Metamorphosis for this butterfly appears to have been interrupted by a parasite, a small wasp perhaps. You can see the hole where the parasite chewed its way out. Oddly, there’s a similar hole on the other side. Maybe it abandoned this other exit since it looks incomplete. Or maybe there were actually multiple parasites.
I know this is the chrysalis of a brush-footed butterfly in the family Nymphalidae because other butterfly families use a a small silken thread around the thorax to help secure it. Here’s an example from an earlier post.
Butterfly chrysalises can be quite intricate and this one has some interesting flourishes.
Reference:
[book:0811736245]