Octomedusa is a type Scyphozoan jellyfish.
It is the smallest described species of jellyfish that can be found in the Mazon Creek deposit. The bell can reach a maximum diameter of approximately 2 centimeters.
Like all Cnidaria from Mazon Creek, they are only found in the marine portion of the deposit.
In the faunal study that I have referenced in previous posts, Octomedusa made up .03% of 230,000 concretions collected.
Often times, only the bell is preserved.
Well preserved specimens will show 8 tentacles. Depending on orientation in the concretion, some specimens will show a crenulated edge around the bell.
Most specimens show very little raised detail and often appear as just a color difference in the rock.
A large “X” shaped mouth opening is preserved in some better specimens.
This first specimen shows most of the defining features.