Ranunculusmaoxianensis (Ranunculaceae), a new species from northwestern Sichuan, China, with an emended description of R.chongzhouensis , the putative closest ally of the new species.

Ranunculusmaoxianensis (Ranunculaceae), a new species from Jiuding Shan in Maoxian county, northwestern Sichuan province, China, is here illustrated and described. The species is morphologically similar to R.chongzhouensis , a species also occurring in Sichuan, in having reniform leaves and puberulous receptacles, carpels and achenes, but differs by having leaves adaxially puberulous with shorter appressed hairs 0.16‒0.28 mm long (vs. longer appressed hairs 0.55‒0.85 mm long), larger flowers (1.8‒2 cm vs. 1.4‒1.6 cm in diameter), larger (8‒10 × 5.5‒6.5 mm vs. 6‒7 × 4.5‒5 mm) and widely obovate petals (vs. obovate), more numerous stamens (35‒55 vs. 12‒18), and subglobose gynoecium and aggregate fruit (vs. ellipsoid). The two species are also different in chromosome number and chromosome morphology. Ranunculuschongzhouensis has a karyotype of 2 n = 2 x = 16 = 10m + 6sm while R.maoxianensis has a karyotype of 2 n = 4 x = 32 = 16m + 16sm. An emended description of R.chongzhouensis is provided, and its geographical distribution is largely extended.