This is the “Fossil Friday” post #274.  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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Palaeoxyris prendeli is a shark egg case from the Carboniferous Period.  These egg cases are believed to have been produced by hybodont sharks.  P. prendeli was named by Leo Lesquereux in 1870.  At that time, it was believed to be a plant part, maybe a seed pod.  The name palaeoxyris comes from the the flowering plant genus Xyris, which grows in swampy environments in the tropics and subtropics.  There are a number of species found in India.  Where they are commonly known as yellow-eyed grasses and are characterized by their grass-like leaves and yellow iris-like flowers.

This particular specimen was found in the coal mining areas around Terre Haute, IN.  The fossils from that area of Indiana date to about 305.5 million years ago, which makes them a little younger than Mazon Creek.  To find out more about Carboniferous shark egg cases, see Jack Wittry’s guide on the Field Museum’s website. 

Here is the specimen before cleaning.  

After cleaning with a little vinegar.