A Walk Through Time

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700 Million Years Ago

Ediacaran organisms leave quite an impression, which is rare for soft-bodied biota. Beautifully bizarre, their shapes vary from leaflike to three-armed to flat to "quilted." In the shallow coastal seas of the "Garden of Ediacara," photosynthetic and chemosynthetic symbionts help some of these organisms grow large, while others graze on plentiful bacteria. These gelatinous creatures have no hard parts and predators. Theirs was a pre-armored world.

Ediacaran fossils are found all over the world. Evolutionary biologists disagree about the nature of these enigmatic beings, since none of their relations survive to tell the tale. The delicate Ediacarans, an evolutionary experiment in life forms, go gently into that good night.

Orphrydium versatile is a colonial ciliate in the process of becoming what we humans call an "individual." These "green jelly ball" colonies are microbial worlds within worlds, consortia of several hundred different kinds of microbes. Orphrydium may be the closest living analogue of the large photosynthetic and chemosynthetic protoctist colonies of the quilted soft-bodied wonders of Ediacara.

Top-left: Green jelly ball colony. (Photograph by Brian Duval with Lynn Margulis)

Top-right: A mystery fossil with no known relatives, the species Pteridinium occurs abundantly on the surface of Precambrian sandstones in Namibia, southwest Africa, and other parts of the world. Some scientists consider Pteridinium to represent the earliest known animal fossil; others are skeptical that the organism was related to animals at all. (Photograph by Mark A. McMenamin)

Mid-left: Lots of zooids ("little eyebrows") in the jelly ball. (Photograph by Brian Duval with Lynn Margulis)

Bottom: Zooids, up close and personal. (Photograph by Brian Duval with Lynn Margulis)

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