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ammonoid

NOUN
  1. one of the coiled chambered fossil shells of extinct mollusks

How To Use ammonoid In A Sentence

  • Other molluscs are present but less common, including bivalves, scaphopods, orthoconic cephalopods, tentaculitids, and small, indeterminate juvenile ammonoids.
  • Outwardly indistinguishable from other ammonoids, clymeniids are distinguished internally by their dorsal siphuncle, contrasted to a ventral siphuncle in almost all other ammonoids.
  • In summary, clymeniids fell well within the general range of Paleozoic ammonoid geometries, though most members of the Clymeniida tended toward an openly coiled shell with a low expansion rate.
  • This kind of musculature was probably already developed in the cochleate ammonoids.
  • According to these studies, allometric growth is particularly common in Carboniferous and Permian ammonoids.
  • The Triassic ammonoids represent the phylogenetic bridge between Paleozoic and Jurassic ammonoids.
  • Other mature modifications, such as change in the shape of the peristome, are also inconsistently observed in Paleozoic ammonoids.
  • Ammonoids reflected changing environmental conditions by changing their fecundity, whereas in nautiloids a strong heritable differential occurred between genotypes.
  • In these periods, the ammonoids became extremely diverse, but comparatively little is known about their Early and Middle Viséan ancestry.
  • The sediments are noted for their rich ammonoid faunas, which allow detailed biostratigraphic subdivision and correlation.
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