A Vicious Legacy By TrollMans Watch

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Somewhere in the region that will one day become the region of the American Southwest, a pair of Osbornodon stalk a herd of Miohippus grazing in a forest clearing. For the better part of an hour, the two hunters have been slowly inching closer to their quarry, moving behind shrubs and trees to close the distance, and now wait for a suitable animal to wander within range. With powerful jaws and teeth, they'd make quick work of a young Miohippus if they could catch one, but then again catching one is the hardest part. The horses are always alert for nearby danger, as these forests are home to many predators: hyaenodonts, nimravirids, entelodonts, and of course, canids. The dogs wait patiently for one of the more vulnerable among them to slip up and drop their guard just for a second, so they can rush in for the kill.



However, in their intense focus on their hunt, they themselves have fallen for the same mistake that they seek in their own prey. Suddenly, barrelling out of the trees behind them charges out one of the largest and most powerful carnivores of the region, instantly snatching up one of the Osbornodon in its huge beak, as the other flees in confused terror.



For the first time in more than thirty million years, a theropod dinosaur is the apex predator of western North America.



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Early Rupelian (32 MYA), South Dakota



Paracrax gigantea (gigantic near-[curassow])- a species of bathornithid avian known from the early Rupelian of South Dakota, this was likely one of the dominant predators of the region. A large flightless bird, it may have stood over two metres in height, making it comparable in size to the larger species of its southern relatives the terror birds. It not only coexisted with large predatory mammals, but also with other bathornithid species such as Bathornis geographicus, which was almost as large, suggesting a high degree of niche partitioning in this environment, a situation which would be mirrored millions of years later after their extinction when terror birds migrated north; Paracrax may have preferred drier habitats than Bathornis in the diverse environment of the Brule Formation.



Osbornodon sesnoni (Seson's Osborn's tooth)- a species of hesperocyonine canid known from the Oligocene of South Dakota and Oregon. One of the earlier and smaller species in the genus, hesperocyonines were a subgroup of primitive dogs which were an evolutionary dead end, known only from North America and seemingly becoming extinct during the Mid Miocene Disruption. O. sesnoni was about the size of a fox and probably omnivorous, while its later descendant, O. fricki was about the size of a coyote, and the only known member of the group to develop strong carnivorous specializations. Hesperocyonines like O. sesnoni were relatively long-bodied and short legged compared to most modern dog species.



Miohippus obliquidens (slanting tooth small/[Miocene] horse)- a species of three-toed equid known from the Oligocene of the western United States, with its misleading genus name supposedly coming from the mistaken initial belief that it lived during the Miocene, but in reality had become extinct by then. Miohippus evolved from (and for a few million years, coexisted with) the genus Mesohippus and was the genus from which three different branches of horses would arise, forest browsers (Anchitherium), forms that remained small (Archaeohippus), and the modern grazers (Parahippus), which is the only branch that survived into the Holocene. Mesohippus probably fed on both leaves and grass, and was slightly larger than its ancestral genus Mesohippus, with M. obliquidens reaching around thirty kilograms in weight and just over two feet in height at the withers.



two generic passerine birds to fill space

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Published : Mar 18, 2019