This is the “Fossil Friday” post #86.  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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There are a few species of shark egg cases known from Mazon Creek.  Today, we have a somewhat common, but no less beautiful specimen of Palaeoxyris prendelli.  Remember, that is common for a Mazon Creek shark egg case fossil.  In general, shark egg cases are very rare in the fossil record.  P. prendelli was described by Leo Lesquereux in 1870 from fossils found in Lancashire, England.  Lesquereux was a Swiss born bryologist and a pioneer in American paleobotany. In George Langford’s time, these fossils were thought to be a plant part. We now know that was wrong,  For more information, see the Field Museum guide written by Jack Wittry.  Here’s what Wikipedia has to say about Palaeoxyris.

Palaeoxyris is the prehistoric shark egg capsule morphotype of the family Hybodontidae with a predominant occurrence in ancient freshwater environments. They comprise a beak, a body and a pedicle, with the beak merging into the body. They display a conspicuous right-handed spiral of ridges around the body, and in some cases, the pedicle.^[1] Originally described as plant remains and controversially discussed within the floral kingdom it took decades before their true nature as animal eggs was revealed.^[2]

The specimen below comes from long time ESCONI member Marie Angkuw.   Thanks for the contribution, Marie!  It’s very nice!  It seems like you have been finding quite a bit lately…  She sent it in with this short description.  No locality information was given.

This nice oval concretion shows hammer marks and I suspect was tossed away. Later, a chip revealing the fossil must have freeze/thawed its way off.