Reassessment of Ischnacanthus?scheii Spjeldnaes (Acanthodii, Ischnacanthiformes) from the latest Silurian or earliest Devonian of Ellesmere Island, arctic Canada

• Published in: Canadian Journal of Earth Sciences
• Main Author: Burrow, Carole J.
• Other Authors: Sues, Hans
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2013
• Subjects: Arctic; Canada; Canadian Arctic Archipelago; Cornwallis; Cornwallis Island; Devon Island; Ellesmere Island; Greenland; Nunavut; Arctic Archipelago; North Greenland
• Online Access: http://dx.doi.org/10.1139/cjes-2013-0068; http://www.nrcresearchpress.com/doi/full-xml/10.1139/cjes-2013-0068; http://www.nrcresearchpress.com/doi/pdf/10.1139/cjes-2013-0068

Articulated specimens of jawed fishes, and assemblages of disarticulated elements that can be assigned to a single biological species, are extremely rare from pre-Devonian deposits. The acanthodian species Ischnacanthus? scheii Spjeldnaes is based on a monospecific assemblage, comprising fin spines, dentigerous jaw bone fragments and scales, from the ?Siluro-Devonian boundary beds of the Devon Island Formation in central west Ellesmere Island, Canadian Arctic Archipelago, Nunavut. A new examination of the type material, in particular by scanning electron microscopy and thin sectioning of scales, shows that the species is a porosiform poracanthodid that is now assigned to Radioporacanthodes scheii comb. nov. Scales of the same species are also recognized from the upper Pridoli of Cornwallis Island and the ?Pridoli or Lochkovian of north Greenland.