It did not turned out to be C. somalica as labelled but C. speciosa. The perfectly symmetrical ball of inflorescence about 10 cm across is very impressive. Well, the foetid rotten flesh odor will get your attention within a couple of meters. The smell attracts big carrion flies. It took me many tries to get a decent picture - the corona has bright luminescent quality and contrast poorly with the yellow corolla tube; either the corona is overexposed or the dark maroon corolla lobes are underexposed.
This is one of the big clumping Caralluma found in tropical East Africa (Kenya, Tanzania, Uganda & Horn of Africa (Somalia, Ethiopia, probably also in Djibouti or Eritrea) on dry rocky savanna or semi-desert lowland habitat. C. speciosa and other like C. adenensis, C. somalica, C. acutangula (C. retrospiciens) and C. edithae are similar species that can be "grouped" together. Now, am awaiting another big clumping Caralluma sp. purchased from Bangkok to flower.