Study On Leguminosae (Dalbergia, Acacia And Sophora) In The Late Miocene Of Lincang,Yunnan Province, China

Yunnan, located in the southwestern border of China, accommodates the most diverse plant species within the transition zone of Holarctic region and Paleotropical area, where different plant populations are gathering and communicating. In Yunnan, dry and wet seasons are obvious and the difference of temperature between winter and summer is small. Lincang City is located in the southwest of Yunnan Province, which is an important area for studying the plant of Cenozoic in our country. Lincang has a lot of intermountain basins. These basins contain a series of well developed outcrops and present abundant plant fossils. These fossil plants are preserved as leaves, fruits, seeds and wood. The study of these fossil plants not only facilitates us better understanding of the composition and characteristics of paleoflora, but also provides the evidence of global paleoflora evolution and the development of plant diversity in the Cenozoic.Leguminosae fossil plants from late Miocene sediment (Bangmai Formation) of Lincang, Yunnan Province are studied in this paper. By the means of comparative morphology between fossil and extant species, eight species of three genera are indentified. The genus Dalbergia includes Dalbergia cf. mecsekense, Dalbergia sp.1, and Dalbergia sp.2. Both fossil records and molecular systematics suggest that this genus may originate from African continent in late Paleocene, and then it migrate through two possible routes to become diversification. Acacia species are Acacia cf. farnesiana, Acacia cf. sinuate, Acacia sp.l and Acacia sp.2. On the basis of fossil records, the similarity of different floras worldwide, the distribution pattern of extant species and its favorable transoceanic ability of Acacia, it is suggested that Acacia may migrate through two possible routes after it originated from the area between Mexico and Bolivia in the Eocene or earlier. Additionally, Sophora paraflavescens is recognized and described.