''Kayoceras'' is a genus of middle Silurian nautiloid cephalopods, known from Iowa and Illinois, belonging to the

Discosoridae Discosoridae comprise a family of endogastric discosorids, (Cephalopoda, Nautiloidea), with endocones in the siphuncle, ranging from the Middle Silurian to Middle Devonian. Shell morphology The shell in the Discosoridae is conical, expanding va ...

. Related genera include ''

Discosorus ''Discosorus'', a genus of the Discosorida and member of the family Discosoridae. Not to be confused with ''Discoceras''. ''Discosorus'' consists of rapidly expanding endogastric brevicones, mostly known from isolated siphuncles composed of broad ...

'', '' Endodiscosorus'', and '' Stokesoceras''. ''Kayoceras'' has a short, breviconic shell, like ''Discosorus'', but with a more central

siphuncle The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and ...

. Derivation is probably from ''Discosorus'', through an evolutionary shifting of the siphuncle position, which has its origin in the

Lowoceratidae The Lowoceratidae is a small family of discosorids, early nautiloid cephalopods, from the Middle Silurian in which the characteristic bullette is found only in early growth stages. Lowoceratids were first found in Southampton Island in the Ca ...

, possibly through '' Tuyloceras''.

References

* Curt Teichert, 1964. Nautiloidea -Discosorida; Treatise on Invertebrate Paleontology, Part K. Geological Society of America and University of Kansas Press.
''Kayoceras''
, Paleobiology database. Prehistoric nautiloid genera Discosorida {{paleo-nautiloidea-stub