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.
A Guide to North American Species
by Charley Eiseman and Noah Charney