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ODU's Burdige Author of Article on Earliest Animal Life

David Burdige, an expert in biogeochemical oceanography and an Old Dominion University professor and eminent scholar of ocean, earth and atmospheric sciences, is an author of an article in the May issue of the journal Geology reporting the earliest geological evidence for animals on Earth.

The discovery places the existence of multicellular organisms around 850 million years ago, which is 200 million years earlier than the previously reported fossil or geochemical evidence of animals.

Canadian geologist Fritz Neuweiler of Laval University in Quebec is the first author of the article and Elizabeth Turner, a paleontologist from Laurentian University in Ontario, is also an author. The journal Geology is published by the Geological Society of America.

The scientists report evidence they found in the Northwest Territories of Canada indicating that primitive, sponge-like organisms existed during a period known as the Neoproterozoic interval of "hidden evolution." This is the gap between the time when primitive animals first evolved and the date-about 600 to 650 million years ago-of the oldest known geological evidence of animal life. The Neoproterozoic age was from about 779 to 1,083 million years ago.

To fill this gap, the scientists describe microscopic features they found in limestone about 850 million years old that are much like the texture known to develop today when aragonite crystals precipitate on the decaying connective tissue of sponges in sediment on the sea floor.

A complex texture of calcareous material and voids is produced as sponges decay in sediment at the ocean floor. This texture identified in modern sediments has been shown previously to be identical to those found in limestone about 500 million years old. Now, Neuweiler, Turner and Burdige have produced evidence of the texture in limestone that is 850 million years old. Their samples came from the Little Dal formation, which is renowned among geologists for its well-preserved record of Earth's evolution.

The animals, known as metazoans, that would have produced this new evidence did not have the canal system of sponges, which are the simplest form of animal life known today. The scientists say the organisms likely were a structured consortium of protists living in a shared scaffold of extra-cellular collagenous matrix up to a size of several centimeters.

The scientists note that an alternative interpretation of their evidence cannot be ruled out, but that features of the Little Dal reef indicate that the samples were not produced by macroalgae or some other grouping of unicellular organisms too small and simple to be animals. They describe their findings as "intriguing enough to stimulate further research aimed at unraveling the interval of hidden evolution, beyond the limits defined by conspicuous body fossils or metazoan biominerals."

Burdige and Neuweiler have collaborated previously on articles in the Journal of Sedimentary Research and the journal Sedimentary Geology, reporting research findings related to the calcification of sponges on the Great Bahama Bank. They began their collaboration in 2004 when Neuweiler was awarded a fellowship to work in Burdige's lab learning the fluorescence techniques that eventually formed the basis of the work presented in this article.

Burdige will serve as vice chair of the August 2009 Gordon Research Conference on Chemical Oceanography in Tilton, N.H., and will be chair of the 2011 biennial meeting. The chemical oceanography conference, which has been held since 1969, is part of the Gordon Research Conferences (GRC) lineup of international forums in biological, chemical and physical sciences. GRC is a nonprofit organization managed by and for the benefit of the scientific community.

The research of the ODU scientist focuses on biogeochemical processes in estuarine and marine sediments. He is the author of the textbook "Geochemistry of Marine Sediments," published in 2006 by Princeton University Press.

This article was posted on: June 1, 2009

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