Inversodicraea koukoutamba and I. tassing (Podostemaceae), new waterfall species from Guinea, West Africa

Two new species of Inversodicraea, I. koukoutamba and I. tassing, both from the Republic of Guinea, are described as new to science, increasing the number of species 15 known in this African genus to 32, making it the most species-diverse among African Podostemaceae. Both species are remarkable, among other features, for their styles. Inversodicraea koukoutamba is only the third species of the genus with 3, not 2 styles, and is unique in the genus, and in the family, in having each style bifurcate. Inversodicraea tassing has styles equal or exceeding the length of the ovary, being nearly twice as long as 20 those of the species which previously was noted for the longest styles in the genus. Both new species are single-site endemics, the first is assessed here as Critically Endangered according to the IUCN 2012 standard, due to the incipient construction of the World Bank backed Koukoutamba hydroelectric dam which threatens several other plant species assessed as Critically Endangered or Endangered. The second species, I. tassing, is 25 assessed as Near Threatened, since there are currently no threats known at present to the single known site.