Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Guinea-zilla? World’s largest rodent identified as ancient sibling to guinea pigs

19.09.2003


Roughly the size of a buffalo, a giant rodent that roamed the banks of an ancient Venezuelan river some 8 million years ago, dining on sea grass and dodging crocodiles, was an evolutionary sibling to modern-day guinea pigs.

The largest rodent that ever lived, Phoberomys pattersoni, weighed about 1,545 pounds (700 kilograms) - more than 10 times the size of today’s rodent heavyweight, the 110-pound (50 kilograms) capybara.

"Imagine a weird guinea pig, but huge, with a long tail for balancing on its hind legs and continuously growing teeth," said Marcelo R. Sánchez-Villagra of Germany’s University of Tübingen. "It was semi-aquatic, like the capybara, and probably foraged along a riverbank."



The ancient creature’s fossilized remains -- described in the 19 September, 2003 issue of Science, published by AAAS, the science society -- offer rare, tantalizing new clues to the Upper Miocene period in northwestern Venezuela.

Discovered in a now-arid region 250 miles west of Caracas, in the town of Urumaco, the fossil and associated plant evidence suggest a lush, tropical landscape, rich with super-sized turtles, catfish and crocodiles. The Science paper thus seems to reinforce the theory that a massive river called the Paleo-Orinoco-Amazon once flowed parallel to the Andes mountain range through Urumaco, in the Falcon State, northeast to the Caribbean Sea.

"The northern region of Venezuela holds the key to many mysteries of paleontology and animal evolution," said Sánchez-Villagra. "Yet, we have known very little about this area because regions covered with vegetation are not the best place to look for fossils. Most of the fossil evidence has been found in southern South America. With this work, we are taking steps toward broadening our knowledge of South America as a whole."

Why don’t buffalo-sized rats roam the Earth today? And, why did Phoberomys pattersoni reach such massive proportions?

R. McNeill Alexander of the University of Leeds, author of a related Perspectives essay in Science, noted the relationship between body posture and the size of various animals: Tiny mice, for instance, crouch on very bent legs, whereas elephants tend to keep their legs relatively straight. "The giant rodent fossil raises wonderful questions about the constraints of evolution on size," Alexander said.

The cause of the demise of Phoberomys remains a mystery. But, Alexander pointed out that small mammals such as rodents typically escape predators by burrowing into a refuge. "Large mammals, too big to burrow, can generally escape only by running," he explained. "Ungulates -- with their long legs, light hooves and long elastic tendons -- seem best for that. Would large rodents generally be too slow to be successful?"

Dubbed "Goya," the 90-percent-complete fossil of Phoberomys pattersoni was trapped within sedimentary layers of brown shales and coal, within the Urumaco Formation. It was discovered by a research team under the direction of Orangel Aguilera of Venezuela’s Universidad Nacional Experimental Francisco de Miranda, co-author of the Science paper. The Science team also includes Inés Horovitz, now at the University of California in Los Angeles.

Researchers found the fossil in mid-May 2000, but never specifically classified it, until now. Scientists had speculated that it might be related to various other rodents -- either chinchillas, viscachas or pakaranas. By examining the Goya fossil, together with a second specimen offering more complete skull evidence, the authors were able to identify Phoberomys pattersoni as a sibling to the pakarana Dinomys -- a close relative of the guinea pig (Cavia porcella).

Some 9 feet long (3 meters) and 4.2 feet tall (1.3 meters), Phoberomys pattersoni had long teeth revealing an abrasive diet, perhaps of grasses from brackish water. Its hind quarters and rear legs were much larger and more powerful than its smaller forelimbs, much like a guinea pig. Yet, today’s guinea pigs weigh about 2.2 pounds (1 kilogram).

Both creatures belong to a diverse radiation of South American rodents called Caviomorpha. Today, this group of rodents ranges in size from 8 ounces, or one-half pound (200 grams) to 110 pounds (50 kilograms).

Andrew Sugden, an evolutionary biology expert and Science International’s Managing Editor, described the research as a milestone within the field: "At a stroke, this giant rodent more than doubles the size range of this remarkable family of animals and provides fascinating new insights into life some 8 million years ago," he said.

Until the emergence of a land-bridge (the Panamanian isthmus) connecting Central and South America some 3 million years ago, South America had been an island for tens of millions of years, Sugden explained. South American animals thus managed to evolve in relative isolation, and the continent became home to giant representatives of a number of mammalian groups, some of which survived until the arrival of humans.

Research in Venezuela was partially supported by the National Geographic Society and the University of Tübingen. The Smithsonian Tropical Research Institute and the Universidad Nacional Experimental Francisco de Miranda (UNEFM) supported Aguilera’s field and laboratory work.


###
Founded in 1848, the American Association for the Advancement of Science (AAAS) has worked to advance science for human well-being through its projects, programs, and publications, in the areas of science policy, science education and international scientific cooperation. AAAS and its journal, Science, report nearly 140,000 individual and institutional subscribers, plus 272 affiliated organizations in more than 130 countries, serving a total of 10 million individuals. Thus, AAAS is the world’s largest general federation of scientists. Science is an editorially independent, multidisciplinary, peer-reviewed weekly that ranks among the world’s most prestigious scientific journals. A component of Science’s career mentoring Web site, Next Wave, the Postdoc Network (http://nextwave.sciencemag.org/pdn) provides a forum for people interested in improving the experience of being a postdoc. AAAS also administers EurekAlert! http://www.eurekalert.org, the online news service, featuring the latest discoveries in science and technology.

Ginger Pinholster | EurekAlert!
Further information:
http://www.aaas.org/
http://nextwave.sciencemag.org/pdn

More articles from Life Sciences:

nachricht Topologische Quantenchemie
21.07.2017 | Max-Planck-Institut für Chemische Physik fester Stoffe

nachricht Topological Quantum Chemistry
21.07.2017 | Max-Planck-Institut für Chemische Physik fester Stoffe

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

Im Focus: Laser-cooled ions contribute to better understanding of friction

Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision

Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

NASA looks to solar eclipse to help understand Earth's energy system

21.07.2017 | Earth Sciences

Stanford researchers develop a new type of soft, growing robot

21.07.2017 | Power and Electrical Engineering

Vortex photons from electrons in circular motion

21.07.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>