Description from Flora of China
Butneria Duhamel (1755), not Byttneria Loefling (1758), nom. cons.; Meratia Loiseleur-Deslongchamps.
Shrubs or small trees, erect, deciduous or evergreen. Branchlets dichotomous, quadrangular to subterete; winter buds with imbricate scales but exposed in summer. Leaf blade papery or subleathery, adaxially scabrous or ± smooth. Flowers axillary, fragrant, subsessile to very shortly pedicellate. Tepals numerous, yellow, yellowish white, or white and sometimes with purple markings, membranous, varying in size and shape from outer to inner but not distinctly dimorphic. Stamens 5-8, arranged on cuplike receptacle; filaments filamentous but basally broad and connate, usually puberulent; staminodes few to numerous, puberulous, arranged inside stamens on receptacle. Carpels 5-15, distinct; ovules 2 per carpel but 1 ovule usually abortive. Pseudocarp urceolate, ovoid-ellipsoid, obovoid-ellipsoid, or campanulate, pubescent. Achenes oblong, oblong-ellipsoid, ellipsoid, oblong-ovoid, or reniform.
It is estimated that the Chinese species diverged from each other perhaps as recently as 1-2 million years ago, and the presently available molecular evidence distinguishes all six species but groups Chimonanthus campanulatus and C. praecox separately (with a bootstrap support of 100) from the other four species (S. L. Zhou et al., Molec. Phylogenetic. Evol. 39: 1-15. 2006). However, the molecular evidence is based on a limited number of samples, mostly from botanical gardens. It is difficult to morphologically circumscribe differences to distinguish all six species. Because the molecular evidence does distinguish all six species, it seems best to treat all six in this account but to point out that additional research may well change this interpretation. It is the opinion of one co-author (Bartholomew) that perhaps there are really only two species, C. praecox and C. nitens, with the other named species being attributable to one or the other or introgressions between the two.
● Six species: China.