Fossil Representative of Minnesota
Castoroides ohioensis (scientific name) STATUS Unofficial  DESCRIPTION Castoroides ohioensis is an extinct member of the giant beavers that lived in the late Pleistocene epoch, approximately 11,000 to 1.8 million years ago. Giant beavers were enormous members of the order of rodents. Castoroides ohioensis was the largest rodent in North America, growing to the size of a modern black bear. STATE SYMBOL Castoroides ohioensis inhabited all of the United States and Canada, from Yukon to Florida. Giant beavers were, however, most numerous near the Great Lakes, particularly in what are now the states of Indiana, Illinois, and Minnesota. In July 1938, a construction crew building a road in the Mississippi River Gorge in St. Paul, Minnesota, discovered a Castoroides ohioensis skull. This skull now resides at the Science Museum of Minnesota in St. Paul. Legislation that would have made Castoroides ohioensis the Minnesota state fossil was introduced in 1988, but other suggestions for this official symbol were also made. The legislature did not reach an agreement and passed no legislation regarding a state fossil. Although Minnesota does not have an official state fossil, Castoroides ohioensis is important to paleontology and represents the state well. NAME ORIGIN The genus Castoroides was named by American geologist and paleontologist John Wells Foster (1815–1873) in 1838. In 1837, the first specimen of giant beaver was discovered in a peat bog in Ohio; this location led to the prehistoric rodent’s species name, ohioensis. BIOLOGY/ANATOMY Although its form resembles a modern beaver's, Castoroides ohioensis was much larger. This giant prehistoric beaver grew to lengths of over 8 feet (2.4 m) and weighed about 150 to 250 pounds, possibly up to 485 pounds (68 to 220 kg). Since soft tissue does not fossilize, it is not known if Castoroides ohioensis had a flat tail similar to the modern beaver's, but it is thought that the giant beaver’s tail was narrower than its modern counterpart’s. It is known that Castoroides ohioensis had bigger and broader ridged teeth well suited for its plant-based diet. The giant beaver probably built lodges as does the modern beaver, although this is not certain. EVOLUTION/EXTINCTION The first rodents appeared on earth at the end of the Paleocene epoch, approximately 56 to 59 million years ago. Some of the familiar modern rodents, such as the squirrel, evolved as early as the Miocene epoch, about five to 23 million years ago. Castoroides ohioensis appeared in the Pleistocene epoch and became extinct at the end of the last ice age, approximately 10,000 to 12,000 years ago. This was the same time that other Pleistocene megafauna, the mastodons and mammoths, were wiped out. MODERN DISCOVERY The first Castoroides ohioensis fossils were discovered in a peat bog near Nashport, Ohio, in 1837. INTERESTING FACTS A common creation myth of the Mi'kmaq people of Canada includes Glooscap, a mythical culture hero, who turned himself into a giant beaver. The myth states that Glooscap slapped his giant beaver tail in the water, churning up the earth and creating islands in the Bay of Fundy, Nova Scotia. Another Native American belief concerning the giant beaver was held by the now-extinct tribe of Pocumtuck Indians of southern New England. They believed that Sugarloaf Mountain and Pocumtuck Ridge in Massachusetts are the head and body of a giant beaver killed by the spirit Hobomock. A number of versions of this story exist.
	Click to enlarge an image Giant Beaver Skeleton, Field Museum of Natural History, Chicago. Photo by Courtney Horwitz CLASSIFICATION Kingdom Animalia Phylum: Chordata Class: Mammalia Order: Rodentia Family: Castoridae Genus: Castoroides Species: C. Ohioensis
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