“Little did Ai know, his portrait would inspire thousands of awkward high school portraits, more than 250 years later.”

Image: Maned three-toed sloth - Bradypus torquatus.
From Verzameling van uitlandsche en zeldzamme vogelen, benevens eenige vreemde dieren en plantgewassen. George Edwards and M. Catesby, 1781.

“Ai siue Ignavus” - Bradypus tridactylus

The title “Ai siue Ignavus” translates to “Ai, or Lazy”, which were the two common names for the Pale-throated sloth at the time. The Bradypus genus is the genus of three-toed sloths, which are the ones who are descended from a common ancestor of the giant ground sloths - two-toed sloths are actually not closely-related to either three-toed or giant sloths. 

Even though they’re not closely-related, both sloth families share a unique trait: they don’t have seven cervical vertebrae, which is a trait of almost all mammals, including those with very short necks (such as whales) and very long necks (such as giraffes). The two-toed sloths have only six cervical vertebrae, and the three-toed sloths have nine cervical vertebrae. The extra vertebrae in the three-toed sloths are what allow them to have such flexibility in their neck, and how they can turn their head 180 degrees.

A Description of the Nature of Four-Footed Beasts. Joannes Jonstonus, 1678.