Devonian acanthodians from Severnaya Zemlya Archipelago (Russia)

Acanthodians from the stratigraphic interval of late Pridoli (Late Silurian) to Givetian (Middle Devonian) are studied. Based on 48 acanthodian taxa, biostratigraphic zones are established within the late Pridoli (Poracanthodes punctatus Zone, Krasnaya Bukhta Formation) and Lochkovian (Nostolepis minima Zone), the latter divided into two subzones: Poracanthodes menneri (Severnaya Zemlya Formation) and Diplacanthus poltnigi n. sp. (Pod"emnaya Formation). Two more biostratigraphic units are characterised by index species, but they have no acanthodian-based boundaries (separated by intervals without effective acanthodian characteristics). These are beds with Watsonacanthus costatus n. sp. typical for the Emsian Rusanov and lower Al'banov formations, and Eifelian? or Eifelian/Givetian? beds with Diplacanthus solidus n. sp. (Vstrechnaya Formation). Five new genera and 14 new species are described. They are based on articulated specimens from the topmost Severnaya Zemlya Formation (Acritolepis ushakovi n. gen., n. sp., A. urvantsevi n. gen., n. sp., Acanthacanthus ornatus n. gen., n. sp., Nostolepis decora n. sp., N. fragilis n. sp., Acanthopora transitans n. gen., n. sp. and Acanthospina irregulare n. gen., n. sp.) or on isolated scales identified from different formations (Nostolepis timanica n. sp., N. watsoni n. sp., Watsonacanthus costatus n. sp., Diplacanthus poltnigi n. sp., D. solidus n. sp., Gomphonchus nordicus n. sp. and Arcticacanthus bicostatus n. gen., n. sp.).