Chengjiang Archisaccophyllia Primitive Sea Anemone

Description: This is an example of the incredible diversity of early life known from the Chengjiang Biota. The diversity of soft-tissue fossils is astonishing: algae, medusiforms, sponges, priapulids, annelid-like worms, echinoderms, arthropods (including trilobites), hemichordates, chordates, and the first agnathan fish make up just a small fraction of the total. Numerous problematic forms are known as well, some of which may have represented failed attempts at diversity that did not persist to the present day.

The original describers believe it is an early Cnidaian, a sea anemone much like those to come later. The striated stem and rounded base are indeed evocative of such an assignment. This specimen is known as Archisaccophyllia kunmingensis, and differs from Xianguangia by virtue of less tentacles (typically 12 vs 16) and a more flexible body. Indeed while both have been considered Cnidarians, the describers of this taxon feel Xianguagia is not an actinarian. Archisaccophyllia seemed to be a gregarious animal; a single colony of 15 square meters was found to possess over 350 individuals.

Reference: Lethaia, Vol 38 pp 193-203 (2005).