Amaltheus; Print; Amaltheus is an oxyconic ammonite with a fairly open umbilicus; serrated keel; and slightly sigmoidal ribs from the Lower Jurassic; many of which are strigate. Amaltheus; named by de Montfort; 1808; is indicative of the upper Pliensbachian stage in Europe; north Africa; Caucasus; Siberia; N. Alaska; Canada; Oregon; and possibly Honduras; and is the type for the Amaltheidae and a member of the Eoderoceratoidea.