The head of the three-toed sloth swivels 270 degrees thanks to three extra cervical vertebrae.
"Because the three-toed sloth has three extra cervical vertebrae than other mammals, including its close relative the two-toed sloth, it is able to turn its head 270 degrees, or three-quarters the way around." (Young 1999)
Learn more about this functional adaptation.
Young, Amy. 1999. Bradypus variegatus. University of Michigan Museum of Zoology.
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