The Jurassic ammonite Pseudolioceras (Tugurites) of the Bering Province
Two species groups can be distinguished in the evolution of Pseudolioceras s.l. The first ranges through most of the Toarcian (and? earliest Aalenian) and makes up the circum-Boreal Pseudolioceras s.s. The second extends through the Aalenian and earliest Bajocian of the Bering Province and constitutes the subgenus Tugurites, of considerable chronostratigraphic importance.