Marsupial Fossils: Kangaroos, Koalas, Marsupial Lions & kin

        Marsupials are a large infraorder of mammals that have evolved into a variety of well-known forms, including the bear-like koala, the partially bipedal, hopping kangaroos, and even extinct predators like the Marsupial Lion and Tasmanian Tiger (AKA Tasmanian Wolf or Thylacine). Genetic evidence suggests that Marsupials split from a common ancestor with their closest relatives, the placental mammals, in the Jurassic period approximately 180-160 million years ago. The oldest confirmed Marsupial fossils are that of a small, shrew-like creature found in China called Sinodelphys  (dating to the Cretaceous period, approximately 125 million years ago). Marsupials have a rich migratory prehistory, spreading from Eurasia to North America, to South America, to Antarctica (still connected to South America until around 35 million years ago), and finally to Australia in the Eocene epoch, approximately 50 million years ago. Today, Marsupials exist largely in Australia and various parts of Southeast Asia (such as New Guinea), with some species in South America, and one lone species in North America (the Virginia opossum). The main difference between placentals and marsupials is the incredible means by which they give birth. As opposed to birthing a fully developed newborn, Marsupials will give an early birth of about 4-5 months to their joey (the name for an infant marsupial), which then has to climb up to its mother's teats that are located in a pouch on her abdomen, where the joey further develops. In this state, the joey is blind, furless, and about the size of a jellybean. Several months later, the joey is fully developed and will come out of its mother's pouch, only to return for sleep or safety until it has matured.