What is "kouphichnium"

Kouphichnium is an ichnogenus that has been attributed to limulids (horseshoe crabs). Kouphichnium fossils resemble the footprints of birds, sometimes in conjunction with a medial line, and were initially thought to be bird or pterosaur tracks. The footprints are now believed to be the imprints of specialized limulid appendages, called pushers, terminating in four plates, used to push against the sediment. The medial line is left by the animal's telson.