Based on a plastid, morphological and nuclear phylogeny, Chemisquy et al. (pp. 107–130) show that the genera Pennisetum, Cenchrus and Odontelytrum form a monophyletic group with high support. The nuclear phylogenetic analysis reveals a reticulate pattern of relationships among Pennisetum and Cenchrus. Consequently, the species of Pennisetum and Odontelytrum are transferred to Cenchrus, which has priority.
M. A. Chemisquy, L. M. Giussani, M. A. Scataglini, E. A. Kellogg, O. Morrone, 2010, 'Phylogenetic studies favour the unification of Pennisetum, Cenchrus and Odontelytrum (Poaceae): a combined nuclear, plastid and morphological analysis, and nomenclatural combinations in Cenchrus', Annals of Botany, vol. 106, no. 1, pp. 107-130 http://dx.doi.org/10.1093/aob/mcq090