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Platycladus Spach is native to Central China, but its natural occurrences are very difficult to establish. According to molecular phylogenetic data, this genus might have originated since the Oligocene, but no fossil record has been reported. Here, we describe eight foliage branches from the upper Miocene in western Yunnan, Southwest China as a new species, P. yunnanensis sp. nov., which is characterized by foliage branches spread in flattened sprays, and leaves decussate, imbricate, scale-like and dimorphic. The leaves are amphistomatic, and the stomata are elliptical or oblong, haplocheilic, and monocyclic type. Based on a detailed comparison with the extant genera of Cupressaceae sensu lato, our fossils are classified into the genus Platycladus. The occurrence of P. yunnanensis sp. nov. indicates that this genus had a more southernly natural distribution in the late Miocene than at present. Molecular phylogeny and fossil records support a pre-Oligocene common ancestor for the genera Platycladus, Microbiota and Calocedrus. The separation of the three taxa was most likely caused by the arid belt across Central China during the Oligocene. In addition, the cooling down of the global temperature and the strengthening of Asian monsoon since the Miocene will further promote the migration of these genera.

Mahonia Nuttall (Berberidaceae Jussieu) is an East Asian‒North American disjunct evergreen genus. There are many fossil records of Mahonia from the Eocene to Pleistocene in North America and Europe, but only a few reliable fossils have been reported from East Asia. Compressed fossil leaflets, described here as Mahonia mangbangensis sp. nov. and Mahonia cf. oiwakensis, were collected from the Pliocene Mangbang Formation in Tengchong County, Yunnan Province, southwest China. These new fossil specimens show the same leaf architectural characteristics as those belonging to the Group Orientales of Mahonia, and represent the youngest occurrence of the genus in East Asia. This new fossil discovery extends the stratigraphic range of Mahonia in East Asia and provides new insights into the potential differentiation and migration routes of the Group Orientales in China. Mahonia probably differentiated during the Pliocene in western Yunnan, representing part of the diversification history of this genus in East Asia. [ABSTRACT FROM AUTHOR]

The cuticular δ13C values and stomatal parameters (stomatal density and stomatal index: SD and SI) of two Betulaceae species, Betula mioluminifera Hu et Chaney and Carpinus miofangiana Nathorst, from a suite of superposed horizons in West Yunnan, southwestern China, were measured in order to recover Late Pliocene CO2 levels. Correlations are given for δ13C, SD, epidermal cell density (ECD), and SI. δ13C reveals a positive trend with the SD and SI in the two species, and such a positive correlation can also be observed between the δ13C and ECD in C. miofangiana. However, δ13C has a slightly negative correlation with the ECD in B. mioluminifera (R² = 0.06), possibly influenced by their different genotypes. Reflecting the changes through time, the δ13C values of B. mioluminifera and C. miofangiana significantly increase with high determination coefficients (R² = 0.67 and R² = 0.65, respectively), as do SD (R² = 0.66 and R² = 0.51, respectively) and SI (R² = 0.50 and R² = 0.79, respectively). Research on extant B. luminifera and C. fangiana shows that the SD and especially SI, exhibit a prominent negative correlation with CO2 concentration. Pliocene CO2 levels are reconstructed as 381.5-439.4 ppmv and 377.8-472.3 ppmv, respectively, based on comparisons of the two fossil species with their nearest living equivalent (NLE) species. The significant positive trends of the δ13C, SD and SI with ascending position of the fossils in the section indicate that the atmospheric CO2 levels declined in the Late Pliocene (3.30-2.83 Ma). Furthermore, the calculated CO2 levels are higher than in other studies and probably demonstrate that local CO2 enrichment can be caused by frequent volcanic eruptions over a long time scale [ABSTRACT FROM AUTHOR]