Complex sentence: Sloths belong to the superorder Xenarthra, a group of placental mammals that evolved in South America around 60 million years ago, although at least one study found that xenarthrans broke off from other placental mammals around 100 Mya.
Split into simpler sentences: Sloths belong to the superorder "Xenarthra", a group of placental mammals that's believed to have evolved in the continent of South America around 60 million years ago. One study found that xenarthrans broke off from other placental mammals around 100 Mya.