This is the "Fossil Friday" post #188. Expect this to be a somewhat regular feature of the website. We will post any fossil pictures you send in to [email protected]. Please include a short description or story. Check the #FossilFriday Twitter hash tag for contributions from around the world!
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In the marine areas of the Mazon Creek fossil deposit, it's very common to find blobs in opened concretions. Often these are left in the field in the search for rarer, more "interesting" fossils. There's even a poem "Ode to a Blob" (written by Rob Sula in 2002) to pay homage to these mostly unappreciated fossils.
ODE TO A BLOB
Oh, lowly blob,
Whose grave I did not rob.On the ground you sit
So round and nicely split.Were you but a few.
I'd bend to pick up you.But alas, you're not so rare.
And although I wish I'd care,
I left you lying there.Rob Sula (2002)
In 1979, Essexella asherae (Mazon Monday #14) was described as a jellyfish by Merrill Foster in "Soft-bodied coelenterates in the Pennsylvanian of Illinois". E. asherae was named for Helen Asher, a long time Mazon Creek collector. Suddenly, the blob had a name, which was good as E. asherae is the most common animal in the whole fossil deposit. Additionally, an identification as a jellyfish was important as jellyfish, lacking hard parts, are extremely rare in the fossil record.
More recently, Roy Plotnick, James Hagadorn, and Graham Young did an extensive study of E. asherae. Their findings were published in "The Mazon Creek Cnidarian Essexella: The World Turned Upside Down" in 2017. This research turns E. asherae on its head and changes its classification to sea anemone. Roy did a very nice presentation at the ESCONI Mazon Creek Open House in 2022.
Paul Mayer of the Field Museum brought the holotype specimen to the Open House.
A few weeks ago, we received an email and some nice photos from long time ESCONI member George Holub. He had an interesting story about Essexella to tell.
I was a long-time ESCONI member from the 1980's until I moved to Lake County in 2008. For over twenty-five years, I primarily collected Mazon Creek and regularly attended the Mazon Creek Open House. Recently, I attended the October 2022 Open House at Cantigny and was particularly interested in Dr Roy Plotnick’s presentation on “The Mazon Creek Cnidarian Essexella: The World Turned Upside Down”.
I’ve collected thousands of Essexella over the years, but had one specimen that I thought Dr Plotnick might be particularly interested in. I’ve not seen one like it. Attached below are several pictures of this specimen.
I emailed Dr Plotnick with these pictures. He discussed this with his colleagues who coauthored his recent article on updating Essexella's interpretation. They were interested and Dr Plotnick asked if he could borrow the specimen to photograph it and for further study. I made arrangements to loan this specimen to him and was interested to see if it could help reinforce their reinterpretation of this species. After his research he asked if I could donate the specimen to the Field Museum – it is now part of their collection.
The “red” arrows show the areas of particular interest. Upon death, the tentacles of anemones decay early. Roy took pictures and completed chemical analysis on the staining (iron?) which supported that they appear to be part of the tentacles. The staining is early decay remnants of tentacles.
Unfortunately, the specimen didn't make it into the paper, but it was donated to the Field Museum, where is now rests comfortably. Thank you for sharing this interesting story of an interesting animal, George!
