Devonian Spores in a Middle Silurian Reef

Abstract

A subsurface core from the Tilden reef (Middle Silurian) in southern Illinois contains a large and diverse assemblage of hystrichospherids and plant spores. The plant spores are restricted to sinuous cracks filled with calcite and brownish-gray clay. The miospore assemblage is dated late Middle or early Late Devonian, and thus the fissure fillings represent a “stratigraphic leak”. Failure to recognize this phenomenon could result in misleading age determinations. The spore assemblage is dominated by cingulate miospores of the genera Stenozonotriletes and Retusotriletes and by spores with perisporal membranes assignable to Diaphanospora. Seventeen new species are described and illustrated: one each of Deltoidospora, Anapiculatisporites, Verrucosisporites, Cristatisporites, Rhabdosporites, Ancyrospora, and Endosporites; two each of Converrucosisporites and Retusotriletes, and three each of Stenozonotriletes and Diaphanospora.