This is the “Fossil Friday” post #281.  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!

---

Dasyleptus is an extinct genus of monurian insect. They are known from the Mazon Creek biota, other Carboniferous localities, and have been found in later deposits that date to the Permian.  They get their name for the single tail spike.  Their closest living relative today is the Silverfish.  In fact, some recent research suggests they may even be silverfish, instead of a distinct order as they are today. The species Dasyleptus is somewhat rare in the Mazon Creek biota.  It was described in 1957 by Sharov.  It’s found in the more terrestrial localities, but might also be present in concretions from Pit 11. (see Mazon Monday #44).

Chris Berg, who is currently the president of ESCONI, sent us in photos of a prime specimen. This fossil was collected from the Mazon River in 2025. Thanks for sharing this beautiful fossil, Chris!