CENOMANIAN (LATE CRETACEOUS) MAMMALS FROM THE DAKOTA FORMATION IN CEDAR CANYON, SOUTHWESTERN UTAH

Mammals have been previously reported from the middle member of the Dakota Formation around the margins of the Paunsaugunt Plateau 65-90 km east of Cedar Canyon. The age of the fauna in the Paunsaugunt region is probably middle Cenomanian based on radiometric dates and stratigraphic proximity (15-20 m below) to the well dated upper Cenomanian marine upper member. Two localities have been discovered by “blind-washing” methods in the middle member of the Dakota Formation in Cedar Canyon, east of Cedar City. These localities are more than 100 m below the upper Cenomanian upper member of the Dakota Formation which has been dated in Cedar Canyon based on agglutinated foraminifera and ostracodes. To date a relatively small amount of matrix (~1,000 kg) has been processed by screen washing from these localities. Among the multituberculate mammals recovered are Paracimexomys-like multituberculates, a new small species of Cedaromys, Dakotamys malcolmi, and Cimolodontidae genus and species undetermined. The therian fauna includes a spalacotheriid symmetrodont, a boreosphenidan Picopsis-like taxon, and at least one new species of “Alphadon.” The presence of Dakotamys malcolmi, conspecific with a taxon recovered from localities to the east, suggests an approximate age equivalency of these two faunas. The new species of “Alphadon” is distinctly more primitive than either “A.” lillegraveni or “A.” clemensi previously described from the Paunsaugunt region and may indicate that the Cedar Canyon fauna may be slightly older than the fauna from the Paunsaugunt region, possibly being as old as early Cenomanian but certainly no older.