A DEVONIAN MICRO-BAGPIPE: A SAC-SHAPED PYRITIZED CTENOSTOME BRYOZOAN FROM THE HAMILTON GROUP (GIVETIAN) OF PENNSYLVANIA

Pyritized specimens preserving the soft-body exterior of a bryozoan occur with a unique small shelly fauna from the Lower Tully Formation. Locations of the stolon, anus and mouth are readily identified on most specimens while a handful also show muscle attachments. The specimens have distinct, long stolons and are preserved as individuals rather than colonial fragments. This suggests that they are ctenostomes. We believe the living organism had a chitinous exterior. An alternative hypothesis would be that these are more conventional bryozoans in which the original calcareous exoskeleton has been lost. The associated fauna includes juvenile bivalve and gastropod shells, abundant dacryoconarids, less common but diverse ostracodes, rare conodonts, and abundant pyritized burrows and "megaspores". As we previously reported, the enigmatic Jinonicella is also found within this bed. This microfauna is limited to a single bed that we consider a lagerstätten. Fossil preservation and the associated fauna and flora suggest a shallow water flotsam within dysaerobic bottom and/or pore water that allowed for the preservation of aragonitic and chitinous organisms through replacement of original hard and soft tissues by iron minerals.