Strange Steinkern

[Misha]

This is a steinkern of a fossil clam that I had purchased, the shell itself fell apart almost immediately and this was left.

I just want to confirm that the things on the surface of it are some kinds of trace burrows from worms,

I am not really sure but that is what they look like to me.

Thank you all.

[Tidgy's Dad]

The worm tubes appear to me to be more recent than the steinkern as they are growing on the mold and not the shell. 

Serpulid worm tubes, i think. 

[DPS Ammonite]

6 minutes ago, Tidgy's Dad said:

The worm tubes appear to me to be more recent than the steinkern as they are growing on the mold and not the shell. 

Serpulid worm tubes, i think. 

If the worm tubes were recent and growing on the interior mold of the shell, then you probably would be looking at their exterior. I think that you are looking at the interior of the worm tubes since they were growing in the interior of a fossil shell that the poster said existed when bought but subsequently fell apart. The worm tubes are slightly younger than the shell which was then buried.

[Rockwood]

6 hours ago, Misha said:

trace burrows from worms,

I agree these are body fossils of worm tubes as DPS Ammonite says.

The loss of the shell was fortunate in a way.

[Al Dente]

Here are some similar worm tubes in an Eocene steinkern from the Castle Hayne Formation.