Mitracarpus maxwelliae is a rare species of flowering plant in the coffee family

Rubiaceae

The Rubiaceae is a family of flowering plants, variously called the coffee family, madder family, or bedstraw family. The group contains many commonly known plants, including the economically important coffee , quinine , and gambier , and the horticulturally valuable madder , west indian jasmine ,...

 known by the common name Maxwell's girdlepod. It is endemic to Puerto Rico

Puerto Rico

Puerto Rico , officially the Commonwealth of Puerto Rico , is an unincorporated territory of the United States, located in the northeastern Caribbean, east of the Dominican Republic and west of both the United States Virgin Islands and the British Virgin Islands.Puerto Rico comprises an...

, where it is known only from the Guánica Commonwealth Forest

Guánica State Forest

The Guánica State Forest is a subtropical dry forest located in southwest Puerto Rico. The area was designated as a forest reserve in 1919 and a United Nations Biosphere Reserve in 1981...

 in Guánica

Guánica, Puerto Rico

Guánica is a municipality in southwestern Puerto Rico located on southern coast, bordering the Caribbean Sea, south of Sabana Grande, east of Lajas, and west of Yauco. It is part of the Yauco Metropolitan Statistical Area....

. It grows in only one location in a coastal scrub forest and dwarf forest with limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

 gravel

Gravel

Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...

 substrates. Other plants in the habitat include Bucida buceras, Bursera simaruba

Bursera simaruba

Bursera simaruba, commonly known as the Gumbo-limbo, is a tree species in the family Burseraceae, native to tropical regions of the Americas from the southeasternmost United States south through Mexico and the Caribbean to Brazil and Venezuela...

, Exostema caribaeum, Coccoloba microstachya, Plumeria alba

Plumeria alba

Plumeria alba is a species of the genus Plumeria . This large evergreen shrub has narrow elongated leaves, large and strongly perfumed white flowers with a yellow center. Native from Central America and the Caribbean, it is now common and naturalized in southern and southeastern Asia....

, and Pilosocereus royenii.

This is a small, dense, mound-forming shrub

Shrub

A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...

 growing up to 20 centimeters in height. It has many four-angled branches with linear or lance-shaped leaves each 1 to 3 centimeters long. The inflorescence

Inflorescence

An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...

 is a rounded head of tiny white flowers.

This is a federally listed endangered species

Endangered species

An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 of the United States. There are fewer than 1500 individuals left. The species is threatened by road construction and maintenance, and its small population size makes it vulnerable to extinction

Extinction

In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

.