[Qem]

> Giant sloths was not really on my list of expected answers

Despite not looking very alike at the first glance, sloths are grouped together with armadillos in the clade Xenarthra[1]. Both lineages descend from a common ancestor from around the time the dinosaurs went extinct. So it's not that surprising there were burrowing sloths. I guess the burrowing behaviour surely came handy to their shared ancestor by the time the dinosaurs were screwed by the asteroid that carved the Chicxulub crater[2]. What is mind-boggling for me is that once there were aquatic sloths[3]. Some sloths followed the steps from the ancestors of whales and dolphins, and rehearsed a return to sea. Unfortunately that evolutionary experiment was cut short when the gap between south and north america closed, isolating atlantic from pacific oceans and dooming the niche where the critters thrived. Had they persisted, I wonder if by now we could have whale-like sloths (whaloths?).

[1] https://en.wikipedia.org/wiki/Xenarthra

[2] https://en.wikipedia.org/wiki/Chicxulub_crater

[3] https://en.wikipedia.org/wiki/Thalassocnus

[beambot]

Manatees and dugongs feel like "whale-like sloths", though I have no idea if they're taxonomically related

[Qem]

They are more closely related to elephants.

[bloopernova]

Thank you for the aquatic sloth link, that's so cool!