360° Coverage : Rat-size animal may be common ancestor to placental mammals

Rat-size animal may be common ancestor to placental mammals

Scientists believe that a small rat-size animal may be the common ancestors of placental mammals, including humans.

Feb 8 2013, 12:44pm CST | by

Rat-size animal may be common ancestor to placental mammalsO'Leary
Photo Credit: Stony Brook University

LONG ISLAND, N.Y. – Researchers at Stony Brook University here believe they have discovered a rat-size animal that may prove to be a common ancestor to modern day mammals, including humans.

In an article published Thursday in the journal Science, Maureen A. O'Leary, project leader, said that the Protungulatum donnae had many of the anatomical characteristics found in placental mammals that bear their young alive. The living ancestors include 5,400 species of animals ranging from shrews to humans.

The conclusions were reached after scientists determined that a combination of genetic and anatomical data demonstrated that the small mammal evolved from 200,000 to 400,000 years after the planet-wide extinction event at the end of the Cretaceious period. Although some small mammals shared the planet with the last of the dinosaurs, they managed to survive the catastrophe.

By examining fossil evidence and DNA data, the scientists linked the mammal to early placental animals. The Protungulatum species is believed to have had a two-horned uterus and a placenta that provided blood to membranes encapsulating the fetus.

According to researchers, in addition, the study revealed that a branch of the placental mammal tree called Afrotheria, (because these animals—which range from elephants to aardvarks—live in Africa today), actually did not originate on that continent but rather in the Americas.

“Determining how these animals first made it to Africa is now an important research question along with many others that can be addressed using MorphoBank and the phylophenomic tree produced in this study,” said author Fernando Perini, a former postdoctoral fellow at the American Museum of Natural History who is now a professor at the Minas Gerais Federal University in Brazil.

Via Stony Brook University.


<a href="/latest_stories/all/all/19" rel="author">Jeffrey B. Roth</a>
A multi-award winning writer, Jeffrey B. Roth is a well-known investigative reporter, who covers crime, law, politics, sciences, business, medicine, education, history and a wide range of other topics. In 2010, Roth won first place for a new series in the Keystone Press Awards, sponsored by the Pennsylvania Newspaper Association. A published short story writer and poet, Roth is listed in the Locus Index of Science Fiction and Fantasy Authors. Currently, Roth writes for CBS Philadelphia, CBS Baltimore, the Philadelphia Examiner and regional publications, including Carroll Magazine, Carroll Business Quarterly and Hagerstown Magazine to name a few. In the past, Roth, a former crisis intervention counselor and teacher, has written for numerous Pennsylvania newspapers, state and national magazines and the Associated Press. He lives in the foothills of the Appalachian Mountains, west of Gettysburg, Pa.


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