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University of Iowa News Release

Oct. 20, 2003

(Photos: Left, Bob Athen with part of the giant sloth skeleton he found in southwestern Iowa; Right, more bones discovered by Bob and Sonia Athen.)

UI Museum Of Natural History, Department Of Geoscience Excavate Giant Sloth Bones

The discovery of giant sloth bones in southwestern Iowa and their relocation to the University of Iowa Museum of Natural History will provide new evidence about how sloths lived in Iowa during the Ice Ages as well as result in a new museum display, according to museum coordinator David Brenzel.

"When the dig is complete sometime next year, we will display the giant sloth skeleton in the museum," he said, "perhaps next to 'Rusty,' our Iowa Hall model of a giant ice age sloth. We may need to rearrange a portion of the geology section in order to accommodate it."

Discovered in the summer of 2002 near the town of Shenandoah in southwest Iowa, the bones immediately caught the eye of discoverers and landowners Bob and Sonia Athen. They pulled fragments from a creek bed and began gluing them together at home, but it wasn't until they brought the bones to the UI that they learned what they had found. Contacted by the Athens, Curator of Paleontology Julie Golden called Holmes Semken, emeritus professor of geoscience in the College of Liberal Arts and Sciences, who immediately recognized them as the remains of a giant sloth. The sloth was a furry, plant-eating mammal that weighed 2-3 tons and lived during the Pleistocene Epoch, a time when glaciers covered much of Iowa, until becoming extinct some 9,500 years ago.

"Sloths were so massive -- ranking in size between a bison and a small Indian elephant -- that their bones are unlike anything else," Semken said. "Anytime you find a complete or largely complete specimen, it's of scientific significance. This find is one of a few in North America and a first-of-its-kind find for the state of Iowa."

So far, the team of more than a dozen scientists, museum volunteers and the Athens have unearthed a significant portion of the sloth skeleton, including the chest with the shoulder blades and collar bones, atlas (the topmost neck vertebra), a thigh and a tail vertebra. Finding both large and small bones in one place has raised hopes that most of the skeleton will eventually be recovered. "That tells me the whole animal was there at the end of the Pleistocene and that it was not reworked by stream action at least until the 1993 Flood," said Semken, who, with Brenzel, plans to lead museum and geoscience volunteers on numerous trips to the site in 2004 in order to complete the dig.

He noted that other geologists are examining the clay surrounding the sloth skeleton for pollen, plant fragments and other animals that existed during the period. They hope the information will help them to construct an accurate assessment of the environment at the time of death for museum display. In the meantime, Semken and his colleagues will return to the site this fall to collect geologic data that will help them to plan next year's digs on both banks of the creek (the opposite bank is owned by Dean and Loreta Tiemann of Lincoln, Neb.) and to speculate where on the creek bed the remainder of the skeleton is concealed.

Brenzel said that the scope of the museum display will depend upon the success of any fund-raising efforts, as well as the volume of bones ultimately recovered from the dig site. "The question now is, 'Where is the rest of the sloth skeleton?' he said. "All of us, including the Athens and the Tiemanns, would like to display it in the museum as soon as possible."

Scenes of the excavation will soon be available at both the Museum of Natural History ( and department of geoscience ( web sites.

STORY SOURCE: University of Iowa News Services, 300 Plaza Centre One, Suite 371, Iowa City, Iowa 52242-2500.

CONTACTS: Gary Galluzzo, 319-384-0009,