Page "Xenarthra" Paragraph 1

Xenarthrans share several distinctions from those of other placental mammals.

The name Xenarthra means " strange joints ", and was chosen because their vertebral joints have extra articulations and are unlike those of any other mammals.

The males have internal testicles, which are placed between the bladder and the rectum.

Also, xenarthrans have the lowest metabolic rates among the therians.