Sunday, May 20, 2012

GROUND SLOTH FAMILY: Stories of the Imagination

One of the poster Mammals of prehistory was the massive Megatherium americanum (Giant Ground Sloth) of the extinct Ground Sloth Family.  This huge Mammal stood at twenty feet (six meters) and weighed about 4.4 tons (4 metric tons). As big as a modern Elephant, Megatherium was one of the largest Mammals ever to walk on land.  Moreover, this Ground Sloth ate over seventy different types of plants and as well as scavenged for meat.

            The diverse Family of Ground Sloths includes more than just Giant Ground Sloth.  This extinct Family as well as the Family of Modern Sloths belongs to the Order of Xenarthra (meaning “without teeth”).  Modern Two-toed Sloths (Choloepidae) evolved from the Flat-footed Ground Sloths (Megalonychidae).  Meanwhile, Three-toed Sloths (Bradypodidae) arose from the Browsing Ground Sloths (Megatheriidae).

            The Flat-footed Family of Ground Sloths walked on the bottoms of their feet instead of on their sides like other Sloths.  The Browsing Ground Sloths featured both the Giant Ground Sloths and the smaller Ground Sloths such as Shasta Ground Sloth (Nothrotheriops shastensis) of North America.  Meanwhile, Grazing Ground Sloths (Mylodontidae) such as Harlan’s Ground Sloth (Paramylodon harlani) lived in small herds out in open country.

            Although many species of Ground Sloths became large, some still remained as small as cats.  These Ground Sloths lived on the islands in the Caribbean Sea until the mid-1500s.  They, like every other Ground Sloth, had sharp claws and interlocking small boney plates under their skin.  Serving as chain mail, these plates made Ground Sloths virtually indestructible.

            By sparking people’s imaginations, Ground Sloths prompted humans to want to learn more about the world around them.  First discovered in Argentina in 1787, the fossils of Megatherium shocked people.  Her huge size created a world-wide sensation since nobody thought that animals could become that big.  Megatherium challenged people of that time to make sense of the concept of extinct and giant Animals. 

Meanwhile, the bones of Jefferson’s Ground Sloth (Megalonyx jeffersonii) were found in a cave in West Virginia (U.S.).  After receiving the bones of this Ground Sloth, Thomas Jefferson put them on display at the White House and later in his home at Monticello.  His intense curiosity about the life of this particular species of Ground Sloth prompted others to begin to study paleontology in earnest. (Megalonyx jeffersonii was named for him.)

Originating in Patagonia, Ground Sloths went to North America during the Great American Faunal Interchange (about eight million years ago (mya) to three mya).  They rafted and island hopped from South America to the north, traveling as far as the Yukon Territory.  Meanwhile, the last of the Ground Sloths went extinct on the Caribbean islands during the 1500s.  However there are rumors that Ground Sloths, now known as Mapinguari by the local people, still roam the Amazon River Basin.

Ground Sloths inspire us to imagine what could be from what we discover.  They invite us to expand the parameters of our world.  We may tell wild stories about Them such as prehistoric peoples once keeping Ground Sloths for food.  However like Jefferson who first thought that they were carnivores, we can change our minds when we uncover more information.  By surprising us around every bend in the road, Ground Sloths encouraged our stories of imagination.  Perhaps once we expand our imaginations further, we may see Ground Sloth in the Amazon as Mapinguari.

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