Leptocereus grantianus (sebucan) is a sprawling or suberect, nearly spineless cactus, reaching up to 2 meters in height and 3 to 5 centimeters in diameter. Its elongated stems have from three to five prominent ribs with broadly scalloped edges. Ribs of young joints are thin, and the small areoles or spine-bearing areas may bear from one to three minute, nearly black spines which disappear as the joints grow older. The flowers are solitary at terminal areoles, from 3 to 6 centimeters long, and nocturnal. The outer perianth segments are linear, green, and tipped by an areole like those of the tube and ovary. The inner perianth segments are numerous, cream-colored, oblong-obvate, obtuse, and about 8 millimeters long. The fruit is subglobose to ellipsoid and about 4 centimeters in diameter.
Varronia rupicola, synonym Cordia rupicola, commonly known as the Puerto Rico manjack, is a critically endangered species of flowering shrub in the borage family, Boraginaceae, that is native to the islands of Puerto Rico and Anegada.
Auerodendron pauciflorum is a rare species of flowering plant in the family Rhamnaceae. One English language common name is turtlefat. It is endemic to Puerto Rico, where it is known from only one population in Isabela. At the time the plant was federally listed as an endangered species by the United States in 1994, only ten individual plants were known to exist. By 1997, there were 19 known specimens.
Buxus vahlii, or Vahl's boxwood, is a rare species of plant in the boxwood family. It is native to Puerto Rico and St. Croix in the U.S. Virgin Islands, where it is known from no more than four populations total. It has probably never been very common, but its distribution has been reduced by deforestation and other human disturbance of its habitat. At the time it was listed as an endangered species of the United States in 1985, it was thought to be endemic to Puerto Rico. Reports that it existed in Jamaica have not been confirmed. A few individuals have been located in St. Croix, some of which are within Sandy Point National Wildlife Refuge.
Eugenia woodburyana is a species of plant in the family Myrtaceae. It is endemic to Puerto Rico. It is a federally listed endangered species of the United States. It is threatened by habitat loss.
Thelypteris is a genus of ferns in the subfamily Thelypteridoideae, family Thelypteridaceae, order Polypodiales. Two radically different circumscriptions of the genus are in use as of January 2020. In the Pteridophyte Phylogeny Group classification of 2016, the genus is a very small one with about two species. In other approaches, the genus is the only one in the subfamily Thelypteridoideae, and so includes between 875 and 1083 species.
Eleutherodactylus juanariveroi, the Puerto Rican wetland frog or, is an endangered species of coqui, a frog species, endemic to Puerto Rico. It was discovered in 2005 by Neftalí Rios, and was named after Puerto Rican herpetologist Juan A. Rivero, in honor of his contributions to Puerto Rican herpetology. It is only found in the old Naval Base of Sábana Seca in Toa Baja, Puerto Rico. It is characterized by a high-frequency, chip-like sound, a light-brown skin color, and a strip between the eyes. It is the smallest species of coqui.
Parathelypteris noveboracensis, synonym Thelypteris noveboracensis, the New York fern, is a perennial species of fern found throughout the eastern United States and Canada, from Louisiana to Newfoundland, but most concentrated within Appalachia and the Atlantic Northeast. New York ferns often forms spreading colonies within the forests they inhabit.
Adiantum vivesii is a rare species of maidenhair fern known by the common name Puerto Rico maidenhair.
Aristida chaseae is a rare species of grass known by the common name Chase's threeawn. It is endemic to Puerto Rico, where it is known from two locations in the Cabo Rojo National Wildlife Refuge and the Sierra Bermeja. It is a federally listed endangered species of the United States. It cannot compete with introduced species of grasses, such as Brachiaria subquadripara, which are invading its habitat.
Aristida portoricensis is a rare species of grass known by the common name pelos del diablo. It is endemic to Puerto Rico, where it is known from two locations, one in a residential area of Mayagüez and one in the Sierra Bermeja. Two other known sites have been extirpated by development of the habitat. It is a federally listed endangered species of the United States.
Cranichis ricartii is a rare species of orchid known by the common name Puerto Rico helmet orchid. It is native to Puerto Rico, where it is known from three locations in one forest. The plant has also been seen in Guadeloupe. The plant's rarity is the main reason for its listing as an endangered species of the United States.
Elaphoglossum serpens is a rare species of fern that grows only on Cerro de Punta, the highest mountain in Puerto Rico. The fern grows at one location, where there are 22 known specimens. It was federally listed as an endangered species of the United States in 1993.
Mitracarpus maxwelliae is a rare species of flowering plant in the coffee family known by the common name Maxwell's girdlepod. It is endemic to Puerto Rico, where it is known only from the Guánica Commonwealth Forest in Guánica. It grows in only one location in a coastal scrub forest and dwarf forest with limestone gravel substrates. Other plants in the habitat include Bucida buceras, Bursera simaruba, Exostema caribaeum, Coccoloba microstachya, Plumeria alba, and Pilosocereus royenii.
Polystichum calderonense is a rare species of fern known by the common name Monte Guilarte hollyfern. It is endemic to Puerto Rico, where it occurs in the Peñuelas and Guilarte Commonwealth Forests. There are only 57 individual plants remaining. It is a federally listed endangered species of the United States.
Tectaria estremerana is a rare species of fern known by the common name Puerto Rico halberd fern. It is endemic to Puerto Rico. It is a federally listed endangered species of the United States.
Amauropelta inabonensis, synonym Thelypteris inabonensis, is a rare species of fern known by the common name cordillera maiden fern. It is endemic to Puerto Rico, where it is known from only two localities: at the headwaters of Río Inabón and at the Toro Negro State Forest. It is a federally listed endangered species of the United States.
Goniopteris verecunda, synonym Thelypteris verecunda, is a rare species of fern known by the common name Barrio Charcas 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.
Vernonia proctorii is a rare species of flowering plant in the aster family known by the common name Proctor's ironweed. It is endemic to Puerto Rico, where there are two populations. It is threatened by the destruction of its habitat. It is a federally listed endangered species of the United States.
