Miocene Exbucklandia (Hamamelidaceae) from Yunnan, China and its biogeographic and palaeoecologic implications

Exbucklandia acutifolia J. Huang et Z. K. Zhou sp. nov. fossil foliage and Exbucklandia sp. (Hamamelidaceae) fossil stipule are reported from early-middle Miocene lacustrine sediments in Wenshan, Yunnan, southwest China. The nearest living relative of the new fossil-species is E. tonkinensis, a species which is restricted to the Sino-Japanese Region. The fossil record also shows that this genus was widespread in East Asia and North America: species with slender leaves and acute leaf base originated early in this genus. The extinction of Exbucklandia in North America resulted in this genus being endemic to East Asia. Local scale biogeography indicates that our fossil record shows the distribution area of Exbucklandia to be different in the Miocene than today: the Sino-Himalayan species expanded while the distribution of the Sino-Japanese species receded. Moreover, morphological traits of E. acutifolia suggest that precipitation levels in the Wenshan region were higher than those of the current levels.