Davis & Phillipson: The single sp in Madagascar has been referred to the Afro-Asian C. spinosa. However it appears to be a distinct endemic.
C.M. Taylor: Catunaregam comprises about 6 species of spiny shrubs and small trees found in dry regions of Africa through southern Asia. These species have a distinctive growth form, with the leaves, spines, and flowers borne on lateral short-shoots (i.e., brachyblasts) along well developed stems. The flowers are bisexual and 5-merous, with the corolla generally rather broad and open and its lobes contorted in bud. The fruits are fleshy berries with numerous flattened seeds embedded in the pulp.
Catunaregam spinosa as it is currently treated includes plants from southeastern Africa through India to China, a very broad circumscription that has not been re-evaluated recently (nor has the genus as a whole been studied). Two subspecies of C. spinosa have been recognized, subsp. spinosa found throughout most of the range of the species and subsp. taylorii (S. Moore) Verdc. of southeastern Africa; subsp. taylorii is separated based on its densely velvety pubescence, vs. "not so densely velvety" in subsp. spinosa. Plants from Madagascar have been identified as C. spinosa subsp. spinosa by Bridson and others in sched., however Bridson & Verdcourt (1988: pp. 499-500) did not include Madagascar in the formal summary of the distribution range of this species.