FIRST MAMMALS AND OSTRACODES FROM THE PALEOGENE CLARON FORMATION, SOUTHWESTERN UTAH

The Claron Formation forms steep pink cliffs and hoodoos that adorn the cover of many geology textbooks and yet the formation’s history is not well known. It consists of conglomerates, sandstones, mudstones, and carbonates representing rivers, caliche soils, floodplains, and lakes. Gastropod molds and trace fossils are the most common fossils recovered from the formation. Actual shell material of unionids has been found in recent years, as well as shell hash deposits, but no vertebrate material has ever been reported and none of the invertebrate material has been age diagnostic. A locality has been found in the middle interval of the White Member of the Claron Formation on the Markagunt Plateau as a result of applying blind screen-washing techniques. The locality initially yielded only isolated fish bones and gill rakes, but with persistence produced one fragmentary rodent jaw from which the teeth had fallen out, probably during screen washing. One upper molar survived in good condition and is very close to Passaliscomys priscus originally described from low in the overlying Brian Head Formation on the Paunsaugunt Plateau. The age the type material is late middle Eocene (Duchesnean Land Mammal Age), suggesting that the White Member of the Claron Formation is also middle Eocene, most like equivalent to the Duchesnean. The locality also yielded ostracodes of Cypris sp. which also compare closely to those recovered from the lower part of the Brian Head Formation and coeval Eocene deposits in the Western Interior Basin.