Late Pliocene Bauhinia s.l. (Cercidoideae, Fabaceae) fossils from Tengchong, Yunnan, southwestern China

Bauhinia s.l. widely distributed across tropical and subtropical regions and has a complex taxonomic history and divided into two main clades: the Bauhinia clade and the Phanera clade. The fossil records of Bauhinia s.l. are predominantly found in Asia, but they were reported worldwide. In this study, we describe two leaf fossil taxa of Bauhinia s.l. and one legume fossil taxon from western Yunnan, China. The results of the morphological and phylogenetic analysis indicate that the newly identified species Bauhinia tengchongensis sp. nov. is a part of the Phanera clade. The phylogenetic analysis suggests that the divergence between the two clades likely occurred before the late Oligocene. The fossil distribution and phylogenetic data suggest that South China may have been an early diversity centers for Bauhinia s.l. Given the distribution of extant Bauhinia s.l. members and the warmer climate during the Late Pliocene in Tengchong, we propose that the cooling period following the Pliocene in western Yunnan may have driven the migration of some thermophilic Bauhinia s.l. species towards Eastern and Southern China.