Activity Chad Bruce posted a new specimen in the group What is it? from the myFOSSIL app 10 months, 1 week ago 10 months, 1 week ago 10 months, 1 week ago Chad Bruce has contributed a new specimen to myFOSSIL! Paul McLain replied 10 months, 1 week ago This could be an internal cast of a Brachiopod. Shell fills with sediment and dissolves away leaving behind a replica of the inside of the critter rather than the outside. These internal casts are called steinkerns.