A study, conducted by Maureen O'Leary, a paleontologist at Stony Brook University in New York, and her research team, concluded that the ancestor of all placental mammals evolved “less than 400,000 years after the mass extinctions that wiped out the dinosaurs.” The groundbreaking study's findings were published on September 26 in Proceedings of the National Academy of Sciences.
Placental mammals are commonly known as those that give birth and nourish their embryos throughout gestation via the placenta which is usually attached to the wall of the mother's uterus. A total of more than 5000 species exist within the placental mammal group from the massive blue whale to the bumblebee bat which is known to be tiny. Marsupials, on the other hand, are different as they have a very short-lived placenta during gestation.
The hypothetical creature’s fossil records infer that it was probably a small-sized mammal who ate insects for survival and climbed trees. It weighed approximately around 6 and 245 grams—” somewhere between a small shrew and a mid-sized rat”, a report on Science.com quoted. The creature featured a furry coat, and a long thin tail and gave birth to a single offspring. It also had a complex brain with the ability to interpret smells and a bundle of nerve fibers that connects the left and right hemispheres of the brain.
The new study, conducted by O'Leary, used genetic information to “arrange the branches on the family tree of placental mammals”. The team of researchers, however, didn’t end up using a molecular clock inferred from rates of mutation to determine when the various branches first appeared, as told to Science.com. She went on to explain that statistical methods that help researchers determine the length of those branches as well as their arrangement “will certainly shed more light on mammalian evolution.”