Washington, Feb 7 : The discovery of crayfish body fossils and burrows in Victoria, Australia, has provided the first physical evidence that crayfish existed on the continent as far back as the Mesozoic Era.
Martin, a senior lecturer in environmental studies at Emory University, and a consortium of Australian scientists conducted the crayfish study.
The crayfish body fossils consist of an abdomen and two claws, and the fossil burrows are nearly identical to those made by modern crayfish in southeastern Australia.
"Studying the fossil burrows gives us a glimpse into the ecology of southern Australia about 115 million years ago, when the continent was still attached to Antarctica," says Martin, a senior lecturer in environmental studies at Emory University.
During that era, diverse plants grew in what is today Antarctica and dinosaurs roamed in prolonged polar darkness along southern Australia river plains.
The period is of particular interest to scientists since it is believed to be the last time the Earth experienced pronounced global warming, with an average temperature of 68 degrees Fahrenheit - just 10 degrees warmer than today.
Crayfish, due to their wide range, have long fascinated biologists. The fact that the marine animal, found in freshwater, has adapted to extremely diverse environments, is a matter of great interest for biologists studying them.
According to Martin, "Thomas Huxley, a colleague of Charles Darwin, was the first scientist to ponder how crayfish, which cannot survive in saltwater, could have spread to so many continents."
Such studies helped lay the groundwork for plate tectonics, which revolutionized the earth sciences in the 1960s through the theory that the continents were once connected. More recently, molecular biologists have theorized that all Southern Hemisphere crayfish originated in southeastern Australia.
"The evolution of Southern Hemisphere crayfish has challenged researchers since the 1870s," said Martin. "Only now, 140 years later, are we starting to put together the physical evidence for this evolution through the discovery of fossils," he added.