It sounds like you mean a sloth. There are a few varieties and they generally do hang upside down on the underside of tree limbs.
sloth
opossum
Ocelot
Monkeys and sloths can hang upside down in trees and they usually have grey or brown fur. Meerkats can also hang upside down in trees and have grey or brown fur.
Sloths do
en.wikipedia.org/wiki/Cyclamen
Many people forget about the sloth, a slow creature which spends nearly all its life in trees relaxing. It sleeps, and rests upside down, hanging from the branches by its feet.
i think its FELGE.
Gorillas
There is a risk of asphyxiation of a person hangs upside down for too long. The blood can leave the vessels causing oxygen to not circulate properly. There is not a risk if a person is healthy hanging upside down for short periods of time.
A boar's head, isn't it?
Are you thinking about opossums?