Date of this Version
Johnsgard, "The Age of Birds in Nebraska" in Nebraska Bird Review (March 1999) 67(1).
Let each mile of highway I-80 represent a million years. That way, 1/2 mile represents 500,000 years, 1/10 mile = 100,000 years, 1/100 mile (52 feet) = 10,000 years; 1/1000 mile (5.2 feet) = 1,000 years, and 6 inches = 100 years. A decade (ten years) equals about a half-inch. It is 450 miles from the 60th St. on-ramp to I-80 in Omaha to the westernmost exit at the Wyoming border. These 450 million years encompass most of the time that evidence of life has been found on earth, but the earth itself is more than four billion years old, or ten times older than the time scale described here.
Some 450 million years ago, as we join the I-80 in Omaha, we are in the middle of the Paleozoic era, when Nebraska was submerged in a great inland sea, and the animals present would be mostly corals, sponges, and mollusks, plus a few primitive fishes, such as sharks. Evidence of this early life can be found in limestone outcrops such as those near Weeping Water in southeastern Nebraska. There were no birds or mammals to be seen.
As we drive the 50 miles to Lincoln, we have covered 50 million years to 400 million years ago, and are entering the Devonian era. We must drive all the way to Kearney, some 270 million years ago, before the last remnants of the Permian Sea have retreated and left us on dry land. To reach the great age of dinosaurs, the Mesozoic, which started some 220 million years ago, we must get to Cozad. From there to Ogallala, the distance representing the peak of the dinosaur era, there is no clear geologic record in Nebraska, but dinosaur fossils in eastern Wyoming and western South Dakota tell us of these great beasts. The first known bird, Archaeopteryx, took flight during the middle of the Mesozoic, sharing the sky with flying reptiles, about 140 million years ago. By then a few primitive mammalian groups were also already present. The last great period of the Mesozoic, the Cretaceous period, covers the distance from Ogallala to Sydney. It is a time when Nebraska was again covered by shallow seas, with long-necked plesiosaurs swimming through the waters and sometimes rivaling the largest dinosaurs in size. There were also mosasaurs, sea-going lizards with large crushing jaws, eating sharks and bony fishes. Loon-sized but flightless fish-eating birds, Hesperornis and its kin, swam through the shallow seas of what is now Kansas and probably also Nebraska. Above the seas, tern-like birds (Ichthyornis, Apatomis) fished in the shallows.