Fauna???? ID request

[Ruger9a]

Good morning forum.  Can anyone tell me if this fossil is fauna or ?????  It's from the early Triassic, lower Muschelkalk, Libiaz, Poland. Matrix is 70 x 50cm

[Plax]

If there's a clam steinkern inside the fat end I'd say it was gastrochaenolites? May have it misspelt. Basically a mollusk tube burrow or dwelling. Could be very wrong here though as I have no experience with this area or age.

 

[Ruger9a]

Thank You Plax!!!!  You're right on the money.  This is what I found based on the information you provided  -  Gastrochaenolites is a trace fossil formed as a clavate (club-shaped) boring in a hard substrate such as a shell, rock or carbonate hardground. The aperture of the boring is narrower than the main chamber and may be circular, oval, or dumb-bell shaped (Kelly and Bromley, 1984). Gastrochaenolites is most commonly attributed to bioeroding bivalves such as Lithophaga and Gastrochaena

 

Lithophaga seems to be the culprit as it's a "stone eating" bivalve.