Museum expert identifies sloth bone from ice age

Sarah Horgen, education coordinator for the University of Iowa Museum of Natural History, cleans mud from a bone of a giant sloth. The museum is located in Macbride Hall on the UI campus in Iowa City. The bones were recently excavated from the Tarkio Valley Sloth Project in southwest Iowa / Photo by Brian Ray, The Gazette

IOWA CITY — The University of Iowa Museum of Natural History’s Tarkio Valley Sloth Project has identified a bone from a type of giant ice age sloth never before recorded in Iowa, called Paramylodon harlani.

Sloth expert Greg McDonald, senior curator of natural history for the National Park Service’s Park Museum Management Program and a consultant on the Tarkio Valley project, identified the 5-inch-long bone as the animal’s fifth metacarpal, which once connected its wrist to its little finger, during a visit to the museum last week.

Southwestern Iowa property owner Bob Athen found the metacarpal nearly two years ago just downstream from the project’s current riverbed excavation site near Shenandoah. It was mistakenly identified as part of a Megalonyx jeffersonii sloth, three of which have been uncovered at the site.

Both Paramylodon and Megalonyx were nearly elephant-sized mammals that became extinct about 12,000 years ago.

The new sloth identification comes on the heels of the discovery April 25 of three more major Megalonyx bones, the first in nearly three years for the project, which began in 2001.

2009 Gazette Communications