''Sigmoidala'' is a

monotypic 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 "unispec ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. They include all forbs (flowering plants without a woody stem), grasses and grass-like plants, a vast majority of ...

s in the family Fabaceae, first established in 2019. Its only species is ''Sigmoidala kityana'', native to

Myanmar Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John Wells explai ...

, northern

Thailand Thailand ( ), historically known as Siam () and officially the Kingdom of Thailand, is a country in Southeast Asia, located at the centre of the Indochinese Peninsula, spanning , with a population of almost 70 million. The country is b ...

and Laos. It was first described by William Grant Craib in 1927 as ''Millettia kityana''.

Description

''Sigmoidala kityana'' is a robust woody twining

vine A vine ( Latin ''vīnea'' "grapevine", "vineyard", from ''vīnum'' "wine") is any plant with a growth habit of trailing or scandent (that is, climbing) stems, lianas or runners. The word ''vine'' can also refer to such stems or runners thems ...

. Its young stems are very dark green. Its leaves are evergreen and generally have 6–8 pairs of leaflets plus a terminal leaflet. The

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. Morphologically, it is the modified part of the shoot of seed plants where flowers are formed ...

is a robust terminal

panicle A panicle is a much-branched inflorescence. (softcover ). Some authors distinguish it from a compound spike inflorescence, by requiring that the flowers (and fruit In botany, a fruit is the seed-bearing structure in flowering plants that is ...

long, with many flowers. Individual flowers are long and have the general shape of members of the subfamily

Faboideae The Faboideae are a subfamily of the flowering plant family Fabaceae or Leguminosae. An acceptable alternative name for the subfamily is Papilionoideae, or Papilionaceae when this group of plants is treated as a family. This subfamily is widely ...

. The standard

petal Petals are modified leaves that surround the reproductive parts of flowers. They are often brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corolla''. Petals are usuall ...

is long by 12–13 mm (0.5 in) wide. Its inner surface is white flushed pink with a broad golden-yellow nectar guide. The wing petals are longer than the keel at long by wide, but are curved towards the end and so appear shorter. They have short basal claws. The keel petals are long by 4–6 mm (0.2 in) wide. Nine of the

stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filam ...

s are fused together, the other is free; all curve upwards at the apex. The flattened seed pods are long by wide, splitting to release the seeds, of which there are generally 1–5, occasionally up to 8.

Taxonomy

The species was first described as ''Millettia kityana'' by William Grant Craib in 1927.

Anne M. Schot Anne M. Schot (born 1966) is a Netherlanders#Terminology in Dutch and other languages, Dutch botanist. Early life Anne M Schot was born on 20 September 1966 in Leidschendam, a town in South Holland province, Netherlands (Leidschendam has ...

transferred it to ''

Callerya ''Callerya'' is a genus of flowering plants in the legume family, Fabaceae. It belongs to the subfamily Faboideae. Genetic analysis shows ''Callerya'' and ''Wisteria'' to be each other's closest relatives and quite distinct from other members of ...

'' in 1995. A 2019

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

study showed that it fell outside the clade containing the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

of ''Callerya'', and established the new genus ''Sigmoidala'' for this species. The generic name refers to the sigmoid-shaped wing petals. Its closest relatives are ''

Endosamara ''Endosamara'' is a monotypic genus of flowering plants in the legume family Fabaceae, tribe Wisterieae. Its only species is ''Endosamara racemosa'', a liana found from South India through Indo-China to the Philippines. Description ''Endosam ...

'' and ''

Sarcodum ''Sarcodum'' is a genus of flowering plants in the legume family, Fabaceae. It belongs to the subfamily Faboideae, tribe Wisterieae. Its three species are twining vines growing over shrubs, and are native from southeast mainland China to the Sol ...

'', from which it can be distinguished in a number of ways. The wing petals of ''Sigmoidala'' are unique within the tribe Wisterieae in having a sigmoid shape, bent sharply back at the midpoint before extending forwards again. The flattened seed pods of ''Sigmoidala'' are shorter than those of ''Endosamara'' and also differ from the sausage-shaped pods of ''Sarcodum''.

Distribution and habitat

Plants of the World Online Plants of the World Online (POWO) is an online database published by the Royal Botanic Gardens, Kew. It was launched in March 2017 with the ultimate aim being "to enable users to access information on all the world's known seed-bearing plants ...

listed the distribution of ''Sigmoidala kityana'' as

to north and north-eastern

and Laos, growing primarily in the seasonally dry tropical

biome A biome () is a biogeographical unit consisting of a biological community that has formed in response to the physical environment in which they are found and a shared regional climate. Biomes may span more than one continent. Biome is a broader ...

. Compton et al. (2019) state that it only occurs in a narrow region of northern and north-eastern Thailand, where it climbs among dry forest trees in partial sunlight at elevations up to .

References

{{taxonbar, from1=Q94060749, from2=Q94303829, from3=Q15485004, from4=Q15484674 Wisterieae Monotypic Fabaceae genera