Selenicereus anthonyanus (Alexander) D.R.Hunt (formerly Cryptocereus anthonyanus) is a perennial climbing succulent, forming branches in clusters. The stems are flat, like an Epiphyllum, but with alternate projections on each side. The stems can grow up to 50 cm or more, and often curved downwards. It is very difficult to get to bloom, but if one is lucky the results are spectacular, the night blooming flowers have white, pink and red petals and are very beautiful. The buds are big 10 cm long and the flowers are huge 15 or more cm wide and sweetly scented. S. anthonyanus is an isolated species with no close allies, Selenicereus chrysocardium seems to be the closest relative. Two other epiphytic cacti from other genera show similar strongly notched flat stems and which, when not in flower, are not readily distinguishable from this species: these are Epiphyllum anguliger and Weberocereus imitans, but S. anthonyanus has flowers with a stouter, much shorter tube and bristly pericarpel. 
In Addition to a slimmer leaf-like appearance, the photosynthesising stem of this plant produces small adventitious roots along its surface that allow it to grip on to trees and climb as high as possible to obtain maximum light, but is adaptable to terrestrial habits. It is relatively common where found, though not very abundant and the threats are not severe enough to warrant a threatened listing. The main threat is deforestation for cattle ranching. 
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A bit about the genus confusion:  he type specimen was collected on February 9, 1951 in a tropical rainforest in the Selva Negra region of Chiapas by the Scottish botanist and explorer of southern Mexico, Thomas MacDougall. MacDougall got the plant to Edward Johnston Alexander, curator at the New York Botanic Garden and this plant first bloomed there on January 2, 1954. Alexander described the plant as a species of Epiphyllum with the specific epithet chrysocardium, meaning "gold heart" for the attractive golden stamen filaments set inside the middle of the white flower. He published this description in the January-February 1956 issue of Journal of the Cactus and Succulent Society of America , though the first actual mention of what was then tentatively called "Epiphyllum of Blanca Rosa" was in the November-December 1953 issue of this same journal in an article by Thomas MacDougall titled "In the Wetlands of Northern Chiapas". In 2003 Myron Kimnach, the Director of the Huntington Botanic Garden from 1962 until 1986, reassigned this plant to the genus Selenicereus. The name Chiapasophyllum chrysocardium has been proposed for this plant as well but some botanical name databases, such as Kew's Plants of the World Online, continue to list this plant under its original name Epiphyllum chrysocardium.
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Genus name is derived from Σελήνη (Selene), the Greek moon goddess, referring to the nocturnal flowers, and cereus, meaning "candle" in Latin, a name used for upright cacti.