Strange trace fossil (?) from Texas

[Bob Clouser]

I found this in Texas, east of San Antonio, near Garden Ridge. It came from Cretaceous strata (Edwards ls., Del Rio clay,  or Buda ls.). The matrix is a soft chalky tan-colored limestone. I think it's a trace fossil. It broke apart on transport/recovery, so I reassembled the sections I could. It also had what looks like a bivalve shell associated with it at one end, and a small 2-cm-long tube-like cast. The main fossil is a long flattened tube(?) or tunnel(?), with a very elliptical cross-section: 15 mm wide, 5 mm thick. It has two narrow ridges that run the length of the fossil on one side. Total length, if you reassembled it all together, is about 28 cm.

 

Thanks for any ideas -- this one I have no idea about. I'm pretty sure it's a trace fossil -- a tunnel, burrow, or filled-in depressed track?

 

Thanks,

Bob

      The whole fossil:

 

 

 

Note the two narrow longitudinal ridges.

  Bivalve(?) shell and small tube

Lengthwise view.

  Shell?

 

 

[ynot]

Looks like a trace fossil to Me, maybe a clam burrow.

How was the shell associated with the "tube"?

[Bob Clouser]

6 minutes ago, ynot said:

Looks like a trace fossil to Me, maybe a clam burrow.

How was the shell associated with the "tube"?

I recall that it was attached at one end of the "burrow".

[ynot]

It would seem that if the clam were whole and actually attached to the burrow it would have been a good association, but as a fragment that is not really attached it is just a coincidence and the burrow is probably an arthropod or some other burrowing invert. other than a clam.

 

4 minutes ago, Bob Clouser said:

I recall that it was attached at one end of the "burrow".

 

[Bob Clouser]

Thanks. I guess I'll id it as a trace fossil, burrow or arthropod or clam.

[abyssunder]

At first glance, they look like some Polychaeta/Serpulimorpha calcium-carbonate tubes, like Hamulus with those lateral "wings". They should be hollow in the middle.

Something like these:

 

I'm sure the assembled fragments are from different specimens.

 

[Guguita2104]

I vote for arthropod trace fossil.

Regards,

[Bob Clouser]

I want to thank everyone for their inputs and comments. I'm calling it an arthropod burrow, trace fossil.