''Cyrtobaltoceras'' is an extinct

cephalopod A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head ...

genus known from the upper Lower Ordovician Fort Cassin Formation at Valcour, N.Y. that is included in the

Nautiloid Nautiloids are a group of marine cephalopods ( Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and ''Allonautilus''. Fossil nautiloids are diverse and speciose, with over 2,500 recorded species ...

family

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, exist ...

Taxonomy

''Cyrtobaltoceras'' was named by Flower (1964 who then assigned it to the Baltoceratidae which at that time was included in the

Ellesmerocerida The Ellesmerocerida is an order of primitive cephalopods belonging to the subclass Nautiloidea with a widespread distribution that lived during the Late Cambrian and Ordovician. Morphology The Ellesmerocerida are characterized by shells that ...

. The Baltoceratidae, along with included genera, has since been moved to the Orthocerida.Kroger et al 2007; Early orthoceratoid cephalopods from the Argentine Precordillera, Journal of Paleontology Nov 2007; v. 81; no. 6; p. 1266-1283;

Morphology

The genotype, ''Cyrobaltoceras gracile'' Flower, is based on a small, slender, incomplete, 25 mm long shell with a slight exogastric curvature. Sutures form lobes across the ventral side but go transversely straight across the dorsum. The siphuncle is proportionally large, almost half the shell diameter in width, and lies against the ventral margin.

Retention

The holotype of ''Cyrtobaltoceras gracile'', Reusseau Flower's no. 341, is housed in the paleontological collection of the New Mexico Museum of Natural History and Science in Albuquerque, N.M (U.S.A)

''References''

* ''Fossils'' (Smithsonian Handbooks) by David Ward {{Taxonbar, from=Q5201012 Prehistoric cephalopod genera Ordovician cephalopods Ordovician cephalopods of North America Molluscs of North America Orthocerida