Arthrorhachis Hawle and Corda, 1984 (Agnostida) in the Prague Basin (Barrandian area, Czech Republic) revisited
Abstract
The agnostid Arthrorhachis Hawle and Corda, 1847 coming from the Prague Basin (type area of its occurrence, including type species of the genus) is revised. The taxonomical position of all earlier established type specimens is revised and clarified.
All available material, including the recently collected specimens is described and discussed. The glabellar imprints are for the first time described on the material from the Barrandian area.
The stratigraphical distribution of the two established species, A. tarda (Barrande, 1846) and A. pragensis (Přibyl and Vaněk, 1968) is evaluated. Although Arthrorhachis belongs to the latest agnostids, its representatives are locally common in the siltstones of the Zahořany, Bohdalec and especially Králův Dvůr formations (upper Sandbian-upper Katian interval).
In the Prague Basin, the last specimens of Arthrorhachis persist probably up to the onset of the Hirnantian glaciation. The classical concept of the "Lejškov facies" is discussed.