Botanical Photo

Feature Fossil: Ashfall Fossil Beds State Historical Park

By Gregory Brown

Division of Vertebrate Paleontology

University of Nebraska State Museum

This Feature Fossil is actually a feature site, the Ashfall Fossil Beds State Historical Park in Antelope County, Nebraska. The Park is a joint operation of the University of Nebraska State Museum and the Nebraska Game and Parks Commission. The Museum is responsible for all educational and scientific programs at the Park, as well as for the excavation, preparation and preservation of the fossils themselves.

We've recently added a web version of the Museum Notes issue about the site (Ashfall: Life and Death at a Nebraska Waterhole Ten Million Years Ago). The Game and Parks Commission also maintains a web page describing Ashfall Fossil Beds State Historical Park and includes information about Park facilities and operating schedule.

It has been said, however, that a picture is worth a thousand words. In the case of Ashfall, I'd wager that it's more like ten thousand words. Trying to describe Ashfall is like trying to describe Chocolate Cake...you just have to taste it for yourself. So without further delay, here's a pictorial "taste" of Ashfall . . .




Ashfall Fossil Beds, a Museum locality originally named Poison Ivy Quarry, was discovered in 1971 by paleontologist Mike Voorhies. A scientific excavation was carried out between 1977 and 1979. Over these three field seasons, nearly 100 complete rhinos (of the genus Teleoceros) were discovered and collected, along with dozens of horses, camels, turtles, cranes, and other animals. In the mid 1980's, Mike (shown at left working on the skull of a rhino) and his crew returned to the site to continue explorations and assist with the preliminary plans for a new state park. Our intent this time was not to collect the fossils, but to expose them and leave them in place in the volcanic ash for people to see!
The state of preservation of the skeletons at Ashfall is astounding and provides us with a detailed glimpse of Nebraska 10 million years ago. Aspects of population dynamics, diet, disease processes, and even social behavior are also preserved here as they are at no other known site. At right, preparator Greg Brown does the detailed preparation of a probable mother-baby pair of rhinos (named "Sandy" and "Justin" by the crew) in the Park's Rhino Barn. Preserved in their death positions and touching noses, it is easy to sense the agony they must have felt in their last moments of life. Several other similar associations, many with young rhinos actually in nursing position along side adult females, were excavated from the site in the late 1970's.


Preparator Ellen Stepleton works on the skeleton of an adult female rhino named "Amy". Remarkably, this rhino still carries within it's pelvic cavity the bones of her unborn calf. A closer look also shows that her shoulder has been scavenged by some opportunistic carnivore, and her stomach and mouth contain the remains of her last meal: grass seeds and leaves. Amy is one of more than 25 skeletons (permanent residents!) so far exposed and visible in the Rhino Barn.
Two of Ashfall's 1979 celebrities, complete adult rhinos "Morris" (foreground) and "McGrew" (Background). "Morris" (a male with large tusks and big feet!) and "McGrew" (a female with small tusks and unborn calf) confirm the previously-suspected differences between males and females of this species. Complete skeletons of mammals are rare in the fossil record and add tremendously to our understanding of an animal's anatomy. Catastrophic events that preserve populations or communities of animals are incredibly rare and give paleontologists the equally rare opportunity to do highly detailed studies of such things as population dynamics, sexual dimorphism, variation and behavior.
Within this "Barn" view are the rhinos "Amy" and "Dr. Marie", a small three-toed horse (Pseudhipparion), a small deer-like animal (Longirostromeryx), a camel, and numerous scattered bones. "Dr. Marie" was named after the person who first described the abnormal bone growth associated with severe lung damage or disease. This condition is occasionally found in living animals and humans, but is seldom seen in fossils. Because it is present in every animal found at Ashfall, however, it is likely that the lung damage was caused by breathing large quantities of volcanic ash.
An aerial view of a portion of the Ashfall site. This photo was taken during the Park's development and shows a series of 6-meter sampling grids layed out on the newly-exposed surface of the ash bed. The overburden (sand and sandstone) and the upper 3 to 5 feet of volcanic ash have been removed, leaving the fossils safely buried under another 5 feet of ash. The Rhino Barn (not yet built when this photo was taken) now covers the area at the bottom of the picture. Exploration has indicated that this is a very small portion of the actual bone-bed. Much work remains to be done here, and many more exciting discoveries will be made in the future, perhaps even while you are watching!

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