Castillon, J.-P. & J.-B. Castillon (2018). A new threatened species of Euphorbia sect. Goniostema (Euphorbiaceae) from northern Madagascar. Candollea 73: 187–191. In French, English and French abstracts. DOI: http://dx.doi.org/10.15553/c2018v732a2

Euphorbia longitubicinicyathium J.-P. Castillon & J.-B. Castillon (Euphorbiaceae), a new species from northeastern Madagascar is described and illustrated with field photographs. The new species belongs to Euphorbia sect. Goniostema Baill. ex Boiss. and is morphologically related to non thorny species of the east coast of Madagascar (e.g. Euphorbia geroldii Rauh, Euphorbia robivelonae Rauh or Euphorbia thuarsiana Baill.) but differs by its larger dimensions, its habit and its long trumpet shaped cyathia.