Sorry, that is a very juvenile sporeling baby of some Thelypteris species. It's no use collecting or photographing sporelings like that one.. Collect from the adult plants in the vicinity.
It is such a baby that I don't think the vein anastomoses developed properly yet, and as you did not photograph it with light behind it, we can't see the venation anyway. The most likely is a baby T. (Christella) dentata. But at this stage it is unidentifiable.
Yours,
Chris F.-J., Birmingham.