Fossundecima konecniorum
Pennsylvanian
Francis Creek Shale
Pit 11, Kankakee County
Illinois, USA.

Fossundecima konecniorum is an extinct segmented marine worm belonging to the polychaete group, which includes modern bristle worms. These organisms lived on or within soft sediments in shallow marine to estuarine environments.
64mm polychaete on 64mm paired concretion.