Sentences with phrase «of placental mammals»

In an attempt to determine whether it was a placental mammal, the scientists constructed a tree charting the evolution of placental mammals beginning well in the Cretaceous.

«When I took the remaining set of calibrations, the major diversification of placental mammals coincided with the extinction of dinosaurs,» Dr Phillips said.

Earth's four groups of placental mammals likely arose from an ancient southern continent.

«It now appears that the major diversification of placental mammals closely followed the extinction of dinosaurs 66 million years ago, an event that would have opened up ecological space for mammals to evolve into.»

Senior author, Professor Anjali Goswami (UCL Genetics, Evolution & Environment and UCL Earth Sciences), said: «Our findings refute those of other studies which overlooked the fossils of placental mammals present around the last mass extinction.

«The discovery of Eritherium supports an explosive radiation of placental mammals» in that period, he says.

To figure out how chromosomes of placental mammals have changed over time, researchers need to know what those early eutherians started with.

A new digital reconstruction of the chromosomes of the ancestor of all placental mammals reveals that these tightly packed structures of DNA and proteins have become scrambled over time — a finding that may help pinpoint possible problem sites in our genomes that underlie cancer and other disease.

«Almost undoubtedly you would need some intermediate land masses to show the presence of placental mammals and right now we don't have those records,» he admits.

Instead, it seemed to be the jaw of a placental mammal — the group that includes horses, cats, bats, whales and people.

J. David Archibald, an evolutionary biologist at San Diego State University, praised the new study as being the most comprehensive analysis yet into the evolution of placental mammals based on the shapes and forms of fossils.

Marsupials do not show the spectacular diversity of placental mammals.

Although the Argentine team suspects that the bone came from an egg - laying mammal, other paleontologists believe it shows traits of a placental mammal.

To find out how, Chavan compared implantation in the opossum with that in a range of placental mammals: rabbits, armadillos, and hyraxes, a 3 - kilogram rodentlike mammal that's closely related to elephants.

250 - year - old statistical technique has prompted researchers to rewrite the evolutionary history of placental mammals, which include humans and all other mammals that give birth to live, fully developed young.

But Stephen O'Brien, an evolutionary biologist with the National Cancer Institute in Frederick, Maryland, is not convinced the work tells the true story of placental mammals.

A unique feature of placental mammals, extra-embryonic tissues such as the placenta and yolk sac are vital for nutrient and waste exchange between the fetus and mother.

Control of these genes» expression in the mammary bud has thus evolved thanks to the hijacking of this pre-existing regulatory module, thereby explaining the later arrival of such a structure, and thus of the placental mammals and the marsupials.

Placental mammal fossils from this period have been previously overlooked as they were hard to place in the mammal tree of life because they lack many features that help to classify the living groups of placental mammals.

The team found the speed of evolution of placental mammals — a group that today includes nearly 5000 species including humans — was constant before the extinction event but exploded after, resulting in the varied groups of mammals we see today.

A research team found the speed of evolution of placental mammals — a group that today includes nearly 5000 species including humans — was constant before the extinction event but exploded after, resulting in the varied groups of mammals we see today.

Now sequence comparisons with rats, mice and dogs show that the X chromosome seems to have changed little since the evolution of placental mammals, supporting the idea that once genes are transferred to X, they stay there.

The Natural Environment Research Council - funded research, published in the Biological Journal of the Linnean Society, studied the early evolution of placental mammals, the group including elephants, sloths, cats, dolphins and humans.

This makes them part of Laurasiatheria, one of the major groups of placental mammals.