ENIGMATIC ORGANIC-WALLED MICROFOSSILS FROM THE PENNSYLVANIAN (MISSOURIAN AND VIRGILIAN) OF IOWA, MISSOURI, KANSAS, AND OKLAHOMA

Enigmatic dark-black organic-walled microfossils have been recovered from Pennsylvanian (Missourian and Virgilian) shales in Iowa, Missouri, Kansas, and Oklahoma. The microfossils are less than 2.5 millimeters in length and 0.5 millimeters in diameter. They are cylindrical in shape and usually inflated on one side. Shoulders on each end slope to a narrow neck that connects one cylinder to the next one in a chain-like configuration. Most connections are marked by a simple enlargement of the necks. A small short tube is located on one end of the cylinder on the inflated part of the cylinder shoulder, but sometimes occurs on the neck. Exceptionally well-preserved specimens exhibit a wide flange arranged around the top of the small tube. The outer surface is very smooth, shiny, and without ornamantation. The wall thickness is usually less than 20 microns. These fossils are often associated with annelid worm (Polychaeta) jaw elements (scolecodonts) and conodnts, but the relationship between the two and the unknown microfossils is not known at this time. Most specimens are found in the gray shale facies of the core shale of cyclothems (as defined by Heckel) in abundances of up to several thousand per kilogram, but can also rarely be found in the more offshore parts of the transgressive and regressive limestones.