The sori start 'green' and flat then mature to a puffy brown or black usually, from what I can see they look like a horse shoe shape ..
http://hardyfernlibrary.com/fe...
I can also see some fine hairs on the edges.
There are links on the top left once you go to Thelypteris, one is a key on Flora of North America.
http://www.efloras.org/florata...
