What is "rhytidocaulon"

Rhytidocaulon is a plant genus in the family Apocynaceae, first described in 1962. It is native to northeastern Africa and the Arabian Peninsula

Species

1. Rhytidocaulon paradoxum P.R.O.Bally - Ethiopia
2. Rhytidocaulon piliferum Lavranos - Somalia
3. Rhytidocaulon richardianum Lavranos - Somalia
4. Rhytidocaulon subscandens P.R.O.Bally - Somalia, Ethiopia
5. Rhytidocaulon tortum (N.E.Br.) M.G.Gilbert - Arabia

species with undetermined affinities Taxonomy

Phylogenetic studies have shown the genus to be monophyletic, and most closely related to the Echidnopsis genus which inhabits the same region. Marginally more distantly related is a sister branch comprising the Pseudolithos genus and the widespread Caralluma stapeliads of North Africa.