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Forresteria

Genus of molluscs (fossil) From Wikipedia, the free encyclopedia

Forresteria
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Forresteria is an extinct genus of cephalopod belonging to the subclass Ammonoidea. They flourished during the late Turonian and early Santonian of the Late Cretaceous,[1] and were global in extent. Forresteria alluaudi and Forresteria hobsoni are considered marker fossils for the lower Coniacian in the American West.

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Description

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Although the whorl section and ornament of Forresteria are variable, it is easily distinguished from Barroisiceras by the presence of mid-lateral tubercles on the inner whorls, which later disappear or fuse with either umbilical or ventrolateral tubercles. Four subgenera are recognized [2]

  • F. (Forresteria): Whorl section moderately to very inflated. Mid-lateral tubercles fuse with ventrolateral.
  • F. (Reesideoceras): Whorl section less inflated than with F. (Forresteria). Mid-lateral tubercles fuse with the umbilical. Keel disappears on outer whorl leaving venter flat or concave, bordered by ventrolateral clavi.
  • F. (Harleites): Shell compressed, with high keel and steep umbilical wall. Early whorls have weak umbilical, strong mid-lateral, and fine, feeble ventrolateral tubercles.
  • F. (Zumpangoceras): Inclusion doubtful. Known only from crushed specimens from Mexico. Mid lateral tubercle strengthens with age.

Species

species in Forresteria include:

  • Forresteria alluaudi (Boule, Lemoine and Thévenin, 1907)
  • Forresteria brancoi
  • Forresteria hobsoni
  • Forresteria neo-mexica
  • Forresteria petrocoriensis (Coquand, 1859)
  • Forresteria peruana
  • Forresteria seidli (Summesberger H. and Kennedy W.J., Vienna, May 2022 "New results from the Coniacian and Santonian of the Gosau group" (Austria, Abh. Geol. B.A. Band 75, S. 5-13))

Forresteria was named for Robert Forrester of Salt Lake City, Utah.[1]

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References

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