Puerto Rico Maiden Fern

Goniopteris yaucoensis, synonym Thelypteris yaucoensis, is a rare species of fern known by the common name Puerto Rico maiden fern. It is endemic to Puerto Rico, where it is known from only three localities. It is a federally listed endangered species of the United States.

This fern was placed on the endangered species list in 1993. At that time it was known to exist at three locations: two in Yauco and one in Ciales in Puerto Rico. There were a total of about 65 plants known at all three combined.