Angelinoceras

Angelinoceras Temporal range: M Ordovician
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Nautiloidea
Order:	Tarphycerida
Family:	Lituitidae
Genus:	Angelinoceras Hyatt, 1894

Angelinoceras is a genus of lituitids from the Middle Ordovician that starts off with an open spiral of about 1.5 strongly compressed whorls followed by a straight orthoconic section that continues to expand for a length about equal to the diameter of the coiled portion before retaining a more or less consistent diameter. The juvenile spiral portion has a deep indentation on the ventral side of the aperture for the water-jet funnel, known as a hyponomic sinus, that becomes broad and shallow in the straight-shelled adult portion.

Angelinoceras is most likely derived from Holmiceras by a further opening of the initial spiral and a reduction in the expansion of the orthocone.

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