THE EXTINCTION SERIES: GIANT SLOTH
- Apr 12, 2019
- 3 min read
Giant ground sloths were large, lumbering beasts that lived in the Americas during the Ice Age. They were directly related to today's modern sloths. They were also distantly related to anteaters and armadillos.
The six modern species of sloths are all arboreal, so they are called tree sloths. These sloths are small-bodied and weigh less than 20 pounds. Many of their extinct relatives were much larger and lived on the ground. Because of this, they are referred to as ground sloths.
One species of ground sloth is named after Thomas Jefferson. Jefferson first thought the bones belonged to a large lion and called it the "Great Claw," or Megalonyx, according to the Thomas Jefferson Encyclopedia. In 1797, as he was preparing a paper on the find for the American Philosophical Society, he saw an engraving of a sloth skeleton and realized that his fossil was similar and that his classification was wrong. Later, Jefferson was credited with discovering the extinct sloth, which was named Megalonyx jeffersonii.
Megalonyx jeffersonii was the largest of the ground sloths in family Megalonychidae, reaching the size of an African elephant when fully grown. Megalonyx sloths grew to around 3 meters long and weighed up to 1,000 kilograms, according to the San Diego Zoo.
Giant ground sloths evolved in South America around 35 million years ago. Around 8 million years ago, they migrated into North America, according to the San Diego Natural History Museum.
Giant ground sloths preferred forests along rivers or lakes, but they also lived during the Pleistocene period, also known as the Great Ice Age. At its peak, as much as 30 percent of the Earth's surface was covered by glaciers and parts of the northern oceans were frozen, according to the San Diego Natural History Museum. This made for a very cold environment that few animals could endure.
By the end of the Great Ice Age, around 11,700 years ago, many believe that the giant ground sloths had become extinct. Some argue that they were around for many more thousands of years, though, surviving on islands in the Caribbean.
Ground sloths were herbivores, meaning they ate vegetation. Their peg-like teeth were ideal for this diet, but they also had other body parts that played a large part in their meals. They had long curved claws , measuring upto 40 cm in length, likely an adaptation for foraging for grabbing branches and stripping foliage from tree limbs, as well as for protection from predators. They also had tough skin and protective cartilages on their necks, shoulders and back which were areas predators would target.
Their hind foot structure and posture of the ground sloths also helped it with meal time. They likely relied on their robust hind feet, in combination with a stout tail, to support their massive bodies when rearing on their hindquarters to reach high into trees for forage.
Megalonyx fossils have been recovered from about 150 sites across North America, according to the Illinois State Museum. Some have been found as far north as Alaska and the Northwest Territories of Canada. They have also been found in California, Arizona and New Mexico, as well as northern Mexico. In the Midwest, most of them have been found in caves, including sites in Missouri, Minnesota, Illinois, Ohio, Kentucky and Tennessee.
The exact reason for their disappearance is yet not known. However, humans were contemporary to these creatures and are thought to be their primary enemies and predators, responsible for their extinction about 10,000 years ago by hunting them down for food. Another theory is that they were highly susceptible to the climatic changes which reduced the vegetation they fed on thus many had to migrate to areas outside their natural habitat.
Watch the short video on ground sloths to learn more interesting facts.
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