Originally generic (both spotted and black), then switched to Amur in early 1990s.
Skunk were on the nocturnal portion of the Minnesota Trail (removed 2007), and pika were never on exhibit. Others mentioned were in the Tropics nocturnal section at various points in time, as were quite a few other species (tree shrew, cloud rat, king cobra, etc.).
Original Northern Trail species: Trumpeter Swan, Tiger, Musk Ox, Bactrian Camel, Przewalski's Horse, Moose (yes, that's it). Bison, Pronghorn, Prairie Dog, Coyote (current Takin), Wolf (current Dhole), Caribou, and Red Panda (switched to Arctic Fox, now abandoned) were added early on.
Original Minnesota Trail species. All indoor exhibits (up to the beaver) no longer exist: spotted skunk, Jamaican fruit bat, southern flying squirrel, saw-whet owl, striped skunk, great gray owl, timber rattlesnake, bullsnake, ermine or long-tailed weasel (both held depending on availability), woodchuck, brook trout, turtles, small bird aviary, beaver/waterfowl, MN fish, otter, fisher, porcupine, raven, gray fox, great horned owl, puma, wolverine, lynx.
Original Discovery Trail species: Japanese macaque, (current site of penguins): small herps, MN snakes, small petting zoo mammals (chinchilla/ferret/armadillo/etc.), small parrots/toucans, tidepool invertebrates, lionfish. (current site of Russia's Grizzly coast): domestic ungulates, small petting zoo mammals, New Guinea singing dog, MN waterfowl, variety of small animals in vivaria (generally pet store type but including oddities like Abert's squirrel, mudskipper, pack rat).