What is "birkenia"

Birkenia is a genus of extinct anaspid fish from Middle Silurian strata of Northern Europe, and Middle Silurian to possibly Earliest Devonian strata of Arctic Canada. Intact fossil specimens of B. elegans suggest the living animal reached a length of up to , and was an active swimmer. In addition to whole specimens and scale microfossils of B. elegans, which are found in Great Britain and Scandinavia, scales of a second species, B. robusta, are found in Late Silurian strata of Scandinavia and Estonia. The scales of B. robusta differ from those of B. elegans in that, as the specific epithet suggests, the scales of the former are more robustly proportioned than those of the latter.