Acritarchs and Spores from the Upper Devonian Lime Creek Formation, Iowa, U.S.A.

A well-preserved acritarch and spore assemblage is described from an 18.3 m section of the Upper Devonian (upper Frasnian, Palmatolepis gigas conodont zone) Juniper Hill and Cerro Gordo members of the Lime Creek Formation, Floyd County, Iowa, USA. The palynomorph assemblage comprises 23 genera and 43 species of acritarchs, and 12 genera and 12 species of spores. We propose two new acritarch genera, Centrasphaeridium and Pratulasphaera; nine new acritarch species; and two new spore species. In addition, one new combination, Dictyotidium craticulum (=Cymatiosphaera craticula Wicander and Loeblich 1977) is proposed. The palynomorph assemblage indicates a nearshore, normal marine environment, consistent with the interpretation provided by the associated shelly fauna. Comparison with other Frasnian palynomorph assemblages indicates similarity mostly in terms of long-ranging and cosmopolitan acritarch species while of the 12 miospore species present, only Geminospora lemurata and Laiphospora membrana have been previously reported.-Authors