Early Devonian fishes from coastal De Long Strait, central Chukotka, Arctic Russia

Abstract

ABSTRACT Calcareous and sandy deposits from the basal members of the Enmakaj and Pil'hikaj formations in coastal exposures along the De Long Strait in central Chukotka, Arctic far-eastern Russia, have yielded two assemblages of fossil fish comprising heterostracan plate fragments, turiniid and other thelodont scales, acanthodian scales and a partial tooth, typical of the Old Red Sandstone facies. Exceptional are acanthothoracid placoderm platelets characteristic of marine facies. In addition a sarcopterygian fragment have been found in Member 1 of the Enmakaj Formation. Some scale surfaces show an unusual, scoured preservation. A Lochkovian age, and most probably basal Lochkovian, is supported for the Enmakaj assemblage, and a somewhat later Lochkovian age is supposed for the Pil'hikaj assemblage. The palaeobiogeographic affinities of these assemblages based on the heterostracans and thelodonts are with other Lochkovian occurrences in Arctic regions such as Severnaya Zemlya, Spitsbergen and the northern a...