Baltoceras is a member of the Ellesmerocerida

Ellesmerocerida

The Ellesmerocerida is a order of primitive cephalopods belonging to the subclass Nautiloidea with a widespread distribution that lived during the Late Cambrian and Ordovician.-Morphology:...

, included in the family, Baltoceratidae

Baltoceratidae

Baltoceratidae is an extinct family of orthoconic cephalopods belonging to the subclass Nautiloidea endemic to what would be Asia, Australia, Europe, North America, and South America during the Ordovician living from about 480–460 mya, existing for approximately .-Taxonomy:Baltoceratidae was...

. The shell of Baltoceras is slender with a subcircular cross section, straight transverse sutures, and a large siphuncle in contact with the venter. Septal necks are short but not vestigial;connecting rings are thick; endosiphonal organic deposits are unknown.

Baltoceras ranges in age from Whiterock to Chazy (Middle Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

.) . The few species known are from the upper Pogonip Limestone of Nevada, the Day Point Limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

 of New York, and the “Orthoceras limestone” of the Baltic region of Europe.

Baltoceras differs from Rioceras

Rioceras

Rioceras is an extinct orthocerid cephalapod genus of the family Baltoceratidae that lived in what would be North America during the Early Ordovician from 480—472 mya, existing for approximately 8 million years.-Taxonomy:...

in the same family in that Baltoceras has deeper camerae, longer septal necks and thinner connecting rings. Also Rioceras is earlier, mostly late Canadian

Canadian Epoch

The Canadian is the Lower or Early Ordovician in North America. The term is common in the older literature and has been well understood for more than a century...

 in age.

Don’t confuse with the orthocerid

Orthocerida

Orthocerida is an order of extinct nautiloid cephalopods also known as the Michelinocerda that lived from the Early Ordovician possibly to the Late Triassic . A fossil found in the Caucasus suggests they may even have survived until the Early Cretaceous...

, Balticoceras