It is a puzzling creature. It is only found in Pit 11 of the Mazon Creek formation. The only species of the genera, it is Y-shaped, bilaterally symmetrical, and soft-bodied. It appears to have a mouth slit on the top between the two arms and a second opening on one side of the main body, presumably an anus, though there is no proof that it is an anus.
It is attached to the sea floor by a stalk attached to a round base. Oddly, I have a specimen that at least to my observation, appears to have a short tube-like structure in between the two arms near the mouth. I haven't gotten any reply from those whom I have asked about this yet.
Because of the lack of complex structures or apparent internal organs, it is believed that it must have been related to coelenerates (cnidarians) and may have used stinging nematocysts on its arms to capture prey. However, because of its bilateral symmetry and
second opening, it can't fit the technical definition of a coelenerate. Therefore, it is considered a separate group that may have broken off of the cnidarians and gone extinct as a failed evolutionary experiment. If it were to be classified as a coelenerate, the definition of coelenerate
would have to be changed and a new class would have to be added.
(left)My specimen of Escumasia roryi. Notice the odd tube in the center. Perhaps it is only a crack, but isn't a
conventional place for such a crack to appear. You can also see faintly, the curved slit that is the second opening
in the center of the main body. (right) A diagram of Escumasia. (below) Other specimens of Escumasia.
All of the photos and information I have written comes from "A Problematic Organism From th Mazon Creek (Pennsylvanian) of Illinois" by Matthew H. Nitecki and Alan Solem, Reprinted from Journal of Paleontology Vol. 47, No. 5, September 1973 pp. 903-907