Posts Tagged ‘bradyupus ground sloths a sister taxon to all other sloths’

Choloepus Tree Sloths are Closely Related to the Largest Extinct Ground Sloths

January 8, 2015

If I could bring just 1 species of the extinct Pleistocene megafauna back to life, it would be Eremotherium laurillardi, an enormous ground sloth that ranged from tropical South America to the warm coastal regions of southeastern North America during warm climate phases.  Although artists always depict all ground sloths as heavily furred beasts, scientists aren’t so certain about Eremotherium.  Some ground sloths undoubtedly were heavily furred–the mummified remains of 1 species found in a cave did have fur.  But this particular species was found in a colder region of South America.  Tropical species of large ground sloths may have been lightly haired like modern warm climate megafauna such as elephants, rhinos, hippos, and humans.  The difference between Eremotherium and Jefferson’s ground sloth (which ranged as far north as Alaska) might have been comparable to the difference between an African elephant and a woolly mammoth. The megatheridae, the extinct family of really big ground sloths, were closely related to the megalonychidae family which has 1 surviving genera of sloths.  There are 2 species in this genus–Linnaeus’s tree sloth (Choloepus didactlylus) and Hoffman’s tree sloth (C. hoffmanni).  They are mistakenly referred to as 2-toed sloths, but they actually have 2 fingers and 3 toes.  Algae grows on their fur, so they are well camouflaged in the evergreen canopy of tropical forests.  They are also closely related to the dwarf ground sloths that colonized Caribbean Islands and lived there until about 4000 years ago. two-toed sloth pic

Hoffman’s tree sloth is closely related to  the Megatherium and Eremotherium ground sloths.

Oddly enough, anatomical and genetic studies suggest the only other surviving genus of tree sloths is not closely related to Chonoepus sloths or any known species of ground sloth.  The Bradypus genus of tree sloths is considered a “sister taxon” of all other sloths.  Despite the similarity in appearance and habitat adaptations, sloths in the Bradypus genus evolved from a different lineage than Chonoepus sloths.  Both genera evolved their arboreal adaptations independently–an incredible example of convergence.  Most intact jungle ecosystems in South America have 1 species of each genera living in the tree tops.

I believe this is a brown-throated tree sloth.  I found this on google images where it is mistakenly labeled as Hoffman’s ground sloth. It is not closely related to extinct ground sloths and evolved its arboreal habits independently of Choloepus tree sloths.
The Bradypus genus includes 4 species–the brown-throated (Bradypus variegatus), the maned (B. torquatus), the pale-throated (B. tridactylus), and the endangered  pygmy (B. pygmaeus).  Tree sloths mostly eat leaves but also consume fruit, flowers, bark, and rodents.  This is evidence giant ground sloths consumed meat when they could obtain it.  Tree sloths are also known for raiding human latrines where they get minerals from human waste.
Mother tree sloth climbing from a septic tank with a clinging baby sloth.