GERSHWIN, L.*; LIPPS, J. H.: Some new thoughts on some old animals

The Ediacaran fauna has been subject to diverse and sometimes wild interpretations, especially during the last decade or so when it has become fashionable to interpret the group as non-metazoan. Our investigations have shown that some forms can be better understood in terms of poorly known modern cnidarians, while other forms may provoke more intrigue than previously thought. First, the strange, chambered Ventogyrus bears a striking resemblance to the poorly known hand-grenade-like siphonophores in the family Rhodaliidae. Second, the earliest known echinoderm, Arkarua, may not actually be pentamerous as originally thought, but rather variable in its symmetry, as well as possibly possessing curved spines similar to those found in modern crinoids. Third, one of the specimens in the type series of the earliest known sponge, Paleophragmodictya, possesses many of the qualities one would hope to find in a spectacular medusa fossil, namely, a strongly tetramerous body plan, marginal tentacles, and a velum. Fourth, some specimens of the enigmatic triradial Tribrachidium show a well-defined, bilateral, internal vascular or skeletal structure. These observations indicate the need for a parsimonious reassessment of Ediacaran relationships.