I'll add details (forgive my ignorance of correct technical terms) since I just grabbed one of those left-over fronds and am looking at it:

The fronds are arranged like a crown (like the native sword fern) rather than single and upright (like a bracken fern).

Each leaflet along the main stem is quite finely cut, and the longest ones are about 3 inches long. The tips of many of these larger leaflets branch or divide about five times, which is what gives the fern its curly "frill".

Once the main stem divides into branches towards its end, fewer of the leaflets have frilly divisions (and they are less finely cut), but many still do frill, especially at the tip of each branch.

Aha. I've answered my own question, I think.

I believe it is a crested male fern, Dryopteris filix-mas Crispa Cristata. (What is the difference between this and Dryopteris uniformis? There is a crested version of that one, too...).

It's a very beautiful fern!

Picture link below.

Here is a link that might be useful: male fern