Marsupials and placentary mammals are not two levels of development, and two equivalent groups of mammals. Marsupials do not have attributes because of which they can be counted “lower” ones. Presence of brooding pouch and way of posterity bearing has imposed some restrictions to adaptive opportunities of marsupials: among them forms constantly or the most part of time living in water basically can not appear. But in ground habitats marsupial mammals rather successfully can compete with placentary ones. Isolation on southern continents obviously has not was of use for them: developing “using own sources” and being out of competition, marsupials lost in ingenuity level to the placentary contemporaries from other continents. After to South America and Australia placentary mammals have got, the significant part of marsupials had lost struggle for existence and had disappeared from Earth’s face. But extinction of plenty of mammal species in late Holocene and early Neocene had balanced chances of marsupials and placentals in the further existence. In South America some new kinds of marsupials successfully competing with placental ones had appeared. Among them representatives of American marten opossums family, predators of woods and mountains, are especially remarkable. They had descend from American opossums (Didelphidae), but evolution has perfected their predating abilities, having made these animals one of the most successful group of local predators. In forest canopy of the Amason region, stretched to many thousand square kilometers, one of representatives of this family, ipochereu, or Amazon marsupial marten lives (Ipochereu is a name of marten, the hero of fairy tales of one Indian tribe of Amason region). By constitution ipochereu resembles the true marten, but it differs from them in larger size: length of body is about 70 cm (tail is about 1 meter long), height at a shoulderis about 30 cm. The long body and short paws with tenacious sharp claws are adaptation features for life in rich branches. Amazon marsupial marten differs in big flexibility and mobility: this predator easily can run across the rivers along thin liana at 30-meter height. Due to tenacious claws this animal moves on tree trunks easily as if squirrel. The tail of this marsupial marten is not prehensile, but during jumps from tree to tree it serves as the balance weight. Colouring of wool of Amazon marsupial marten is spotty - on grayish-brown background there are longitudinal lines of small white spots merging on back to faltering strips. Stomach is white. Obverse part of skull is short, but jaws are wide and strong. Brain cavity of skull is long and low. This predator kills catch (large forest rodents, birds and reptiles) by strong bite to backbone or in basis of skull. Eye-sockets are wide, sight is substantially binocular due to what the animal can precisely estimate distance before jump. Ears are short and rounded. On muzzle long whiskers grow. As the majority of large predators, Amazon marsupial marten is solitary animal. Each animal occupies extensive territory - about 10 square kilometers. Borders of territory are marked by urine and areas of toren bark (as bears in Holocene acted), and carefully protected. Only males during breeding season come to the territory of females for pairing. Amazon marsupial marten has two peaks of activity: in the morning (from dawn up to hottest time of day) and in the evening up to sunset. In the afternoon in heat the animal has a rest in shadow or hides in tree-trunk hollow. Sometimes Amazon marsupial marten goes down to the ground and sleeps in shadow under tree roots. On the ground this predator finds food – carrion, eggs of turtles and other reptiles. Sometimes ipochereu catches fish and crabs in shallow streams (especially frequently it makes it in mountain areas). At ipochereu the expressed seasonal prevalence in breeding is not present, but in mountains or in the south of area cubs are born in early spring, and even at the end of winter. The pouch at this species of animals represents the horseshoe-like plica of skin inverted by the ends to tail. Up to the moment of posterity birth it is stretched, providing preservation of posterity and when cubs leave it, pouch is compressed again. In pack there are up to 5 cubs born underdeveloped as at all marsupials. They stay in pouch within three months, eating milk and developing. Then the female some time carries them on back (the relationship with opossums has an effect), but at this species similar feature gradually passes to past. In mountains some females may at once leave rather developed cubs in shelter (similarly to Australian predatory marsupial): cubs sitting on back simply prevent to hunt. Besides sometimes during catch chasing the cub simply can fall down from mother’s back and injure itself up to death. Because of it before independence only 1 - 2 cubs from pack survive. At the age of 5 months they start to hunt with mother, and completely pass to meat feeding. At this time the female is ready to rear posterity once again. At the age of seven month young animals already are completely independent, and the female already bears the next pack in brooding pouch.