Tentaculitoids are a poorly known group of invertebrates that had a calcium carbonate, conical shell, that is has horizontal ribs. These marine organisms ranged from Ordovician to Devonian and are common in the Columbus and Delaware Limestones of Middle Devonian age. Most specimens are an inch or so in length.
- Bergstrom, S. M., 1996. "Tentaculitoids," in Fossils of Ohio, edited by R. M. Feldmann and Merrianne Hackathorn. Ohio Division of Geological Survey Bulletin 70, p. 282-287.