The little-known Tetragonia pentandra, long regarded as a member of Aizoaceae in the Horn of Africa region, is included in a phylogenetic analysis using ITS sequence data of members of Betoideae (Chenopodiaceae). Patellifolia, including Tetragonia pentandra, is strongly supported as monophyletic and weakly supported as sister to a clade with Aphanisma, Oreobliton and Beta. Within Patellifolia relationships are largely unresolved and, as the characters that have been used to distinguish taxa in the group are found to be unreliable, we propose that all members of the Patellifolia clade are treated as a single variable species, P. procumbens. Synonymies of Patellifolia and of P. procumbens are provided and two names are lectotypified. The distribution of P. procumbens is mapped and shown to be widely disjunct between the W Mediterranean region/Macaronesia and the Horn of Africa region, with isolated occurrences also in the Saharan mountains.