The Toarcian takes its name from the city of
Thouars, just south of
Saumur in the
Loire Valley of
France. The stage was introduced by French palaeontologist
Alcide d'Orbigny in 1842, after examining
rock strata of this age in a
quarry near Thouars. In Europe this period is represented by the upper part of the
Lias. The base of the Toarcian is defined as the place in the stratigraphic record where the
ammonite genus Eodactylites first appears. A global reference profile (a
GSSP) for the base is
located at
Peniche, Portugal. The top of the stage is at the first appearance of ammonite genus
Leioceras. In the
Tethys domain, the Toarcian contains the following ammonite
biozones: • zone of
Pleydellia aalensis • zone of
Dumortieria pseudoradiosa • zone of
Phlyseogrammoceras dispansum • zone of
Grammoceras thouarcense • zone of
Haugia variabilis • zone of
Hildoceras bifrons • zone of
Harpoceras serpentinum • zone of
Dactylioceras tenuicostatum == References ==