I'm a big fan of paleontology, and while dinosaurs have to be my first true paleontological love (of course) not far behind them are the therapsid and thecodont assemblages of the late Permian and Triassic--prior to the dominance of the dinosaurs--and the late Age of the Mammals: the Pleistocene megafaunas that we mostly just barely missed seeing. Today, only Africa (and to a slightly lesser extent Asia) contain full, robust mammalian megafaunas. Those of Europe, North America, South America, and Australia are impoverished. (And Antarctica hasn't had a robust mammalian megafauna since at least the Grand Coupure, or Eocene-Oligocene Extinction Event of 34 million years ago.)
My initial thought, then, was that the DARK•HERITAGE would feature a North American Pleistocene fauna. This is pretty much the same as the current fauna, but it adds a number of other players--big lions, sabertooths, mastodons and mammoths (mostly non-woolly, because I'm doing a more temperate climate), giant bears and beavers, giant camels and llama-like creatures, wild horses of various species, etc.
I decided to mix this up just a bit, although the details are somewhat esoteric and probably not of interest to many. But they were to me. I decided to use "bone-dogs" instead of dire wolves, because I thought they'd be a little more interesting and exotic. "Bone-dogs" are what I call Borophagus diversidens, often called "bone-crushing dogs" because of their hyena-like jaw morphology. These poor guys have unfairly been labeled scavengers, but given the numbers of them, that's seems fairly ridiculous. Given the fact that hyenas have also been conclusively demonstrated, despite long-held prejudices to the contrary, to be successful active hunters who are often hanging around hoping to scavenge their own kills after lions have bullied them away from it, the idea of bone-dogs being obligate scavengers, or even primarily scavengers, seems intellectually bankrupt.
I also referred to hyenas in Kurushat earlier, when it was more overtly D&D-like, because it included gnolls as well. This led me to decide that the southern shores of the Mezzovian Sea have a European-Central Asian Pleistocene megafauna, including cave hyenas, Elasmotherium and other hairy rhinos, cave lions, etc. It isn't really terribly different from that of North America if you pave over minor differences--cave lions vs. American lions, tarpans vs. Equus scotti and other species of American horse, Columbian mammoths vs. steppe mammoths or straight-tusked elephants, ancient bison vs. steppe bison, red deer vs. elk, etc. There are a few unique indicators, like hyenas and rhinos to Europe, and ground sloths, glyptodonts and various camelids to North America. And besides, who really cares about the difference between a cave lion and an American cave lion anyway?
But lately, I've been somewhat obsessed with Patagonia. I'm now putting it high on my list of desirable hikes, and I especially like that their hiking season is directly opposite that of North American mountains (the same is also true of the Southern Alps of New Zealand, by the way.) It occurs to me, however, that I can get this fairly quickly in DARK•HERITAGE by focusing more on the flora than the fauna. Lenga and ñirre trees instead of pines--maybe even some monkey puzzle trees instead of stuff like ponderosa or white pines and aspens or junipers. Most of the animals of Patagonia, actually had close analogs during the Pleistocene in North America; in fact, most of them originally came from North America during the Great American Interchange. There were some specific Pleistocene South American animals--like toxodons and Macrauchenia. Gomphotheres and giant sloths are similar enough to mastodons and North American giant sloths. Tapirs, guanacos and llamas are all animals that had Pleistocene North American counterparts. A few flightless birds, like rheas, are about the only significant orphans that can be found in Patagonia but don't have analogs in North America, but I can add them if I want them, or not if I don't.
Why bother? Eh. It's just a minor detail. Windswept lenga forests that turn orange and then red in the fall as opposed to conifer clad mountains aren't all that different. Pampas and Great Plains--well, other than the rheas, what's the difference? It's a bit of color that most people won't even notice. But I would.