The subfamily Centothecoideae s.s, distributed worldwide in the tropical and subtemperate regions, comprises 10 genera (Bromuniola, Calderonella, Centotheca, Chasmanthium, Chevalierella, Lophatherum, Megastachya, Orthoclada, Pohlidium and Zeugites). It was defined originally by embryo formula (P+PP and F+PP), tessellation of the leaf-blades, pseudopetiolate leaves, small herbaceous habit, and forest habitat, as well as by the differentiation of the mesophyll into palisade and spongy tissue, but its cohesiveness was questionable and its relationships were uncertain. In the last two decades, certain other genera (Cyperochloa, Danthoniopsis, Gouldochloa, Gynerium, Spartochloa, and Thysanolaena) have been segregated from other subfamilies and placed in or suggested as members of the centothecoid clade; a sister relationship between the centothecoids in the broad sense (including these genera) and the Panicoideae also has been inferred. These findings were based mainly on molecular data and some morphological data also, although at present there is no morphological synapomorphy that supports the centothecoids as monophyletic. Consequently, the position of these genera with respect to the centothecoids, and the circumscription of the centothecoid clade itself, remain uncertain. We present a preliminary morphological and anatomical comparison of the Centothecoideae s.s. and the putatively related genera, as well as a preliminary phylogenetic analysis using molecular and morphological data. According to the morphoanatomical data, leaf anatomy in cross section, the venation of the leaf blades, and the arrangement of the unisexual florets in the spikelets are likely to be the most informative features.

Key words: Centothecoideae, informative characters, monophyly, sister group