Escumasia roryi is a species of enigmatic animal from the Mazon Creek site. Due to the large quantity of fossils, it has acquired a common name, that being "wye" or "y-animal" in reference to its shape.[1]
Escumasia ranges from 7.5cm (3.0in) to 20.5cm (8.1in) in length, with a stalk and two long arms making up most of this. These arms show no adaptations for capturing prey, thus their function is unclear. While being covered in cnidocytes and therefore a cnidarian affinity was proposed, this theory is unlikely due to an apparent anal slit on one side of the trunk showing that the organism was likely bilateral and had a "through-gut". The mouth is likely represented by a broad slit between the arms. The stalk is elongate, however rarely appears complete in fossils. The base is a bulbous disc with seemingly no surface features.[1]
Classification
While Escumasia does bear similarities with various cnidarians such as sea anemones, the presence of an anus and therefore a complete gut, alongside bilateral symmetry, makes this relationship problematic.[1] Slight traces of a central cavity within the fossils suggest a large "gastric cavity", likely the stomach. While it shares many similarities with "coelenterates", its bilateral symmetry and through-gut suggest otherwise, and therefore it is currently classified as Animaliaincertae sedis.
Etymology
The scientific name Escumasia roryi honours E. Scumas Rory, printer laureate of Illinois paleontology.[1]
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