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Mazon Creek Best Of The Best Etacystis Communis Nitecki & Schram, 1976
RCFossils posted a topic in Member Collections
Etacystis communis is one of the more unusual animals that can be found in the Essex (marine) portion of the Mazon Creek deposit. Since being described, there has been much debate over what it might be. It has been suggested that it might be a Pterbranch hemichordate, a marine algae or a coelenterate. It is currently assigned as a hydrozoan. Etacystis is commonly referred to by collectors as the “H” animal. Relatively complete specimens bare a resemblance to the letter H. Unfortunately specimens are always incomplete with parts extending off the edges of the concretion. The animal is interpreted as having a main branch called a stolen that may serve as an attachment point to anchor itself into the substrate. It has also been suggested that this animal was free floating as numerous examples have been preserved with the jellyfish Octomedusa The stolen was flexible and would make up one leg of the letter H. The cross bar of the H is referred to as the peduncle. The peduncle bifurcated into 2 arms of different lengths. These arms make up the other leg of the letter H. Also attached to the peduncle is a strange sac like structure with a small aperture. This feature may be a mouth. On a few specimens, wart like bumps are preserved. These bumps could represent stinging cells, suckers or attachment points for tentacles. Etacystis could grow quite large. Based on incomplete specimens, it has been calculated that they could reach lengths of over 15 centimeters.