Question: While Gymnocalycium is of the cactus genus, what genus is the Rhynchostylis?

Context articles: Gymnocalycium baldianum
Gymnocalycium fischeri
Gymnocalycium nova
Gottfried Knebel
Gymnocalycium oenanthemum
Gymnocalycium mihanovichii
Moonlight cactus
Rhynchostylis
Gymnocalycium eurypleurum
Gymnocalycium

Gymnocalycium baldianium is a species of cacti of the genus Gymnocalycium.
Gymnocalycium fischeri is a globular cactus belonging to the family Cactaceae.
 The first description was in 2002 by Josef Halda Jacob, Petr Kupčák, Emil Lukasik and Jaromír Sladkovský.
 The specific epithet honors the Czech cactus collector Ladislav Fischer.
Gymnocalycium nova is a globular cactus.
 Plants have a round appearance and spines that are curved back towards the body.
 The cactus grows in South America, enjoys full sunlight, and is very drought resistant.
 The species includes the cultivar 'Sierra Medina'.
Gottfried Knebel (born 1908) was a German botanist.
 He was the author of the cactus genus "Opuntiopsis", an invalid name according to the current rules of botanical nomenclature; it is now a synonym of "Schlumbergera".
 The species "Mammillaria knebeliana" is said to have been named in his honour.
Gymnocalycium oenanthemum is a species of cactus.
 It is endemic to Argentina.
Gymnocalycium mihanovichii, often called chin cactus, is a species of cactus from South America commonly grown as a houseplant.
 The most popular cultivars are varied mutants which completely lack chlorophyll, exposing the red, orange or yellow pigmentation.
 These cultivars are often called "moon cactus".
 Since chlorophyll is necessary for photosynthesis, these mutations die as seedlings unless grafted onto another cactus with normal chlorophyll.
Moonlight cacti, genus Selenicereus, is an epiphytic, lithophytic, and terrestrial cactus genus found in Central America, the Caribbean and northern South America.
Rhynchostylis (abbreviated Rhy in the horticultural trade) is a genus in the orchid family (Orchidaceae), closely allied to the genus "Vanda" (from which it differs in the one-lobed lip of the flower) and comprising four currently accepted species native to the Indian Subcontinent, China, Indochina, Malaysia, Indonesia and the Philippines.
 The name consists of a compound of two Greek elements : "rhynchos" 'beak' and "stylis" 'column' - in reference to the very boad, fleshy column of the flower.
Gymnocalycium eurypleurum is a small "chin cactus" that is highly prized by cactus collectors and is known to be fairly easy to grow, albeit very slow It has been cultivated outside in latitudes as far north as Modesto, California.
 In the wild, the species is almost always solitary (non-clumping) and may grow in association with "Frailea" species.
 The species when grown in the greenhouse is also known for its fidelity to wild specimens.
 It is said to live in seasonally very dry habitat (annual rainfall 50 - ), clay soils between 6.8–7.2 pH, and maximum temperatures to 50 C .
Gymnocalycium, commonly called chin cactus, is a genus of about 70 South American species of cactus.
 The genus name "Gymnocalycium" (from Greek, "naked calyx") refers to the flower buds bearing no hair or spines.