Dallas creek Rudists fossil?

[Creek - Don]

I found this long cylinder sticking out of the creek wall few weeks ago.  I had no choice , but to break it from the rock.  Ended up in several pieces. 

I'm not quiet sure 100 percent what this is.  I searched the forum, but can't figure out other than Rudist.

 

 

[DPS Ammonite]

Take some clear, up close photos of the ends of some of the pieces. We are looking for sub mm cellular textures typical of rudists.

 

What is it made of calcite or silica? Scratch it with a steel knife blade: does it scratch? Does it fizz in acid?

[Creek - Don]

Hello.   Here is some close up picture of the end. These are limestone (Austin chalk).   

 

[Creek - Don]

I figured out what this could be! According to the Geology of Dallas county book,  this could possibly be a Upogebia rhacheochir, rare fossilized cretaceous crustacean which resembles prehistoric

lobster.  Can't find any other information about this creature on the Internet other than source from this book. 

  

[JohnJ]

This is definitely not a crustacean.  If it were, there would be evidence of the carapace or shell.  It might be a burrow cast.

[Shamalama]

I vote for a burrow cast though the texture along the sides feel like a Rudist. However, I thought those generally were found in reef like complexes and so you would find other long examples like this one very close by.