This is the "Fossil Friday" post #158. 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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Today, we have a historically significant Mazon Creek fossil. If you visit Pit 11, it's almost a given that you will find an Essexella asherae. Whether it's a jellyfish or an anemone, it's a common Pit 11 fossil. Both are extremely rare in the fossil record. They have no hard parts, being just soft tissue... not much more than a bag of jelly-like fluid. Here's a description from NOAA.
Fascinating, elegant, and mysterious to watch in the water, take a jellyfish out of the water, and it becomes a much less fascinating blob. This is because jellyfish are about 95 percent water.
Lacking brains, blood, or even hearts, jellyfish are pretty simple critters. They are composed of three layers: an outer layer, called the epidermis; a middle layer made of a thick, elastic, jelly-like substance called mesoglea; and an inner layer, called the gastrodermis. An elementary nervous system, or nerve net, allows jellyfish to smell, detect light, and respond to other stimuli. The simple digestive cavity of a jellyfish acts as both its stomach and intestine, with one opening for both the mouth and the anus.
These simple invertebrates are members of the phylum Cnidaria, which includes creatures such as sea anemones, sea whips, and corals. Like all members of the phylum, the body parts of a jellyfish radiate from a central axis. This “radial symmetry” allows jellyfish to detect and respond to food or danger from any direction.
Jellyfish have the ability to sting with their tentacles. While the severity of stings varies, in humans, most jellyfish stings result only in minor discomfort.
We looked at E. asherae way back in Mazon Monday #14. And, just recently, a paper by ESCONI member Roy Plotnick questions the classification of Essexella asherae as a jellyfish and identifies it as a sea anemone... see Mazon Monday #155.
This particular specimen isn't the best example of E. asherae, but it has something missing from the ones you till find in Pit 11. Helen Asher is the namesake of Essexella asherae. She was a prolific collector. She sold and gave away many examples of the eponymous animal. Quite often, she would sign or at least offer to sign the specimen. Too bad more people didn't take her up on the offer, as there aren't many examples of these.
This interesting specimen was sent in by long time ESCONI member Jim Alann. Thanks for sharing, Jim! The signature makes this fossil priceless!
