Monanthotaxis bali (Annonaceae) a new Critically Endangered (possibly extinct) montane forest treelet from Bali Ngemba, Cameroon

Monanthotaxis bali is the only known, solely montane (occurring solely above 2000 m alt.) species of the genus. It joins Monanthotaxis orophila (Rwanda) and M. discolor (Tanzania), two other species that can also occur above 2000 m alt. Monanthotaxis bali is an addition to the small number (28) of the tree species of the surviving montane forests of the Cameroon Highlands of which only eight other species are endemic. Due to its supra-axillary inflorescences, and petals arranged in one whorl but with the outer petals overlapping the inner petals distally, and rounded flower buds, the new species is placed in Hoekstras clade B of Monanthotaxis. The new species is unusual in being a treelet in a predominantly lianescent genus, and in lacking the glaucous underside of the leaf-blades that usually characterises the genus. Monanthotaxis bali takes the number of continental African species of the genus to 80, and makes Cameroon, with 30 species, the most species-diverse country for the genus. Monanthotaxis bali is known only from the Bali Ngemba Forest Reserve, a forest remnant under pressure of degradation and clearance in the Bamenda Highlands of Cameroon. It may already be extinct due to logging and agricultural activities. Here it is described, illustrated, mapped and assessed as Critically Endangered (Possibly Extinct) using the IUCN 2012 criteria.