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 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]
