The Baltic nautiloids Cyrtoceras ellipticum Lossen 1860, C.priscum Eichwald 1861, and Orthoceras damesi Krause 1877

The type specimens of Cyrtoceras ellipticum Lossen 1860 and proposedly conspecific material from Baltic erratic boulders of late Llanvirn (Lasnamägian) age are closely similar to Phthanoncoceras oelandense Evans & King 1990 from the latest Arenig (early Kundan) of Sweden. Cyrtoceras priscum Eichwald 1861, co-occurring with C. ellipticum, is generically distinct in its short living chamber and much more advanced siphuncular structure; it probably represents Oonoceras lineage. The type of Orthoceras damesi Krause 1877 from the Baltic Beyrichienkalk erratic boulders, which is smooth, except for faint growth lines, appears to represent a later ontogenetic stage in development of a kionoceratid with prominent longitudinal riblets and annulations at early stages. It is probably a derivative of the main longiconic lineage of Spyroceras, in which prominent conch ornamentation disappeared in adult specimens