REVISION OF THE ICHNOGENUS ARTHROPHYCUS HALL, 1852, AND COMMENTS ON ITS BIOSTRATIGRAPHIC AND BIOGEOGRAPHIC SIGNIFICANCE

Arthrophycus, an ichnogenus best known from the Silurian of New York (USA), has become a “wastebasket” taxon that merits revision. Arthrophycus is a well-known fossil with specimens reported from localities around the world, including all seven continents and twenty-eight countries, and it is often cited as having biostratigraphic utility. Stratigraphically, Arthrophycus is best known from Ordovician and Silurian strata, but other instances have been reported from the Proterozoic to the Tertiary. Reports of Arthrophycus from Devonian and Carboniferous strata have been questioned, and post-Paleozoic occurrences are highly suspect. Imprecise or overly-brief descriptions and ambiguous or unclear illustrations, drawings, and photographs of specimens regarded as Arthrophycus have resulted in taxonomic uncertainty and have led to confusion over the biostratigraphic utility of the ichnogenus.

Of twenty-two described ichnospecies of Arthrophycus, as few as five are here considered acceptable; many Arthrophycus ichnospecies are inadequately described or may not be Arthrophycus at all. Only Paleozoic occurrences are considered valid, including some specimens from the Cambrian, Devonian, and Carboniferous, challenging the notion that Arthrophycus is confined to the Ordovician and Silurian.