Borings of the ichnogenus Gastrochaenolites have been found in limestone cobbles of the Morrowan (Early Pennsylvanian) Cane Hill Member of the Hale Formation in northwestern Arkansas. They were likely excavated by lithophagid bivalves, thus extending the earliest record of obligate bivalve boring back from the Triassic into the upper Paleozoic. These borings are herein referred to as G. anauchen n. ichnosp. Lithophagid borings may be rare in the upper Paleozoic because of the absence or scarcity of suitable substrates, such as scleractinian corals or carbonate hardgrounds. Additional upper Paleozoic bivalve borings will likely be discovered in other carbonate-rich rocky shore deposits.