Endocerida

Endocerida is an extinct nautiloid order, a group of cephalopods from the Lower Paleozoic with cone-like deposits in its siphuncle.

Endocerida comprises a diverse group of cephalopods that lived from the Early Ordovician possibly to the Late Silurian . Their shells varied in form. Some were straight (orthoconic) others curved (cyrtoconic); some were long (longiconic), others short (breviconic). Some long-shelled forms like Endoceras attained lengths as much as 3.5 metres (11 ft). The related Cameroceras is anecdotally reported to have reached lengths approaching 9 metres (30 ft), but these claims are not unproblematic (Teichert and Kümmel 1960). The overwhelming majority of endocerids and nautiloids in general are much smaller, usually less than a meter long fully grown.