Suvarna Garge (Editor)

Angelinoceras

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Kingdom
  
Class
  
Order
  
Rank
  
Genus

Phylum
  
Mollusca

Subclass
  
Family
  
Similar
  
Lituites, Nautilida, Nautiloid

Angelinoceras is a lituitid 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.

References

Angelinoceras Wikipedia


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