Could these be rudists?

 

I agree.  These are rudists.

[Quer]

I agree with rudists, too.

 

Elevator-type rudists can form successive chambers:

 

[SolFire]

8 hours ago, Uncle Siphuncle said:

Could these be rudists?

I think so! I just found these pictures detailing the structure of the rudist shell. They even use the same terminology to describe it.

Edited March 17, 2020 by SolFire

[SolFire]

3 hours ago, Quer said:

I agree with rudists, too.

 

Elevator-type rudists can form successive chambers:

 

This makes me even more sure! Thanks for the photo!

[Ludwigia]

Yup. I was seeing rudists as well.