''Haptanthus'' is a

monotypic genus In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

containing the sole species ''Haptanthus hazlettii'', a shrub or small tree known only from the locality of Matarras in the Arizona Municipality in

Honduras Honduras, officially the Republic of Honduras, is a country in Central America. It is bordered to the west by Guatemala, to the southwest by El Salvador, to the southeast by Nicaragua, to the south by the Pacific Ocean at the Gulf of Fonseca, ...

. Its flowers are unique among the

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

s. A single "female" (carpellate) flower has two branches on either side which carry "male" (staminate) flowers. The flowers are very simple, lacking obvious

sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 Etymology The term ''sepalum'' ...

s or

petal Petals are modified leaves that form an inner whorl surrounding the reproductive parts of flowers. They are often brightly coloured or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corol ...

s. The

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

placement of the genus has been uncertain but based on molecular phylogenetic research, it is included in the family

Buxaceae The Buxaceae are a small family of six genera and about 123 known species of flowering plants. They are shrubs and small trees, with a cosmopolitan distribution. A seventh genus, sometimes accepted in the past (''Notobuxus''), has been shown by ...

. Very few individuals have ever been found, and its habitat is threatened by logging.

Description

''Haptanthus hazlettii'' is a shrub or tree. It has opposite leaves spaced at apart, usually arranged in two ranks (distichous). The leaves are simple with untoothed (entire) margins. There are no

stipule In botany, a stipule is an outgrowth typically borne on both sides (sometimes on just one side) of the base of a leafstalk (the petiole (botany), petiole). They are primarily found among dicots and rare among monocots. Stipules are considered part ...

s. The leaf stalk (

petiole Petiole may refer to: *Petiole (botany), the stalk of a leaf, attaching the blade to the stem *Petiole (insect anatomy) In entomology, petiole is the technical term for the narrow waist of some hymenopteran insects, especially ants, bees, and ...

) is short, long, the leaf blade (lamina) long by wide. The entire plant is hairless (glabrous). The flowers are unisexual, carried on the same

inflorescence In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...

(i.e. the plant is

monoecious Monoecy (; adj. monoecious ) is a sexual system in seed plants where separate male and female cones or flowers are present on the same plant. It is a monomorphic sexual system comparable with gynomonoecy, andromonoecy and trimonoecy, and contras ...

). One (or occasionally two) inflorescences emerge from a leaf axil, with at least five inflorescence-bearing axils per fertile branch. The inflorescences have a unique structure among flowering plants. In the centre there is a single carpellate ("female") flower. This lacks obvious

s or

s (although there are small bracts below the flower which some researchers have suggested may be the remnants of the perianth), and consists solely of a single-celled ( unilocular)

ovary The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/ oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are end ...

, long by wide, surmounted by three curved long stigmas. On either side of the solitary carpellate flower there are two branches each with five or six staminate ("male") flowers arranged at intervals. The structure of the staminate flowers has been interpreted differently. The original describers of the species, Aaron Goldberg and Cirilo Nelson, considered that each staminate flower was basically just a single

stamen The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

, with a flattened filament about long grading into an anther about long. Two staminate flowers from the original specimen were re-examined by Andrew Doust and Peter Stevens. They concluded that each staminate flower definitely had two anthers, closely pressed together. They were unable to make a firm choice between two interpretations. The first is that the staminate flowers are basically as described by Goldberg and Nelson, except there are two stamens with fused or closely pressed filaments and anthers rather than one. The second, which they preferred, is that Goldberg and Nelson's "filament" is actually a pedicel (i.e. a stem on which the parts of the flower are carried) and that their "anther" consists of two closely pressed structures each made up of a

tepal A tepal is one of the outer parts of a flower (collectively the perianth). The term is used when these parts cannot easily be classified as either sepals or petals. This may be because the parts of the perianth are undifferentiated (i.e. of very ...

with a fused anther inside it. Either way, the flowers of ''Haptanthus hazlettii'' have "a morphology unlike that of any other angiosperm".

Taxonomy

The sole species was first discovered in 1980 when a single specimen was collected by Donald L. Hazlett. It was described scientifically in 1989 by Goldberg and Nelson, as a new genus and species, ''Haptanthus hazlettii''. Initially Goldberg and Nelson were unable to assign ''Haptanthus'' to a

. Nelson later placed it in its own family, Haptanthaceae. In 2005, an attempt was made to obtain DNA for sequencing from the only known specimen, but this failed. Based on an analysis of the morphology of the specimen, Doust and Stevens suggested that ''Haptanthus'' was possibly related to the Buxales. The

APG III system The APG III system of flowering plant classification is the third version of a modern, mostly molecular-based, system of plant taxonomy being developed by the Angiosperm Phylogeny Group (APG). Published in 2009, it was superseded in 2016 by a f ...

of 2009 accepted the family Haptanthaceae, placing it in the order Buxales, along with the Buxaceae. The close relationship with the Buxaceae was confirmed in 2011 when DNA was successfully obtained from a newly collected specimen. Molecular phylogenetic analysis showed that ''Haptanthus'' belongs inside the family Buxaceae rather than in a family of its own. The

APG IV system The APG IV system of flowering plant classification is the fourth version of a modern, mostly molecular-based, system of plant taxonomy for flowering plants (angiosperms) being developed by the Angiosperm Phylogeny Group (APG). It was publish ...

of 2016 includes ''Haptanthus'' in the family Buxaceae.

Distribution, habitat and conservation

''Haptanthus hazlettii'' has only been found in a very small area of tropical rain forest on the northern coast of

, close to Matarras in the Arizona Municipality. After the original specimen was collected in 1989, numerous attempts were made to find the species again but without success; the area had become covered with grass following tree clearance. It was thought that the species was perhaps extinct. In 2010 an expedition organized b
Alexey B. Shipunov
and Ekaterina Shipunova found a single tree from the original collection point. A few more were later found nearby. Work to conserve the species is being led by the Lancetilla Botanical Garden of

Tela Tela is a town, with a population of 39,920 (2023 calculation), and a municipality in Honduras on the northern Caribbean coast. It is located in the Atlántida department, department of Atlantida. History Colonial era Tela was founded by th ...

, Honduras.

References

External links

* – includes photographs of the original 1980 specimen {{Taxonbar, from1=Q15715555, from2=Q133951 Buxaceae Eudicot genera Monotypic eudicot genera Flora of Honduras Critically endangered plants