Dinohyus (Mammalia; entelodontidae) in the Sharps Formation, South Dakota

The anterior portion of a skull is referred to Dinohyus. The specimen is compared to Pelonax lemleyi Macdonald of Whitneyan age and Dinohyus hollandi Peterson of late Arikareean age. The specimen is the first entelodont to be reported from the Sharps Formation. It was found in a sandstone stream channel within the Sharps Formation from which a microfaunule was recovered. The microfaunal assemblage is similar to the Godsell Ranch Faunule and includes Plesiosminthus, which is recorded from the Sharps Formation for the first time. DURING the summer of 1967, Mr. Donald G. Davis, Seasonal Ranger-Naturalist at Badlands National Monument, South Dakota, discovered an entelodont snout in the Cedar Pass area of the Monument. The find was reported to R. W. Wilson, Director of the Museum of Geology, South Dakota School of Mines and Technology. A party consisting of both authors and James E. Martin, a museum assistant, collected the specimen, which has been catalogued as SDSM no. 675. We wish to acknowledge the generous cooperation of the authorities at Badlands National Monument for permitting us to collect the specimen. We also thank the authorities of the Department of Vertebrate Paleontology and the Frick Laboratory at the American Museum of Natural History, especially Morris Skinner, for showing us specimens of entelodonts and suggesting ideas on the Entelodotidae. We are grateful to J. C. Harksen, geologist for the South Dakota Geological Survey for lengthy discussions concerning the stratigraphy of the area. The specimen was located in a vertical cliff 70 feet above the top of the Rockyford Ash Member of the Sharps Formation (early Arikareean) at the base of a stream channel sandstone. Although the area from which the specimen came has not been geologically re-mapped in recent years it is familiar to those who have worked in the region. J. C. Harksen, one of the describers of the Sharps Formation, concurs in our referring these deposits to the Sharps. Harksen and the junior author have measured a 170-foot section from the base of the Rockyford Ash Member to the summit at the collecting site. The fossiliferous channel is unquestionably within the Sharps Formation as it appears in this region. Additional evidence that these deposits are at least time equivalents to the Sharps Formation of the type section area is furnished by a partial cranium of Capacikala gradatus (Cope), SDSM no. 673, found in place about three feet above the top of the Rockyford Ash near the entry to the canyon and a mandible of Palaeocastor nebrascensis (Leidy), SDSM no. 674, found 25 feet almost directly below the entelodont. Both of these beavers occur only in the Sharps Formation in the type section region according to Macdonald (1963, 1969). C. gradatus also occurs in the John Day Formation, Oregon. The stream channel sandstone is well-cemented. It is one of a number of channels found within the Sharps Formation. A few micrcfossils were recovered from the channel sandstone by aceti acid treatment. The SDSM specimens include: Lacertilia, Talpidae?, Domnina sp., Tamias sp., Proheteromys sp., Hitonkala andersontau, and Plesiosminthus sp. The presence of Plesiosminthus is recorded for the first time in the Sharps Formation. Macdonald (1963) reported all (except Plesiosminthus) of these from "a small, fossiliferous, stream channel deposit lying between the Brule Formation and the Quaternary alluvium... " This small assemblage is included in Macdonald's list of Sharps Formation elements. He also states, "The fauna indicates that this channel is referable to the Sharps formation." The similarity of the Godsell R nch Channel Faunule to that from the intercalated channel near Cedar Pass would inicate that Macdonald's inclusion of the Godsell Faunule as coming from the Sharps Formation is