From water hole to rhino barn: twelve million years ago, a volcanic ashfall entombed prehistoric animals that roamed what is now Nebraska

Structures that are not helpful to an organism are weeded out by natural selection, because, at minimum, they cost calories to maintain. One of the horse species in particular shows evolution in action. Pliohippus pernix was essentially a one-toed horse, but it retained vestigial side toes that did not provide support. This lineage of horses had likely moved into open grassland to take advantage of new niches, and the side toes were on their way to vanishing.

In 1991 the Ashfall site was opened as a state historical park, operated by the University of Nebraska State Museum and the Nebraska Game and Parks Commission. The park is open seasonally to the public. A structure, aptly named the Rhino Barn, covers part of the fossil bed, where paleontologists have excavated two dozen skeletons and left them for viewing in situ, as a snapshot in time.

Displays and exhibits in the Rhino Barn, the visitor center, and along various trails inform visitors about the history and scientific relevance of the site.

Meanwhile the research continues. Are there even more species of plants or animals whose fossils lie buried in the ash? What happened to the elephants and the carnivores--the saber-toothed cats and those bone crushing dogs--that also inhabited the area? Did they find a way to survive the ancient catastrophe? Or are their skeletons, too, just waiting to be discovered in some unexcavated part of the fossil bed?

SANDY S. MOSEL is air educational programs assistant at the Ashfull Fossil Beds Slaw Historical Park.

For visitor information, contact: Ashfall Fossil Beds State Historical Park 86930 517th Avenue Royal, Nebraska 68773 402-893-2000 www.ashfall.unl.edu

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