"Summary: Rhipsalis flagelliformis, sp. no., is described from Rio de Janeiro state, where it is narrowly endemic. It superficially resembles the Mexican Disocactus flagelliformis and cannot be confused with any other Rhipsalis species. In habit the plant appears to be highly neotenic, retaining the seedling characters typical of some members of its genus. According to gene sequence data it belongs in Rhipsalis subg. Goniorhipsalis and shares some features with the related R. lindbergiana, R. pacheco-leonis and R. pentaptera, but differs from these in its conspicuously spiny stems. Its IUCN Red List conservation status is determined as Critically Endangered."
The article contains superb photos of the plants in habitat but we cannot reproduce them here because of copyright.