Contribution to the correlation of the Emsian (Lower Devonian) on the basis of placoderm fishes

Changes in the content of the fish fauna at the Emsian-Eifelian boundary are exemplified by the Severnaya Zemlya section. A global review of the occurrences of Wijdeaspis and its associated placoderms, particularly buchanosteids (Buchanosteus, Luetkeichthys, etc.), early homostiids (Antineosteus, Homostius arcticus), heterostiids (Tollichthys, Herasmius), and Sedowichthys is given. In some sequences (Severnaya Zemlya, Taimyr, Morocco, N.S.W. Australia) the Emsian age of these fishes has been dated by conodonts. The Wijdeaspis arctica Beds of Taimyr, the lower member of the Manturovskaya Formation of NW of Siberian Platform, and the Grey Hoek Formation of Spitsbergen, containing the same placoderms, are thus considered of Emsian age. The Rēzekne Regional Stage of the East Baltic region is also equivalent to the Emsian. Correlation of the Emsian of several areas is presented on the basis of placoderms and some other fish occurrences.