Kayoceras

Kayoceras is a genus of middle Silurian nautiloid cephalopods, known from Iowa and Illinois, belonging to the Discosoridae. Related genera include Discosorus, Endodiscosorus, and Stokesoceras. Kayoceras has a short, breviconic shell, like Discosorus, but with a more central siphuncle. Derivation is probably from Discosorus, through an evolutionary shifting of the siphuncle position, which has its origin in the Lowoceratidae, possibly through Tuyloceras.