Angelinoceras
Extinct genus of molluscs
From Wikipedia, the free encyclopedia
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 Temporal range: M Ordovician | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | Nautiloidea |
| Order: | †Tarphycerida |
| Family: | †Lituitidae |
| Genus: | †Angelinoceras Hyatt, 1894 |
Angelinoceras is most likely derived from Holmiceras by a further opening of the initial spiral and a reduction in the expansion of the orthocone.