Abstract. Nine longiconic cephalopod species of Desmoinesian (Middle Pennsylvanian; upper Carboniferous) pseudorthoceratid orthocerids are described from the Buckhorn Asphalt Lagerstatte (Boggy Formation) in Southcentral Oklahoma, Midcontinent North America. The fauna consists of Pseudorthoceras knoxense (McChesney), Arbuckleoceras tricamerae (Smith), Bitaunioceras buckhornense (Smith), Cyrtothoracoceras? sp., Dolorthoceras boggyense sp. nov., Smithorthoceras unicamera (Smith), Sueroceras oklahomense (Smith), Sulphurnites taffi sp. nov. and Unklesbayoceras striatulum sp. nov. Bitaunioceras buckhornense represents the first Pennsylvanian and therefore the oldest record of this genus. Arbuckleoceras gen. nov. differs from a comparable genus, Shikhanoceras, in possessing a weak exogastric curvature with a circular cross section of the conch and in lacking a conspicuous inflation at the embryonic shell. Smithorthoceras gen. nov. resembles orthoceratids rather than pseudorthoceratids in characters of camerae a...