''Calymmanthium'' 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 "unisp ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of primitive tree-like

cacti A cactus (: cacti, cactuses, or less commonly, cactus) is a member of the plant family Cactaceae (), a family of the order Caryophyllales comprising about 127 genera with some 1,750 known species. The word ''cactus'' derives, through Latin, ...

from northern

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

. The only species is ''Calymmanthium substerile'' (also known as ''C. fertile''). It belongs to the

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...

Lymanbensonieae. The young flowers of ''Calymmanthium'' are completely encased within the plant's

pedicel Pedicle or pedicel may refer to: Human anatomy *Pedicle of vertebral arch, the segment between the transverse process and the vertebral body, and is often used as a radiographic marker and entry point in vertebroplasty and kyphoplasty procedures ...

until it is fully developed, at which time the growing yellow flower swells until it cracks the pedicel open, allowing pollinators access. The plant has an upright trunk, but many of the branches sprawl on the ground.Mauseth, Odyssey, loc.cit. ''Diploperianthium''

F.Ritter Friedrich Ritter (9 May 1898 – 9 April 1989) was a German botanist who collected and described many species of cacti. '' Ritterocereus'' is named in his honour. Friedrich Ritter studied biology, geology and paleontology at the University of Ma ...

(nom. inval.) has been brought into

synonymy A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

with this genus.

References

Cactoideae Cactoideae genera Cacti of South America Endemic flora of Peru Monotypic Cactaceae genera {{Cactus-stub