Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New species of ancient rodents hint at what could be world's oldest grasslands

24.07.2012
Analysis of fossilized teeth indicate early open, dry environment in Chilean Andes

A paleontological team that includes scientists from the American Museum of Natural History; University of California, Santa Barbara; and Case Western Reserve University has described two ancient species of South American rodents, including the oldest chinchilla, a discovery that substantiates what might be the earliest grasslands in the world.


This is a reconstruction of Mesoprocta hypsodus, an extinct, 13-million-year-old Bolivian relative of the new dasyproctid rodent Andemys termasi from Chile.

Credit: V. Simeonovski & D.A. Croft

The two new species lived near a chain of volcanoes about 32.5 million years ago in what are now the steep slopes of a river valley in the Chilean Andes. Studies of the teeth of the ancient chinchilla support evidence from other species in the concurrent fauna indicating that the animals inhabited an open and dry environment 15 million years before grasslands emerged elsewhere in the world. The research is published this week in American Museum Novitates, a peer-reviewed scientific journal of the American Museum of Natural History.

"The new chinchilla fossil provides important new evidence that early rodents joined other South American mammals in evolving ways to cope with an abrasive diet long before horses, sheep and other mammal groups on other continents 'invented' similar adaptations for making their teeth wear out more slowly while eating tough grasses," said John Flynn, Frick Curator of Fossil Mammals and dean of the Richard Gilder Graduate School at the American Museum of Natural History, who is a co-author of the paper.

Flynn and colleagues have explored the fossil history preserved in the Chilean Andes for the past 25 years. In the Tinguiririca River valley, an area near the border of Chile and Argentina once thought to be inhospitable to fossils because of the dominance of volcanic rocks, the researchers have uncovered hundreds of specimens, including the two newly named species of early South American rodents.

The new specimens—Andemys termasi, for which the genus name means "mouse of the Andes" and the species name refers to the nearby town of Termas del Flaco, and Eoviscaccia frassinettii, named for the late Daniel Frassinetti, who was a longtime collaborator and head of paleontology at Chile's National Museum of Natural History—are the second-oldest rodents ever discovered in South America. The oldest are recently discovered 41-million-year-old rodents from Peru. The new species are distinguished from the older rodents by many features of their teeth.

Rodents are known and named for their ever-growing incisors, which they use for gnawing. Yet the back or "cheek" teeth, used for grinding, have a special story to tell in this case: one that focuses on the crown, the portion of the teeth protected by long-wearing enamel. While the Peruvian rodents had cheek teeth with a crown extending only to the gum line, one of the new ancient Chilean rodents has high crowns that extended underneath the gums, enabling it to eat gritty foods like grass.

"The Tinguiririca chinchilla replicates a dental pattern appearing in many other South American herbivores such as Notoungulates—hooved animals that are now extinct—at that time. This pattern is called hypsodonty," said lead author Ornella Bertrand, who conducted the research through the Museum's Annette Kade Graduate Student Fellowship Program.

Hypsodonty, the quality of having high-crowned teeth, is a trait that emerged in multiple kinds of animals, such as horses, goats, and cows. Hypsodonty is generally interpreted as an adaption that arose in response to the spread of grassy environments.

The age of the fossils and the high-crowned teeth of the new chinchilla and many other mammals in the same fauna suggest to researchers that the mountainous Tinguiririca River valley was a grassy plain at the time the debris from a volcanic eruption buried them. This means that the Chilean Andes supported plains environments some 15 million years before such ecosystems are known on other continents.

"In addition to being preserved in unusual volcanically derived sediments, the new rodent species are notable for coming from what is assuredly one of the most spectacularly scenic and rugged sequences of fossil mammal localities in the world," said co-author André Wyss, of the University of California, Santa Barbara.

The new rodent species indicate that there was explosive diversification on South America when it was an island continent, before the formation of the Isthmus of Panama about 3.5 million years ago.

Eoviscaccia frassinettii, which is related to the modern chinchilla, and, Andemys termasi, related to a lesser-known group that includes the agoutis, a group of short-tailed rat-like species also native to South and Central America, belong to what originally was an exclusively South American group of rodents called caviomorphs.

Caviomorph rodents include the New World porcupines, capybara, guinea pig, and many others. Based on the fossil record and evolutionary relationships, the ancestors of these animals are thought to have come to South America from Africa on rafts of debris. Once on the massive island, caviomorphs diversified into some of the unique species we see today.

"The island continent of South America represented a land of evolutionary opportunity for the ancestors of chinchillas and other caviomorph rodents," said co-author Darin Croft of Case Western Reserve University in Cleveland. "These remarkable rodents came to fill an amazing variety of ecological niches and today are among the most characteristic Neotropical mammals."

The specimens of both new species are part of the collections of the National Museum of Natural History of Chile. The Andemys termasi specimen is featured in the American Museum of Natural History's exhibition Extreme Mammals, which is currently being shown at The Field Museum in Chicago. Funding for this work was provided by U.S. National Science Foundation collaborative research grants to A.R. Wyss (DEB-0317177) and J. J. Flynn (DEB-0317014 and DEB-0513476).

Kendra Snyder | EurekAlert!
Further information:
http://www.amnh.org

More articles from Life Sciences:

nachricht Seeing on the Quick: New Insights into Active Vision in the Brain
15.08.2018 | Eberhard Karls Universität Tübingen

nachricht New Approach to Treating Chronic Itch
15.08.2018 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Im Focus: Lining up surprising behaviors of superconductor with one of the world's strongest magnets

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

 
Latest News

Unraveling the nature of 'whistlers' from space in the lab

15.08.2018 | Physics and Astronomy

Diving robots find Antarctic winter seas exhale surprising amounts of carbon dioxide

15.08.2018 | Earth Sciences

Early opaque universe linked to galaxy scarcity

15.08.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>