Aylostera (Rebutia (Digitorebutia)) christinae was first described by Walter Rausch in Kakteen und andere Sukkulenten 26(7): 145, 1975, the journal of the Deutsche Kakteen-Gesellschaft.

Here is the text of the description of this species in the original Latin, but you should look up the original description for more details, including further details in German and photographs. The English translation below is my own.

Rebutia (Digitorebutia) christinae RAUSCH spec. nov.
Walter Rausch
Simplex, globosa, ad 25 mm diametiens, clare-viridis, radice napiformi; costis 12—13, perpendicularibus vel subtortis, 6—7 mm latis et planioribus, crenis parvis transversis in gibberes 3 mm longos divisis; areolis ovalibus, 2 mm longis, albo- ad fusco-tomentosis; aculeis marginalibus 7-8 paribus, ad 7 mm longis, inter se contextis, vitreo-albis ad flavidis, basi incrassata brunneis; aculeo centrali 1, ad 5 mm longo, validiore, flavido, basi incrassata fusco et fuscoacuminato.
Floribus 30 mm longis et 30 mm diametientibus; ovario globoso, rubro-fusco, receptaculo roseo, squamis fuscis ad viridibus, pilis et setis albis tecto; phyllis perigonii exterioribus subspathulatis, roseis medio-albido-viridi-striatis; phyllis perigonii interioribus spathulaterotundis, aurantiacis; fauce 15 mm longa, 4 mm eius cum stylo connata, albida; filamentis roseis, sursum aurantiacis stylo 15 mm longo, viridi , stigmatibus 8, flavis.
Fructu globoso, 5 mm diametiente, fuscoviolaceo, pilis et setis albis tecto. Seminibus subelongatis, 1 mm longis et 0,8 mm diametientibus, campanulatis vel subcurvatis, nigris, tunica arillosa reliqua glauca tectis, hilo magno basali.
Patria: Argentina, Salta inter Nazareno et Rodeo, 3.500 m alt.
Typus: Rausch 492a in Herbario Musei Historiae Naturalis Vindobonensi (Herbario W.)

English translation

Rebutia (Digitorebutia) christinae RAUSCH spec. nov.
Walter Rausch

Single, spherical up to 25 mm diameter, light green, with a tap root, ribs 12-13, vertical or slightly twisted, 6-7 mm wide and fairly flat, divided into 3 mm long cusps by small transverse notches, areoles oval, 2 mm long, white to brown tomentose, radial spines arranged in 7-8 pairs, up to 7 mm long, intertwined, glassy white to yellowish with a thickened, brown base, central spine 1, up to 5 mm long, somewhat stronger, yellowish with a thickened, brown base and brown tip.

Flower 30 mm long and 30 mm diameter, ovary spherical, red-brown and tube pink with brown to green scales, white hair and bristles, outer petals somewhat spatulate, pink with whitish-green central stripes, inner petals spatulate-round, orange, throat 15 mm long and 4 mm of it fused with the style, whitish, stamens pink with upper part orange, style 15 mm long, green, stigmas 8, yellow.

Fruit spherical, 5 mm diameter, brown-violet with white hairs and bristles, seeds somewhat elongated, 1 mm long and 0.8 mm diameter, bell-shaped or slightly curved, covered in black with green-grey remains of skin, and a large, basal umbilicus.

Habitat: Argentina, Salta, between Nazareno and Rodeo, at an altitude of 3500 m.
Type: Rausch 492a in the Herbarium of Natural History Museum of the City of Vienna.