( be related to such animals as jellyfis...)Virginia Tech, Nanjing Institute researchers discover half-billion year-old fossils

be related to such animals as jellyfishes and worms. Other scientists, however, believe that they may be plants or fungi. Twenty years ago, however, Adolf Seilacher, a paleontologist now retired from University of Tubingen (Universität Tübingen) and Yale University, argued that many Ediacara organisms were built of tube-like elements and are only distantly related to living animals. "But direct observation of the hypothesized tube-like elements has been difficult because such tubes tend to be deflated and squashed prior to their preservation in sandstones," Xiao said.

This may change with the new discovery of Ediacara fossils from fine-grained limestone of the Dengying Formation in South China by Xiao and his collaborators. "The Ediacara fossils from China were not deflated before they were incorporated in the rock," said Shen, "instead, they are preserved three-dimensionally in the rock." Using serial thin sectioning techniques, Shen and Xiao cut the decimeter-sized fossils into many paper-thin slices and looked at them under a microscope. They saw organic remains of millimeter-sized tubes that were the building blocks of the Ediacara fossils from China. Their discovery thus directly confirms Seilacher's hypothesis.

The new fossils also help to refine the Seilacher hypothesis. Seilacher originally hypothesized that Ediacara tubes had closed ends and were filled with cytoplasm, or cell contents. The fossils from China, however, appear to have an open end that is connected with the external environment. Thus, Xiao and his colleagues infer that the tubes of their Ediacara fossils were probably not filled with cytoplasm.

Ediacara organisms had no shells or bones. How could such soft and delicate organisms be preserved in rocks? Working with Geosciences Professor Fred Read at Virginia Tech, Geology Professor Guy Narbonne at Queen's University, and paleontologist James Gehling at South Australia Museum, Xiao and his colleagues carefully examined
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Source:Virginia Tech

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