Sloths were once the size as elephants

Summary of Sloths are no slouches when it comes to evolution by BioMed Central
according to BioMed Central

Today sloths are known to be very slothful and small, but did you know that their ancestors could be up to the size of elephants. Every million years the elephant sized sloths shrunk down to the size sloths are today. Dr. Anjali Goswami reports “Today's sloths are really the black sheep of the sloth family. If we ignore the fossil record and limit our studies to living sloths, as previous studies have done, there's a good chance that we'll miss out on the real story and maybe underestimate the extraordinarily complex evolution that produced the species that inhabit our world.”

The two existing groups of sloth species bear very little resemblance to some of their extinct relatives. The species Megatherium americium was an elephant-sized ground sloth, which could reach up to four tons. Fossilized track marks suggests they could walk upright on a their hind legs. Eremotherium eomigrans could weigh five tons and their claws grow to a foot long. All but two sloth groups died out around 11,000 years ago now they weigh a maximum of 13 lbs.

BioMed Central. (2014, September 10). Sloths are no slouches when it comes to evolution. ScienceDaily. Retrieved September 11, 2014 from www.sciencedaily.com/releases/2014/09/140910083846