Fossils of Uncertain Affinity from the Upper Devonian of Iowa

Thousands of specimens of the enigmatic fossil Gluteus minimus (new genus, new species) occur in a 5-centimeter-thick interval within the Maple Mill Shale and in equivalent deposits of the Devonian of eastern Iowa. They are roughly lenticular, bilobed fossils up to 11 millimeters in diameter and 8 millimeters thick. These objects, consistently asymmetrical in the same direction, defy placement in any known higher taxon when their morphology, histology, and apatitic composition are considered.