FL (2/4/98)- A bit of scientific detective work with some 5 million year-old
horse teeth provides new information on the climate and ecology of prehistoric
Florida while calling into question current concepts of horse evolution.
Paleontologists at the University of Florida combined two scientific techniques
in a new way to analyze fossilized horse teeth that had been found in mine
shafts. Dr. Bruce MacFadden and colleagues were able to cross-reference data
obtained from radioisotope carbon dating of the teeth with analyses of scratches
and pits found in the teeth.The combined data suggest that the horses ate
a combination of foods from a savannah-like grassland interspersed with lush
forests and marshy wetlands.
of Florida paleontologist Bruce MacFadden measures fossil horse teeth.
MacFadden and his team ground up small parts of the horses' tooth enamel
and chemically analyzed them via mass spectrometry. This yields data on the
kind and proportions of carbon in the teeth. Soft vegetation and grasses have
different spectrometric signatures.
"This study is noteworthy because it's the first to be published that looks
at the combination of these two techniques to understand ancient diets and
the ecology of a particular group of extinct mammals. These techniques are
revolutionizing our ability to understand what prehistoric animals ate. Before
now, the only way we could figure that out was by looking at their teeth.
Not only that, our research challenges the traditional view that the form
and structure of the teeth alone can tell you something about diet," said
MacFadden's research involved six species of extinct horse known as the Bone
Valley Horses. Evolutionary studies indicate that horse living 55 million
years ago had short-crowned teeth, suggesting a diet of leafy and soft plants.
But 20 million years ago things began to change dramatically, and an explosion
of new horse species arose, many with high-crowned teeth better adapted for
grazing on abrasive plants, particularly grasses. The Bone Valley Horses all
had high-crowned teeth. But studies of pits and scratches on the teeth suggest
a diet of soft leafy materials and hard scratchy grasses, either alone or
"This is the first time we've been able to use other techniques to challenge
this assertion that the height of a tooth is uniquely indicative of diet,"
"This is a milestone study," said John M. Rensberger, a professor in the
department of geological sciences and curator of vertebrate paleontology at
the University of Washington's Burke Museum. "The research by MacFadden and
colleagues provides impressive quantitative evidence that permits precise
statements to be made about a partitioning by these related genera of dietary
resources between grass and leaf floras."
Learning about changes in the diets of ancient animals is important because
it provides clues about how species interacted at certain points in time,
MacFadden said. "If all the animals in a particular area were feeding on the
same resources and there was a big extinction, you might suspect something
about their diet affected the extinction.
"It also gives a lot of information about ancient environments," he said.
"If you have a community of ancient animals that are all found to be grazers,
then you can infer that the environment of the local habitat was grassland.
If the animals are all browsers, then you can infer that there was more forest
or scrub. It can give you a broad perspective over millions of years what
animals fed upon and what changes occurred in the plant communities."
The research appears in the Feb. 5, 1999 issue
of the of the journal Science.