What are facts about placentals?

Placentals are a group of mammals characterized by the presence of a placenta, which allows for a longer gestation period and more developed offspring at birth compared to other mammal groups like marsupials. They are the most diverse group of mammals, including species such as humans, whales, and elephants. Placentals are typically classified into three main groups: Afrotheria, Xenarthra, and Boreoeutheria, each with unique evolutionary adaptations. Their reproductive strategy enables them to provide a stable environment and nutrients to the developing fetus, increasing the chances of survival.