RESEARCHERS CHALLENGE NOTIONS ON 5 MILLION-YEAR-OLD HORSES
A University of Utah professor and two colleagues are challenging the traditional notion that predecessors of the modern horse fed almost exclusively on grasses. Their findings may hold clues to eventually discovering what caused a major extinction in North America.
The three researchers, including U. geology and geophysics professor Thure Cerling, offer their conclusions in the scientific paper, "Ancient Diets, Ecology, and Extinction of 5 Million-Year-Old Horses from Florida." The paper appears in the Feb. 5 issue of the journal Science, and is co-authored by Bruce J. McFadden of the Florida Museum of Natural History at the University of Florida in Gainesville, and Nikos Solounias of the New York College of Osteopathic Medicine's Department of Anatomy.
The three scientists studied carbon isotopic data and wear marks on 5-million- year-old fossilized horse teeth uncovered in Florida. What they found was that not all horses at that time fed on grasses, as was previously supposed.
Early versions of the prehistoric horse had short-crowned teeth, which are particularly suited to a browsing diet of leafy and soft plants. Then, about 15 million years ago, horses' teeth evolved to be high-crowned, a characteristic indicative of grazing. These "tall" teeth would have been useful to combat the abrasive wear of grasses.
The new research questions those assumptions.
"What we found is that some were grazers, some were browsers, and some were mixed feeders," Cerling says.
Cerling says this time period, called the late Hemphillian, is a fascinating one to look at because it comes just before one of the biggest extinction events in North America. About 4-1/2 million years ago a number of species went extinct, including several species of horses. However, many aspects of that extinction continue to mystify scientists, Cerling says.
"The pattern (of extinctions) was not at all what we expected," he says. "The puzzle next is to figure out why some became extinct and others didn't. In a way, this research raises more questions than it answers."
Cerling says the Science article is just one facet of a larger project looking at environmental changes over the course of earth's history.
An upcoming study by researchers will look at the diets of modern vs. fossilized elephants.
RSS