The identity of the Ordovician (Darriwillian) graptolite Fucoides dentatus Brogniart, 1828

The biostratigraphically important Middle Ordovician (Darriwilian) biserial graptolite Fucoides dentatus Brongniart, 1828 is redescribed and illustrated from its type material and from additional specimens collected at the type locality – Levis, Quebec, Canada. It is referred to Levisograptus gen. nov., which includes also the austrodentatus group ofearly axonophoran graptolites. The species has previously been confused with a younger, mid-Darriwilian species, now referred to as Eoglyptograptus gerhardi sp. nov., and recognized as the type species of the genus Eoglyptograptus Mitchell. Both species can be differentiated easily by their respective proximal developmen types and show nonoverlapping biostratigraphical ranges. Levisograptus dentatus (Brongniart) is an important biostratigraphical index species in the early Darriwilian. Eoglyptograptus species are found in the higher Darriwilian and are biogeographically restricted to the Atlantic Faunal Realm.