The Raccoon Family: Kinkajous - the primate-like "raccoons"

Raccoons proper are well-known animals, both familiar and distinctive even to those of us living in countries where they are not native. Among the other members of the raccoon family, coatis are at least familiar to people in the southern US. Ringtails ("cacomistles") are probably more obscure, being smaller and mostly active high up in trees at night, but at least, they too, live in the US. The remaining species, however, live only in Latin America and it's probably fair to say that they are much less familiar to English speakers than those groups with more northerly representatives.

Perhaps the most distinctive, and certainly the most studied, of these is a genus with just one species: the kinkajou (Potos flavus). It was first scientifically described by Johann Schreber in 1774, in an earlier volume of the book in which he would later describe (among other things) cheetahs, snow leopards, and bobcats. While he was understandably clear those were all cats, the identity of the kinkajou was not so obvious. In the days before Darwin, this may not have held any deep meaning for him, but his conclusion was that his new animal was a kind of lemur.

How Sloths Turned Upside Down

One of the things that sloths are noted for is spending a lot of time hanging upside down. This isn't, of course, something they literally spend their entire lives doing; they come down out of the trees to defecate, and they do sometimes travel over the ground - or swim across rivers - to move from one tree to another. They have also been observed, especially in zoos, casually sitting about in what we'd consider a fairly normal posture. But even so, being upside down is how they spend most of their time.

This is obviously pretty odd, from the perspective of a mammal (or, indeed, most other animals). You might think that what must have happened is that, at some point in the distant past, some ancestral tree sloth first headed up into the branches, decided to do so by hanging from them rather than by the more obvious method favoured by (say) primates, and that all of its descendants simply happened to do the same thing. In other words, it's a one-off quirk of evolution.

Except that can't be right.