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.
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]