The Neogene flora from Badaogou of Changbai, NE China — Most similar living relatives of selected taxa and relations to the European record

The diatomites exposed in the surroundings of Badaogou town, in the counties of Linjiang and Changbai, Jilin Province of China, bear a rich Neogene leaf assemblage. Previously, the most similar living relatives (MSLRs) of Sassafras paratsumu Chen (Lauraceae), Acer rotundatum Huzioka (Sapindaceae, subfam. Aceroideae, sect. Platanoidea), and A. trifoliatum Geng (Sapindaceae, subfam. Aceroideae, sect. Trifoliata) have been determined based solely on gross morphology. Cuticle preservation in the plant material from Badaogou allows the comparison of epidermal features. Thus, Sassafras tzumu (Hemsley) Hemsley is confirmed as the unambiguous MSLR of S. paratsumu.The cuticular features of Acer rotundatum best match A. mono Maximowicz and A. cappadocicum Gleditsch. Only the stoma and aperture length are slightly shorter in A. mono than in A. cappadocicum, therefore more closely resembling A. rotundatum.Based on gross morphology, earlier workers already regarded A. triflorum Komarov as the MSLR of Acer trifoliatum. The cuticle, however, bears some differences. In A. trifoliatum the stomata are slightly bigger, the adaxial surface is only faintly, if at all, striate, and the anticlinal walls are straight; in A. triflorum, however, the anticlinal walls are undulate and the surface shows distinct striation. Compared to other East Asian members of sect. Trifoliata – A. griseum (Franchet) Pax, A. mandshuricum Maximowicz, and A. maximowiczianum Miquel – the combination of features match best with A. triflorum. This includes leaflet shape and size, trichome bases of simple, filiform trichomes girdled by roundish cells, and the presence of uniserial, short-celled, glandular trichomes in intercostal areas abaxially.The modern counterparts of the fossil taxa are elements of the modern flora of China.