Dilleniaceae) is described from HonBa Nature Reserve of the Khanh Hoa province of Vietnam. Detailed illustrations and taxonomic comments are provided along with a table listing the differential characters to the closely similar taxa. Phylogenetic analyses using nrITS region of ribosomal DNA and psbA-trnH intergenic spacer region of chloroplast DNA sequences were also performed and they supported the status of D. tetrapetala as a distinct species. The plant is considered endangered based on the IUCN red list criteria because of its restricted distribution.

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