Canids are one of ancient groups of predators. They had made great progress at flat landscapes being habitat of numerous herbivores. In Neocene their destiny was changeable: having reached short-term success at plains of ice age, canids had conceded their positions to other groups of predators better adapted for woody districts and bushes. In such conditions canids had kept in very small amount. Besides number of many species had been undermined by people, and they had not gone through climatic cataclysms at the boundary of Holocene and Neocene. But some species managed to survive.
In North America descendants of coyote (Canis latrans) had achieved the great success in struggle for existence. Coyotes had got the big advantage from the neighbourhood with people, having expanded the area and having got rid from wolf, their main competitor. Possible, in first time after human disappearance hybridization of coyote and descendants of domestic dogs took place; it had resulted in enrichment of genetic information of new species becoming ancestors Neocenic of North-American canids. Besides preservation of canids in Neocene was promoted by geography of continent. Prairies formed in “wind shadow” of Rocky Mountains, had continued the existence in Neocene. They became the house for swift-footed herbivorous mammals and “range” for occurrence of new species of canids. Among them two lines separated, leading radically differing habit of life. One line of canids is represented by swift-footed packing predator lupardus, and another one is occupied with massive animal specializing to feeding by large catch – Nearctic hyena-toother. Hyena-toother has occupied a convenient ecological niche of scavenger and large prey hunter. Other representatives of American predators - large cat balam and packing swift-footed canid lupardus catch small and swift-footed animals. But huge peccasons, giant pigs of American prairies, are too large and strong for them. But hyena-toothers are able to overcome such strong herbivore. This predator lives in small packs (up to 10 – 12 individuals) consisting of dominant pair and several subordinated pairs: they succeed to overcome large catch due to harmonious actions. However, they easily snatch catch away at other predators of prairies. This species effectively consumes large catch: after feast of pack of hyena-toothers only tears of skin, jaws and leg bones remain from catch. Other parts of prey are eaten completely. Hyena-toother is a sizable predator (height at a shoulder is more than 1 meter) of massive constitution: the adult animal weighs up to 300 kg. It is similar to large and rather short-legged dog. Shoulders of animal are little bit higher than waist, and back of animal is sloping. Colouring of animals strongly varies: from light grey and even yellowish in southern and southwest areas up to grey with black back and almost completely black at the north. Paws of hyena-toother are rather short, animal can not run fast and for a long time, accelerating maximal speed about 40 kms per hour. Toes of this animal are thick and short, and hyena-toother looks almost plantigrade. Not able to run fast, it swims well and easily walks on marshy ground due to wide feet. Often hyena-toothers preys swift-footed herbivores, pushing them to lakes and swamps and chasing them on fenny ground. Jaws of hyena-toother are adapted to feeding in carrion and crushing bones of large animals: they are short and high, with powerful molars. Canines are big (especially at males: it is an attribute of a sexual dimorphism) and thick, with powerful bases. Tips of canines jut out from closed mouth of predator. But at some external similarity to sabertooth cats it is not their analogue by the habit of prey killing. If sabertooth cats operated by canines as by daggers, hyena-toother operates by them differently: it puts by canines shallow lacerations after which catch bleeds profusely. Eyes of animal are small: sight of hyena-toother is rather weak; it badly distinguishes colors. But the hearing and sense of smell at it are excellently advanced. Also at hyena-toother there is high and wide nasal cavity, and olfactory epithelium forms longitudinal plicas. Ears of animal are big, rounded and mobile. During search of catch hyena-toothers support contact with each other with the help of movements of tail with white hairy brush on the tip. When animals do not hunt, they actively use sounds for communication: hyena-toothers howl, declaring rights of clan to the territory, and also growl and whimper, expressing the mood. Puppies can bark, but adult animals lose this ability. The social habit of life gives big advantages to the hyena-toother in hunting for large herbivores. Animals of different clans develop special tactics of hunting for large animals which transfers from generation to generation. Usually hyena-toothers choose the most perspective catch in herd of herbivores– usually it is young or rather old animal. They rush into herd, separate the planned victim from the common herd and drive it up to exhaustion. Hyena-toothers are not able to run quickly; therefore they drive prey, walking behind it. They have special places for killing catch where animals prefer to make decisive throw and to eat catch. Usually for these purposes places fare chosen, from which it is more convenient to reach lair and cubs. At the period of hunting the young growth is looked after by old animals of clan. Usually young animals start to accompany with adults approximately from four-monthly age. Young males usually remain in parental clan at subordinated roles with strict hierarchy, and females either pass to other clans, or form their own one, which is leading by the male come from other clan. Distribution of hyena-toother in North America to the south is limited by the border of temperate climatic zone. This animal is too massive; that’s why it badly tolerates heat. Therefore at Mexican plateau it is replaced by other American scavenger – marsupial hyaena (Phascohyaena tigrina), the specialized predatory descendant of the opossum.