The Givetian vertebrate fauna from the Fiskekløfta Member (Mimerdalen Subgroup), Svalbard. Part I. Stratigraphic and faunal review. Part II. Acanthodii

Two body fossils of the Middle Devonian acanthodian Cheiracanthus intricatus Valiukevi?ius have been collected from the Fiskekløfta Member, the upper member of the Tordalen Formation in the Mimerdalen Subgroup of Spitsbergen. One of the specimens is articulated, the first such known of this species. In the Baltic region the species is only known from scales, from the upper part of the Eifelian and the Givetian (Narva to Burtnieki regional stages). Previous workers investigating the Mimerdalen strata speculated that Givetian spores found in the Fiskekløfta Member have been reworked from older deposits, and have given the member a Frasnian age. However, the reworking of an articulated acanthodian from older deposits is a near impossibility, so we are confident in dating the Fiskekløfta Member as Middle rather than Late Devonian. Furthermore, other genera identified from this member include the sarcopterygians Laccognathus Gross, 1941 and Miguashaia Schultze, 1973 and the arthrodire Plourdosteus Ørvig, 1951, also supporting an upper Givetian age, and confirming recent dating based on analysis of the spores. Overall, the fish fauna indicates that the Fiskekløfta Member is most likely contemporary to the Gauja Regional Stage in the Baltic region.

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