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.
| Forresteria Temporal range:
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| Fossil of Forresteria species. Coniacian of Madagascar | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | †Ammonoidea |
| Order: | †Ammonitida |
| Family: | †Collignoniceratidae |
| Subfamily: | †Barroisiceratinae |
| Genus: | †Forresteria Reeside, 1932 |
| Species | |
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See text | |
Description
editAlthough 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
editspecies 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]
References
edit- ^ a b Cobban, William A. et al (2006) "A USGS Zonal Table for the Upper Cretaceous Middle Cenomanian-Maastrichtian of the Western Interior of the United States Based on Ammonites, Inoceramids, and Radiometric Ages" [1] USGS (Open-File Report 2006–1250)
- ^ W.J Arkell et al., 1957 Mesozoic Ammonidea. Treatise on Invertebrate Paleontology, Part L Ammonoidea.
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