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 lituitid from the Middle Ordovician that starts off with an open spiral of about 1.5 strongly compressed whorls followed by an 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.
References
- Flower, R. H. 1950. A Classification of the Nautiloidia. Jour Paleontology, V.24, N.5, pp 604–616, Sept.
- Furnish & Glenister, 1964. Nautiloidea -Tarphycerida. Treatise on Invertebrate Paleontology Part K, Mollusca 3 ...Nautiloidea
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