Crab carapace? Central Texas Cretaceous

[JamieLynn]

hello all!! I found what I thought was just the end of a bivalve, but it has these odd bumps which I associate with crab fossils. (Not having found anything but a couple of partial claws, I am just guessing here). It was found in Blanco County in Central Texas,  Glen Rose formation, I think. (second picture, couldn't get them in the right order. Sorry)

 

The first picture is another find from that same place, the regular lines of dots intrigued me. Any info would be much appreciated!! 

 

[ynot]

Looks crabby to Me, but I do not know crabs so good.

[FossilDAWG]

The first specimen shows holes made by some boring (as in drilling into the substrate) organism, possibly a sponge.  The second may be a partial crab carapace, but it would help to see views from other angles.

 

Don

[JamieLynn]

[JohnJ]

I agree with Don on the first piece.  The second has all the indicators of being a clam steinkern.  Crab bits in the Glen Rose Formation usually present as white or creamy white and are clearly a separate layer from any matrix.

[jpc]

nice bonus blue-green coloration on this one.  I also see a crab.

 

[JamieLynn]

I definitely thought it was clam at first too, but am just thrown by the bumps on it. Never seen those on a clam before. I have many many clams from that area (deerhearts) and none have looked like this. 

[JohnJ]

If it was a crab carapace, it would have bits of a distinctly separate layer from the encasing matrix.  Bumps like that can occur due the differential erosion caused by ground water or rain...harder bits in the rock stand out when softer parts around them are washed away.

[Rayminazzi]

@Uncle Siphuncle