Actinoceras - Related Genera

Related Genera

The following actinoceratid genera are closely related to Actinoceras although differing in various details.

Kochoceras, named by Troedsson, 1926, is a middle to upper Ordovician actinocerid similar overall to Actinoceras but with the shell flattened on the venter and with the siphuncle in broad contact with the ventral margin. Kochoceras was first discovered in northern Greenland, which during the Ordovician was near equatorial.

Leurothoceras, named by Foeste, 1921, is an actincerid with a flattened shell and narrower siphincle than in Actinoceras. Siphuncel segments in this genus tend to become strongly elongated in the mature part of the phragmocone.

Paractinoceras, named by Hyatt, in Zittel 1900, is a long, straight, slender-shelled actinocerid with the siphuncle segments in the early stage expanded as in Actinoceras, but becoming narrow in the later stages as in Ormoceras. Paractinoceras has been found in North America in Manitoba, and in Russia in Siberia.

Saffordoceras, named by Foeste and Teichert in 1930, is an actinicerid with a ventrally flattened shell, subventral siphuncle with short segments, and sutures with broad shallow ventral lobes and narrower lateral saddles. Saffordoceras comes from the Middle Ordovician of eastern North America.

Troostoceras, also named by Foeste & Teichert in 1930, is similar to Actinoceras but with a slightly cyroconic and endogastric shell. It is known from the Middle Ordovician of eastern North America and Siberia.

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