Dickinsonia

Dickinsonia is a genus of extinct organism that lived during the late Ediacaran period in what is now Australia, China, Russia, and Ukraine. It had a round, approximately bilaterally symmetric body with multiple segments running along it. It could range from a few millimeters to over a meter in length, and likely lived in shallow waters, feeding on the microbial mats that dominated the seascape at the time.

As a member of the Ediacaran biota, its relationships to other organisms has been heavily debated. It was initially proposed to be a jellyfish, and over the years has been claimed to be a land-dwelling lichen, a placozoan, or even a giant protist. Currently, the most popular interpretation is that it was a seafloor-dwelling animal, perhaps a primitive stem group bilaterian, although this is still contentious. Among other Ediacaran organisms, it shares a close resemblance to other segmented forms like Vendia, Yorgia, and Spriggina, and has been proposed to be a member of the phylum Proarticulata or alternatively the morphogroup Dickinsoniomorpha. It is disputed whether the segments of Dickinsonia are bilaterally symmetric across the midline, or are offset from each other via glide reflection, or possibly both.