A NEW ICHNOSPECIES OF ARTHROPHYCUS FROM THE LATE CARBONIFEROUS (PENNSYLVANIAN) OF MICHIGAN

A unique ichnofossil assemblage from Pennsylvanian-age sandstones near Eaton Rapids, Michigan, USA, comprises sinuous traces preserved in convex hyporelief, showing the transverse ridges and median grove typical of the ichnogenus Arthrophycus. The Eaton Rapids traces do not branch, but they do show pseudo-branching (known from other Arthrophycus specimens) and are among the smallest structures (millimeters in diameter) attributed to this ichnogenus. The Michigan traces are distinct from other ichnospecies of this taxon in showing a pronounced alignment of the burrows, as opposed to the multi-planar, interweaving, “bundled” nature typical of the ichnogenus, and we assign the Michigan specimens to a new ichnospecies of Arthrophycus. The “paralleling behavior” of the new taxon may reflect a strategy of the trace-maker to avoid previous burrows and reflect differences in resource availability or current energy. This new taxon extends the geographic range of Arthrophycus into Michigan and confirms the occurrence of this ichnogenus in Upper Carboniferous strata.