What feature gives the pygmy marmoset the nickname 'lion monkey'?

Answer

Longer hairs around the face and neck forming a mane

The presence of longer hairs around the face and neck creates a feature that resembles a lion’s mane, which is one of their most distinguishing physical attributes.

What feature gives the pygmy marmoset the nickname 'lion monkey'?
animalmammalappearancePrimatePygmy Marmoset