Rebutia (Aylostera) sumayana was originally described in the Dutch journal Succulenta 65(4), pp. 73-5, together with a colour photograph, by Walter Rausch in 1986.

Here is the text of the description of this species in the original Latin, together with some additional notes by Rausch, in Dutch, and my own English translations. You should look up the original description for more details, including the photograph.

Rebutia (Aylostera) sumayana Rausch spec. nov.

W. RAUSCH

Simplex vel paulum proliferans, globosa ad oviformis, ad 20 mm diametiens, laete-viridis, radicibus
carnosis; costis ca. 1 6, paulum tortis, in tubercula verrucosa, 2-3 mm longa divisis; areolis rotundis vel paulum ovalibus, 1 mm longis, albo- ad fusco-tomentosis; aculeis marginalibus 9-11-13, accumbentibus ad divaricatis, inter se contextis, setosis, albis (vel fuscis), 2-3 mm longis; aculeo centrali 0-1, id est uno superiore sursum directo, ad 4 mm longo, albo (vel fusco ad nigro). Floribus 30 mm longis et 25 mm diametientibus, ovario et receptaculo ochraceoalbido, squamis ochraceis, lana et setis albis tecto; phyllis perigonii exterioribus et interioribus aurantiacis; fauce 10-12 mm longa, ventricoso-arcuata, paululum cum stylo connata, albidorosea, filamentis albis, basi roseis, stylo ad 18 mm longo, tenui, viridulo, stigmatibus 6, tenuibus, viridulo-albis. Fructu globoso, spadiceo, lana et setis albis tecto. Seminibus globosoelongatis, 1 mm longis, pallide-nigris, hilo magno recto.

Patria: Bolivia, Cinti australis, prope Sumaya, 3200 m alt.

Typus: Rausch 738, depositus in Collectione Plantarum Succulentarum Municipali Turicensi, Flelvetia.

Additional notes

De planten van deze soort zijn zo variabel, dat er geen twee hetzelfde zijn. De afstand tussen de areolen kan zeer gering tot relatief groot zijn. De bedoorning kan zowel kort als lang zijn, waarbij de kleur nog varieert van wit tot bruin of zwart. De bloembladen kunnen rond tot spits uitlopen.
In 1963 beschreef Ritter Rebutia tuberosa, een species die uit dezelfde omgeving komt. Daar hij van deze species geen variatiebreedte opgeeft, was ik in het begin in de veronderstelling dat species R 738 tot deze soort behoorde. Er kon evenwel vastgesteld worden dat R. tuberosa, ook in de nakomelingen, bij alle planten een duidelijk langere bedoorning als ook een meer gestrekt lichaam tentoonspreidt.
Derhalve heb ik besloten, deze lichter groene, meer bolvormig groeiende planten uit de omgeving van Sumaya als een aparte soort te beschrijven.

English translation

Body singular or proliferating and then forming groups, spherical to oval, up to 20 mm in diameter, light green; root system fleshy. Ribs approx. 16, slightly twisted, divided into tubercles of 2-3 mm. Areoles round or slightly oval, 1 mm long, with white (to brown) wool. Marginal spines 9-11-13, adjacent to spreading, intertwined, bristly, white (also brown), 2-3 mm long; central spine 0-1 or, more correctly, an upper spine standing forward, up to 4 mm long, white (or brown to black). Flower 30 mm long and 25 mm wide; ovary and flower tube very light ochre, with ochre scales, white wool and long bristles; outer and inner petals orange-red; throat 10-12 mm long, belly-curved, only slightly fused with the pistil, whitish pink; anthers white with pink base; pistil up to 18 mm long, thin, greenish; stigma with 6 thin, greenish-white lobes. Fruit spherical, reddish brown, with white wool and bristles. Seed slightly elongated spherical, 1 mm long, matte black, with large, straight navel.

Habitat: Bolivia, south of Cinti in the vicinity of Sumaya at an altitude of 3200 m.

Holotype Rausch 738, deposited in the Stadtische Sukkulentensammlung from Zurich.

The plants of this species are so variable that no two are alike.

The distance between the areoles can be very small to relatively large. The spines can be either short or long, with the colour varying from white to brown or black. The petals can be rounded to pointed.

In 1963, Ritter described Rebutia tuberosa, a species native to the same environment. Since he does not specify a range of variation for these species, I initially assumed that species R 738 belonged to this group. However, it could be established that in R. tuberosa, and also in the progeny, displays significantly longer spines as well as a more elongated body in all plants.

I have therefore decided to describe these lighter green, more bulbous rooting plants from the vicinity of Sumaya as a separate species.