Eagle Ford Decapoda?

[Titan]

I dug this out of an Eagle Ford group embankment yesterday and wanted to get some thoughts on it. There was a very thin layer containing a few black (phosphate?) pebbles and I dug some out to examine. This one was shaped differently so I took it home to investigate further. As soon as I recognized symmetry I knew I had more than a pebble. I'd love to learn what it might be. 

 

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2: Specimen rotated away from ruler 1/4th turn.

 

3: Specimen rotated away from ruler an additional 1/4th turn.

 

4: Rotated an additional 1/4th turn.

 

Thanks,

 

 

 

 

[Titan]

One of the other pebbles I had in my "To Investigate" pile looks a lot like the above specimen. I've added it here as well just to hopefully aid in identification. I'm thinking maybe a shrimp of some kind.

 

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Edited August 31, 2021 by Titan
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[Plax]

crabby for me. Something like a Hoploparia maybe if they occur in that formation. Just a guess not offering an actual ID. I'd google "Eagle Ford Decapoda"