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350-million-year-old fossils of aquatic sea animals
These colorful 350-million-year-old fossils are different species of an aquatic sea animal known as a crinoid. Geologists from The Ohio State University (OSU) discovered organic compounds sealed within the pores of these fossilized animal skeletons. The discovery of these fossils, which were uncovered in Ohio, Indiana and Iowa, has challenged the long-held belief of scientists that complex, organic molecules could not survive fossilization.
The geologists believe these fossilized crinoids, or "sea lilies," were buried quickly sometime during the Carboniferous Period, when North America was covered with vast inland seas. Isolated from the water above by layers of fine-grained sediment, their porous skeletons gradually filled with minerals, but some of the pores containing organic molecules were sealed intact. The researchers were able to extract these molecules directly from individual crinoid fossils in the lab and determined that different species of crinoid contained different molecules. The molecules appear to be aromatic compounds, called quinones, which are found in modern crinoids and other animals. Quinones sometimes function as pigments or as toxins to discourage predators.
"There are lots of fragmented biological molecules--we call them biomarkers--scattered in the rock everywhere," says William Ausich, a professor in the School of Earth Sciences at OSU and a co-author of the published study. "They're the remains of ancient plant and animal life, all broken up and mixed together, but this is the oldest example where anyone has found biomarkers inside a particular complete fossil. We can say with confidence that these organic molecules came from the individual animals whose remains we tested."
The study began when Christina O'Malley, who completed this work to earn her doctoral degree, noticed that some of the crinoids, though side by side and preserved in the same rock, were different colors. OMalley says although researchers noticed the color differences 100 years ago, it was not investigated and the analytical tools of today were not available then.
This research was supported in part by a grant from the National Science Foundation. To learn more, see the OSU news story Ancient fossilized sea creatures yield oldest biomolecules isolated directly from a fossil. (Date of Image: 2012)
Credit: Photo by William Ausich, courtesy of Ohio State University
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