This is the “Fossil Friday” post #104.  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 Twitter hash tag for contributions from around the world!

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This week, we have a Mazon Creek insect. This animal is Dasyleptis brongniarti a wingless insect similar to bristletails and silverfish.  We covered these animals back in Mazon Monday #44.  In that piece, we quoted Andy Hay in the “Creature Corner” book.  Also, included in that article were pictures from Don Auler.

Monura and Silverfish

Among restaurateurs and homemakers, the sight of a silverfish scurrying over the plumbing engenders panic and revulsion. Yet this very ancient insect, a Thysanuran, and its sister group, the Monura (extinct), are prize finds for the paleontologist. Both creatures were members of the Mazon Creek biota.

The taxonomy of animals that are descended from an ancient arthropod-like creature can get quite “sticky”. Authors have developed various phylogenetic charts. It is sufficient for our purpose to state that the wingless (Apterygote) and the winged (Pterygote) insects evolved from a common myriapod-like ancestor. Discoveries within the last 15 years have tentatively pushed the antiquity of the Hexapoda (Insecta) back to the Silurian. Myriapod-like animals, somewhat replaced by fluorapatite, were discovered in a dolomite quarry near Milwaukee, Wisconsin in 1985.

One scenario for Insect development goes in order to escape predators the ancestors of insects used their clawed “legs” to climb the primitive low-growing plants near shore, acclimating themselves to a terrestrial existence. Myriapods (millipedes) and Hexapods (insects) split off from the parent group becoming inhabitants of swampy, then moist soil. Differentiation continued until the Monurans split off from the group that would produce Thysanura and winged insects. All three groups are found in the concretions of the Mazon Creek area.

Monuran Silverfish (primitive insect) Collection of Kathy Dedina

Reconstruction 1987 by Kukalova-Peck J.

Today’s particular specimen comes from ESCONI board member Chris Berg.  He found it in Pit 11 near Torino Hill last year.  It opened just last week… you may have heard him yell out!  As he tells it, the look of the concretion left him with low expectations.  It sure is a good thing he picked it up… maybe those ugly looking concretions are the ones we should all be looking for?!?  Great find, Chris!  Thanks for sharing!