Speaking of Nebraska fauna, that is animals, one can start a few million years ago. According to science writer Bob Strauss, (The Dinosaurs and Prehistoric Animals of Nebraska).
“Somewhat surprisingly, given its proximity to dinosaur-rich Utah and South Dakota, no dinosaurs have ever been discovered in Nebraska — though there’s no doubt that hadrosaurs, raptors, and tyrannosaurs roamed this state during the later Mesozoic Era. Making up for this shortfall, though, Nebraska is famous for the diversity of its mammalian life during the Cenozoic Era (a long time ago). During the Cenozoic Era Nebraska fauna included camels, horses, dogs, rhinos, mammoths, mastodons, beavers and the infamous “terrible pig”.
Bob Straus again: “Formerly known by the more evocative name Dinohyus — Greek for “terrible pig” — the 12-foot-long, one-ton Daeodon resembled a hippopotamus more than it did a modern porker. Like most of Nebraska’s fossil mammals, Daeodon prospered during the Miocene epoch (very long time ago), from about 23 to 5 million years ago. And like virtually all of Nebraska’s mammalian megafauna, Daeodon, and other ancestral pigs eventually vanished from North America, only to be reintroduced thousands of years later by European settlers.”
Coming to more recent times, say from a few thousand years ago to present day Nebraska, the University of Nebraska reports that Nebraska has an abundance of diverse animal life. This animal life includes 80 species of mammals, 11 species of frogs and toads, 3 species of salamanders, 9 species of turtles, 10 species of lizards, 30 species of snakes, 400 species of birds (including 6 endangered species such as the Whooping Crane), 206 species of butterflies, and 22 different families of fish. This accounting does not include the very important presence of insects (bees for examples) and microbes (such as nitrogen fixing Rhizobium) all very important and studied by the University of Nebraska. The list of Nebraska fauna can be found on the University of Nebraska’s website here.