Hemicosmorthoceras

Hemicosmorthoceras Temporal range: Ordovician-Devonian
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Orthoceratoidea
Order:	Orthocerida
Genus:	Hemicosmorthoceras Foerste (1925)

Geisonocerina is an extinct genus of actively mobile carnivorous cephalopod, essentially a Nautiloid, that lived in what would be present day Europe during the Silurian to Devonian from 422.9—412.3 mya, existing for approximately 10.6 million years.

Hemicosmorthoceras was named by Foerste (1925). It was assigned to Orthocerida by Teichert et al. (1964); and to Endocerida by Sepkoski (2002).

The shell is usually long, and may be straight ("orthoconic") or gently curved. In life, these animals may have been similar to the modern squid, except for the long shell.

Fossil distribution is exclusive to Sardinia, Austrian Alps.

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