Sequences of Tremadocian and earliest Arenigian graptolite faunas in North America, Scandinavia, and Taimyr, U.S.S.R., are similar enough to suggest that these regions were coprovincial during that time interval. The most noteworthy difference involves the earliest Tremadocian faunas represented by the Staurograptus fauna in North America (and Australia) and the Dictyonema flabelliforme fauna in Britain, Belgium, North Africa, Scandinavia, Estonia, and Taimyr. The two distributional patterns are known to overlap only in eastern North America.

During middle Arenigian to Llanvirnian time, two faunal provinces became differentiated--a European Province including Britain, western Europe, North Africa, and Scandinavia, and a Pacific Province including North America and Taimyr. Arenigian faunas of the European Province are characterized by diversification of multiramose dichograptid genera, including the endemic Holograptus, Temnograptus, and Trochograptus. Expatriate genera and species from the Pacific Province are known from the more westerly localities of the European Province, and expatriate forms from the European Province are present in eastern North America. Pacific middle Arenigian faunas are characterized by pendent Didymograptus, Goniograptus, and Sigmagraptus, but the late Arenigian genera Cardiograptus, Oncograptus, and Skiagraptus that are so conspicuous in western North America (and Australia) are unknown in the Appalachian geosyncline.

During Llanvirnian time, European Province faunas comprised large pendent species of Didymograptus and cosmopolitan biserial genera. In Scandinavia, expatriate elements from the Pacific Province may be present in Holmograptus, Abrograptus, Pterograptus, and terminal species of Isograptus and Tetragraptus. Pacific Province faunas are characterized by sinograptids (especially in western North America), Loganograptus, Pseudobryograptus, Paraglossograptus, and terminal species of Cardiograptus and Trigonograptus.

After Llanvirnian time, the two provinces lost their separate identities because most of the dichograptid genera in the Pacific Province became extinct, leaving essentially cosmopolitan leptograptid and biserial diplograptid and glossograptid genera.