THE FIRST RECORD OF CENOMANIAN (LATE CRETACEOUS) INSECT BODY FOSSILS FROM THE KAIPAROWITS BASIN, NORTHERN ARIZONA

Cretaceous insect body fossils are not common in North America. Only a handful of localities have yielded substantial assemblages, with most of the specimens known from Turonian strata in New Jersey and Campanian strata in Canada. Cenomanian (93.6-99.0 Ma) insect body fossils are by comparison very rare, with only one previously published record of two cockroach specimens from the Dakota Formation of Minnesota. Fieldwork conducted in the summer of 2005 by personnel from Grand Staircase-Escalante National Monument uncovered a rich floral assemblage in a lacustrine mudstone within the Dakota Formation just south of the Utah-Arizona border near Lake Powell. To date, only three specimens have been obtained among the hundreds of plant fossils recovered. Ostracodes and rare small gastropods also occur in the sediments. Radioisotopic age dating of ashes at similar stratigraphic levels elsewhere in the Kaiparowits Basin indicate a middle Cenomanian age (ca. 96 Ma) for the insect bearing interval. Thus, these specimens are the only known of this age from the western United States. Of the three recovered specimens, one is a complete individual, whereas the other two preserve only abdomens. All three appear to represent the same taxon of odonate naiad, which supports the lacustrine origin for the encasing mudstone. Additional study is needed to determine if the taxon (taxa) represented is (are) new.