Tentaculites oswegoensis is a small animal of unresolved phylogenetic affinities that has often been classified with molluscs or even with marine worms and has recently been interpreted as a lophophorate based on shell microstructure.

Tentaculites oswegoensis was named by 1877 and is known from the Upper Ordovician rocks of the Maquoketa Group.

At KRSP it appears in the basal Silurian of the Kankakee Formation but has not been found in the underlying Ordovician rocks.

In Oswego, Illinois it is found mostly in clusters at Waubonsie Creek in the basal Brainard Formation (Upper Ordovician), just west of the railroad tracks.

The entirety of Class Tentaculita became extinct at the end of the Devonian, leaving no known extant descendants or related species.