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Lake-bed trails tell ancient fish story

Date:
May 6, 2010
Source:
Emory University
Summary:
The wavy lines and squiggles etched into a slab of limestone found near Fossil Butte National Monument are prehistoric fish trails, made by Notogoneus osculus as it fed along a lake bottom, according to experts.
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Is it possible to track the movements of an extinct fish in a long-gone lake? It is if you are Emory paleontologist Anthony Martin. He's found that wavy lines and squiggles etched into a slab of limestone found near Fossil Butte National Monument are prehistoric fish trails, made by Notogoneus osculus as it fed along a lake bottom.

He led a detailed analysis, published in PLoS One, that gives new insights into the behavior of the extinct N. osculus, and into the ancient ecology of Wyoming's former Fossil Lake.

"We've got a snapshot of N. osculus interacting with the bottom of a lake that disappeared millions of years ago," Martin says. "It's a fleeting glimpse, but it's an important one."

Fossil Lake, part of a subtropical landscape in the early Eocene Epoch, is now a sagebrush desert in southwestern Wyoming, located in Fossil Butte National Monument and environs. The region is famous for an abundance of exquisitely preserved fossils, especially those of freshwater fish.

Trails left by these fish, however, are relatively rare. The National Park Service had identified about a dozen of them and asked Martin to investigate. Martin specializes in trace fossils, including tracks, trails, burrows and nests made by animals millions of years ago.

One of the fish trace fossils especially intrigued Martin. In addition to apparent fin impressions of two wavy lines, it had squiggles suggesting oval shapes. "The oval impressions stayed roughly in the center of the wavy lines and slightly overlapped one another. I realized that these marks were probably made by the mouth, as the fish fed along the bottom," Martin says.

He then deduced that the trace was likely made by N. osculus -- the only species found in the same rock layer whose fossils show a mouth pointing downward.

Martin brought his detailed notes, photos and sketches of the trace fossil back to Atlanta, where he enlisted the aid of disease ecologist Gonzalo Vazquez-Prokopec and geographer Michael Page, two of his colleagues in Emory's Department of Environmental Studies.

Vazquez-Prokopec, who does digital spatial analyses of geographic patterns of diseases and pathogens, applied similar techniques to the trace fossil data. The results showed a mathematical correlation between the trace impressions and the mouth, tail, pelvic and anal fins of an 18-inch N. osculus.

"This provides the first direct evidence of N. osculus bottom feeding," Martin says. "Not only that, the fish was bottom feeding in the deepest part of the lake. Previous research had suggested that the bottom of the lake had such low levels of oxygen that it was hostile to life. Our analysis indicates that, at least seasonally, some fish were living on the lake bottom."

The scientists were also able to calculate how the fish was moving, and the pitch and yaw of its swimming motion. "The trace fossil lines look simple, but they're not so simple," Martin says, explaining that even the gaps in the lines carry information. "As the British say, 'Mind the gap.'"

"All three of us believe in making scientific data as open and assessable as possible," Martin says, adding that he thinks it may be the first collaboration between a paleontologist, a disease ecologist and a geographer. "This opens up a new technique for studying trace fossils that we hope other people will try and test."


Story Source:

Materials provided by Emory University. Note: Content may be edited for style and length.


Journal Reference:

  1. Anthony J. Martin, Gonzalo M. Vazquez-Prokopec, Michael Page, Andrew Allen Farke. First Known Feeding Trace of the Eocene Bottom-Dwelling Fish Notogoneus osculus and Its Paleontological Significance. PLoS ONE, 2010; 5 (5): e10420 DOI: 10.1371/journal.pone.0010420

Cite This Page:

Emory University. "Lake-bed trails tell ancient fish story." ScienceDaily. ScienceDaily, 6 May 2010. <www.sciencedaily.com/releases/2010/05/100506121854.htm>.
Emory University. (2010, May 6). Lake-bed trails tell ancient fish story. ScienceDaily. Retrieved March 28, 2024 from www.sciencedaily.com/releases/2010/05/100506121854.htm
Emory University. "Lake-bed trails tell ancient fish story." ScienceDaily. www.sciencedaily.com/releases/2010/05/100506121854.htm (accessed March 28, 2024).

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