''Tectaria estremerana'' is a rare species of

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...

known by the common name Puerto Rico halberd fern.''Tectaria estremerana''.
USDA Plants Profile. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Puerto Rico Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and Unincorporated ...

. It is a federally listed

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inv ...

of the United States.USFWS
Determination of Endangered Status for Four Endemic Puerto Rican Ferns.
''Federal Register'' June 9, 1993. This fern has fronds up to long, each with a hairy, orange brown stipe. The

rachis In biology, a rachis (from the grc, ῥάχις [], "backbone, spine") is a main axis or "shaft". In zoology and microbiology In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this c ...

is hairy and the leaf is divided into a few elongated leaflets. When this plant was placed on the United States' Endangered Species List it was known from a population of 23 individuals in

Arecibo, Puerto Rico Arecibo (; ) is a city and municipality on the northern coast of Puerto Rico, on the shores of the Atlantic Ocean, located north of Utuado and Ciales; east of Hatillo; and west of Barceloneta and Florida. It is about west of San Juan, the ...

. The ferns are located about away from the

Arecibo Radio Telescope The Arecibo Telescope was a spherical reflector radio telescope built into a natural sinkhole at the Arecibo Observatory located near Arecibo, Puerto Rico. A cable-mount steerable receiver and several radar transmitters for emitting signals wer ...

. Later more individuals were discovered in Río Abajo Commonwealth Forest and in the municipality of

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

.USFWS
5-Year Review for 3 Puerto Rican Ferns.
January 2010.

References

estremerana Ferns of the Americas Endemic flora of Puerto Rico Plants described in 1989 Ferns of the United States Flora without expected TNC conservation status {{Polypodiales-stub