University of Penn, Press
Release, 5/10/17
An ancient sink hole in eastern
Tennessee holds the clues to an important transitional time in the evolutionary
history of snakes. Among the fossilized creatures found there, according to a
new paper co-authored by a University
of Pennsylvania paleontologist, is a new species of snake that
lived 5 million years ago.
Steven
Jasinski, lead author of the new study, is a doctoral student in
Penn’s Department
of Earth and Environmental Science in the School of Arts & Sciences and
acting curator of paleontology and geology at the State Museum of Pennsylvania. He is
completing his Ph.D. under Peter
Dodson, a professor of paleontology in Arts & Sciences and
professor of anatomy in the School of
Veterinary Medicine at Penn.
The fossils come from the Gray
Fossil Site near East
Tennessee State University, where Jasinski and co-author David Moscato
pursued their master’s degrees.
This study, published in the Journal
of Herpetology, involved many hours of close examination of
hundreds of dark mineral-stained snake fossils. In the end, the biggest
surprise was the discovery of vertebrae that don’t match any known species of
snake, living or extinct. The researchers named the new genus and species
Zilantophis schuberti.
“Snakes don’t have arms or legs,
but they have high numbers of vertebrae,” Jasinski said. “These are often the
bones that paleontologists use to identify fossil snakes.”
Zilantophis bore uniquely broad
wing-shaped projections on the sides of its vertebrae. In life, these were
likely attachment sites for back muscles. These features are what inspired the
name of the new genus, derived from Zilant, a winged serpent in Tatar
mythology.
The species name, schuberti,
honors Blaine
Schubert, executive director of East Tenneessee State’s Don Sundquist
Center of Excellence in Paleontology and advisor to both authors during their
studies there. The name roughly translates to “Schubert’s Winged Snake” or
“Schubert’s Winged Serpent.”
Zilantophis was a small snake,
about 12 to 16 inches long.
“It’s about as large around as
your pointer finger,” said Jasinski. “This animal was probably living in leaf
litter, maybe doing a bit of digging and either eating small fish or more
likely insects. It was too small to be eating a normal-sized rodent.”
“These snake vertebrae are tiny,”
Moscato said. “Before we can study them, they have to be meticulously separated
from the sediment and other bones. This work is done by dedicated museum
workers, students and volunteers.”
Based on features of its
vertebrae, this new species is thought to be most closely related to rat snakes
(Pantherophis) and kingsnakes (Lampropeltis), both of which are relatively
common in North America today.
The Gray Fossil Site is one
of the richest fossil localities in the United States, particularly from the
Neogene period, which spans from 23 million to 2.58 million years ago. Based on
the extinct species found there, researchers estimate it to be between 7 and
4.5 million years old, straddling the boundary between the Miocene (23 to 5.33
million years ago) and Pliocene (5.33 to 2.58 million years ago) epochs. It is
one of the only sites of this age in the entire eastern U.S., making it an
important window into a poorly-known part of prehistory.
At the time that Zilantophis
dwelled there, the site was a sinkhole surrounded by forest, attracting a
variety of animals. The local fauna included ancient representatives of
familiar North American creatures such as bears, beavers and salamanders.
Others were more exotic, including unique species of rhinoceros, alligator and
the site’s famous red panda.
This is a time when the world was
moving in the direction of a modern climate and modern fauna,” Jasinski said.
The snakes, too, were a mix of
familiar and strange. In addition to the new species, there were ancient
species of garter snake (Thamnophis), water snake (Nerodia), rat snake
(Pantherophis), pine snake (Pituophis) and whip snake (Masticophis), among
others. In total, the researchers identified seven different snake genera at the
site, many of which are still found in east Tennessee today.
“Back in its day, the Gray Fossil
Site was a great environment for living animals to thrive and for dead animals
to fossilize,” Moscato said. “This makes for a paleontology goldmine,
positively packed with bones.”
This is the first survey of
snakes at this fossil site, and it focused specifically on identifying snakes
of the family Colubridae, the largest snake family, which includes about
two-thirds of all known living snake species.
“The Miocene was a time when the
snake fauna of North America was undergoing significant changes,” Jasinski
said.
In earlier times, boas, a group
known for their robust vertebrae, were widespread and common across northern
ecosystems, but as time went on the boas gradually retreated while colubrids,
typically smaller than boas, took over. This shift coincided with
continent-wide environmental change, including the replacement of forests with
grasslands and the spread of small mammals that may have provided a food supply
that fueled the expansion of colubrids.
“Zilantophis is part of this
period of change,” Jasinski said. “It helps show that colubrids were
diversifying at this time, including forms that did not make it to the present
day.”
The find and continued investigations
in this site help fill in details about the rich biodiversity of an ancient
ecosystem as it underwent a shift in climate — details that can inform our
understanding of the future as well.
“Snakes are important parts of
their ecosystems, both today and in the past,” Jasinski said. “Every fossil
helps tell a story, and all those pieces of evidence give scientists a clearer
picture of the past, as well as tools to predict how living communities may
respond to changes in the future.”
The study was supported by the National Science Foundation (Grant
0958985), Office of Research and Sponsored Programs at East Tennessee State
University and the Don Sundquist Center of Excellence in Paleontology.
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