This is the “Fossil Friday” post #283.  Expect this to be a somewhat regular feature of the website.  We will post any fossil pictures you send in to esconi.info@gmail.com.  Please include a short description or story.  Check the #FossilFriday Bluesky/Twitter hash tag for contributions from around the world!

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A nice predatory polychaete worm from Mazon Creek is this week’s Fossil Friday. Fossundecima konecniorum was known as the Simple Jaw Worm before its formal description by Ida Thompson in  in 1979 in her famous paper “Errant polychaetes (Annelida) from the Pennsylvanian Essex fauna of northern Illinois. Palaeontographica Abteilung A Palaeozoologie-Stratigraphie“.  That same paper established many of the Mazon Creek worm species. Fossundecima konecniorum is thought to be a free swimming or grazing predator. Some specimens are known to exhibit ostracodes preserved on the gut line. (See Mazon Monday #150).

F. konecniorum was named for the Konecnys – Jim and Sylvia, who were prolific collectors and active in ESCONI for many years. The photo below shows Jim and Sylvia Konecny with Tony Sobolik giving a lifetime award to Lucy McLuckie.  Lucy is on the left, followed by Sylvia, Tony, and Jim.

This specimen was most likely found in the Pit 11 locality. Unfortunately, there isn’t any information about who and when it was collected.