Members of Syracuse University’s College of Arts and Sciences shed new light on a lingering mystery – one that has been forged millions of years.
A team of paleontologists led by Professor Catherine Newton has increased scientists’ understanding of whether Devonian marine animals, whose fossils settled in a unit of fundamental rocks in central New York known as the Hamilton group, were stable millions of years before they succumbed to waves of extinctions.
Drawing on 15 years of quantitative analysis with his colleague Professor Jim Brewer (who died in 2018), Newton went on to examine the structure of these ancient fossil societies, among the most well-known on Earth.
The group’s results, reported by the Geological Society of America (GSA), provide crucial new evidence of the unusual, long-term stability of Devonian societies.
Newton says such perseverance is a long-standing scientific puzzle. She and her colleagues tested the hypothesis that these ancient societies exhibited a coordinated stagnation – a theory that attempts to explain the emergence and disappearance of species through geological time.
Newton and Brauer, along with their student Willis Newman G93, found that Devonian marine societies differed in species composition more than theoretically anticipated. Newton indicates that they sought not to disprove the case of coordinated stagnation but instead to gain a more sophisticated understanding of when it was applicable. “Finding out more about the dynamics of these apparently stable Devonian societies is crucial,” she says. “Knowledge like this is of immediate relevance to marine societal changes in rapidly warming seas.”
Since geologist James Hall Jr. first published a series of volumes on fossils and devonian layers in the area in the 1840s, Hamilton’s collection has become a magnet for scholarly researchers and collectors alike. Today, Central New York is used a lot to test new ideas about large-scale changes in Earth’s creatures and environments.
During the Middle Devonian Period (roughly 380 to 390 million years ago), the animal composition of the region changed just over 4-6 million years. “It’s a great deal for marine invertebrate communities to remain stable, or” closed “, explains Newton, professor in the Department of Earth and Environmental Sciences.
She, Brewer and the student researchers spent years examining eight communities of animals that once inhabited a warm, shallow sea on the northern edge of the Appalachian Basin (which was eons south of the equator). When the organisms died, sediments from the sea floor began to cover their shells and exoskeletons. Minerals from the sediments gradually seeped into their remains, causing ossification. The process also preserved many of them in a living setting, while preserving the original shell materials in some locations.
These fossils currently inhabit the exposed base rocks all over central New York, ranging from soft, dark, and deep mudstones to hard, species-rich mudstones. “Societies near the top of the major rocks show more taxonomic and ecological diversity than those at the bottom,” Newton says. “We can compare the types of community and make it up over time. They are great sites.”
Coordinated recession has been a source of contention since 1995, when it was introduced. At the heart of the dispute are two model-based explanations: environmental tracking and insurance.
Environmental tracking indicates that animals track their environment. Here, periods of relative stagnation surrounded by coordinated extinctions or regional disappearances. When the environment changes, so does the marine fauna, says Newton, who is also a professor of interdisciplinary science and Dean Emerita of Arts and Sciences.
By contrast, environmental lockdown views marine animals as tightly organized societies, resistant to broad taxonomic change. Traditionally, this model has been used to describe the stability of the Lower Hamilton region.
Newton and her colleagues analyzed more than 80 sample sites, each containing about 300 samples. Special focus has been placed on the Cardiff members and Pecksport, two rock formations in the Finger Lakes region that are part of the ancient Marcellus sub-group, famous for its natural gas reserves.
“We found that the lower Hamiltonian animals, with two exceptions, do not have clear analogues among the higher animals. Therefore, our quantitative tests do not support the Ecological Lock Model as an explanation for the community stability in these animals.”
Newton considers this project a final tribute to Newman, a professor of biology at the State University of New York in Cortland, who died in 2014, and Brewer, who became seriously ill while finalizing the manuscript. “Jim knew he probably wouldn’t live to see it published,” Newton says, adding that Breuer died while submitting the paper to GSA.
She says this new work extends, and in some ways complements, the previous team’s research by analyzing societal structures in the Marcellus subgroup. “It has the potential to change scientists’ view of long-term stability in environmental societies.”