Sentences with phrase «not placental mammals»
According to scientists, retroviruses probably developed in marine vertebrates, not placental mammals.
https://www.seeker.com/ Not exact matches
Because so little is known about Gondwanan mammals, Krause is wary of dismissing Rich's interpretation «just because we don't expect, based on current knowledge of early mammalian evolution on Gondwana, to see a placental mammal in the Early Cretaceous of Australia.»
«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.
These inconsistencies can be resolved by the simple hypothesis that placental mammals originated in Gondwanaland, not Laurasia, says mammalogist Tim Flannery, director of the South Australia Museum in Adelaide.
Marsupials do not show the spectacular diversity of placental mammals.
They turned up at sites on landmasses that once belonged to Gondwanaland — sites where they should not be if placental mammals arose in the northern landmass of Laurasia.
In the 14 December issue of Science, the researchers report that that placental mammals all trace their roots to what is now Africa, not to an ancient northern landmass.
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.
For one, placental mammals do not neatly divide into the four categories that researchers typically group them into.
According to the new tree, the first placental mammals appeared around 65 million years ago, not 100 million years ago or more, as some molecular data have suggested.
More recent genetic analysis — not yet universally accepted — places bats in the superorder Laurasiatheria, with a diverse bunch of other placental mammals including whales, dogs and giraffes.