Danaoceras
Danaoceras is a nautiloid cephalopod from the middle Silurian of central Europe included in the oncoceroid family Polyelasmoceratidae. Similar specimens from the middle Devonian of North America may belong. "Danaoceras" has a laterally compressed shell curved such that the ventral or siphuncular side is longitudinally concave, i.e. is endograstric. The siphuncle, which is ventrally submarginal, contains laminar actinosiphonate deposits. "Danaoceras" is the ancestral genus of the Polyelasmoceratidae and is possibly derived from either "Oonoceras" or "Oocerina" of the Oncoceratidae based on similarities of the siphuncle