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Abundant fossil records indicate that the genus Smilax L was widely distributed in North America and Europe during the Paleogene and thrived in the Miocene. However, since the early Pliocene, the fossil occurrence of Smilax has become very rare. In this study, we describe three leaf taxa of Smilax from the upper Pliocene of West Yunnan, Southwest China based on their leaf architecture and cuticle features. Smilax tengchongensis sp. nov. and Smilax cf. bracteata Presl differ from each other both in leaf shape and cuticle features. The leaves of Smilax sp. possess a different shape and venation but share similar cuticle features with those of S. tengchongensis sp. nov. The morphological diversity of our fossils indicates that a warm and humid climate with a multilayered structure existed in the Pliocene forests of West Yunnan. Moreover, recent molecular studies indicate that both New World and Old World species of Smilax exhibited an intercontinental disjunct distribution via the Beringia land bridge between East Asia and North America. However, this biogeographic disjunction is not well demonstrated by the fossil records as a result of inadequate paleobotanical data. (C) 2017 Elsevier B.V. All rights reserved.

Phylogenetic analyses indicate that the genus Podocarpus diverged around the Cretaceous/Paleogene boundary, and two monophyletic subgenera Podocarpus and Foliolatus had differentiated during the Paleogene. Most of described fossil remains were related to the subgenus Podocarpus, but those of the subgenus Foliolatus have not been well documented. Here, we described a new species of Podocarpus, P. yunnanensis sp. nov., and P. cf. forrestii from the lower Pliocene of western Yunnan, China based on a detailed comparisons of gross leaf morphology and cuticular structures between the studied fossils and extant Podocarpus. These two fossil taxa together with P. pliomacrophyllus H. Chen et J.Y. Wu from the same horizon, revealed a thriving of Podocarpus in western Yunnan during the Pliocene. For the subgenus Foliolatus, its early representatives might originate from Australasia and spread northward to northeastern India at least during the late Oligocene. The Neriifolius subclade within the subgenus is much older than the estimate of molecular clock studies, and the Indochinese subclade is probably derived from a rapid diversification driven by the continuous uplift of Hengduan Mountains (HDM) with the accompanying climate fluctuations since the late Miocene. Moreover, the thriving of Podocarpus in the Pliocene of western Yunnan reveals a warm and humid climate during that period. The Pleistocene glaciation and the geographic barriers posted by the HDM might contribute to the modern distribution of Podocarpus in South China and Indochina Peninsula.

The fossil record of Quercus subgenus Cyclobalanopsis can be traced back to the Late Eocene of eastern Asia based on fossil foliage and acorns. We refer new occurrences of leaf and acorn fossils from the upper Miocene of Tiantai, eastern Zhejiang, China, to two new species, Quercus paraglauca sp. nov. and Quercus heterobracteolata sp. nov.. Q. heterobracteolata represents the earliest confirmed fossil acorn of the subgenus Cyclobalanopsis in China. A review of other occurrences reported in the literature reveals that the divergence of subgenus Cyclobalanopsis occurred not later than the Eocene, and in the Miocene Cyclobalanopsis was already widely distributed. Comparisons of cuticular structure between Q. paraglauca and its nearest living relative species (NLR) Q. glauca suggest that: 1) atmospheric CO2 concentration in the late Miocene was ca. 400 ppmv, i.e. higher than the present natural CO2 concentration, eliminating the industrial influence; 2) the Q. glauca trichome base density is sensitive to the environmental changes; and 3) the late Miocene climate of Zhejiang (eastern China) was warmer and more humid than today.

Two fossil leaves identified as Castanopsis presclerophylla n. sp. collected from a diatomite bed in the upper Pliocene (3.3–2.8 Ma) in Tengchong County, Yunnan Province, Southwest China, are characterized by elliptic laminar shapes with acuminate apex, convex base, simple trichome bases and cyclocytic stomata. The cuticles of extant leaves from six selected Castanopsis species that are similar to the Pliocene fossil leaves in laminar shape were examined in detail for the comparison. Based on the analysis of leaf architecture and cuticular characteristics, the present fossil leaves most closely resemble the extant leaves of Castanopsis sclerophylla (Lindl.) Schott., which prefers a subtropical climate. The published fossil records of Castanopsis also indicate that it was once widely distributed in North America, Europe and Asia before the Pliocene, and then rapidly retreated to the East and Southeast Asia as a result of the Pleistocene glaciation.

Well preserved late Pliocene-early Pleistocene megafossil leaves of Betula yunnanensis Zhi-Cheng Lin et Bai-Nian Sun sp. nov. were collected from the Mangbang Formation in southeastern Tengchong County, West Yunnan Province, China. Species determination was achieved by comparing the leaf architecture, cuticle and fine venation of the newly discovered specimens with thirty-four extant Betula species occurring in China and Japan, and four selected extinct species from China and Poland. Leaf architecture shows that the fossil species are most similar to the species of section Betulaster. Cuticular analysis of all the six species found in China and Japan belonging to section Betulaster (including Betula alnoides, B. rhombibracteata, B. cylindrostachya, B. luminifera, B. maximowicziana, B. fujianensis) was subsequently performed. Comparisons made between the extant and the extinct species confirm that based on leaf size, numbers of lateral vein and trichome types, B. yunnanensis is a new species. An explanation of why and how the peltate scales are only preserved as shield remains in the fossil materials is given. (C) 2010 Elsevier B.V. All rights reserved.

Specimens of Palaeocarya (Juglandaceae) were collected from the upper Pliocene of western Yunnan Province, which is a new geographical and age range record of engelhardioid winged fruits in China. A numerical taxonomic investigation based on 14 morphological characters of fossil and extant specimens of engelhardioid winged fruits in China was conducted using multivariate methods. Phenetic clustering shows that there are four morphotypical groups which we assign to four species. Two groups are assigned to the previously described fossil species, Palaeocarya guangxiensis Li Hao-Min et Chen Yun-Fa, 2003 and Palaeocarya koreanica (Oishi) Manchester, 1987. Two new species are recognized, Palaeocarya yunnanensis and Palaeocarya longialata. These Neogene Engelhardieae fruits provide fossil data for understanding the origin and evolution of the Engelhardia species that now inhabit South China.

Although both fossil pollen and molecular data support a long evolutionary history for the Aquifoliaceae, reliable macrofossils have rarely been described. Here, a new species, Ilex protocornuta Xiang-Chuan Li et Bai-Nian Sun sp. nov. from the Late Miocene Xiananshan Formation of Zhejiang Province, East China, which is unequivocally identified based on eighteen leaf macrofossils, can be placed in the subgenus Ilex section Ilex subsection. The new species shows the closest affinity to Ilex cornuta Lindley et Paxton. A survey of Ilex fossil records (pollen and leaves) from the Cretaceous to the Pliocene in China suggests that the past distribution of fossil Ilex species is much wider than that of extant species, while the occurrence of the probably evergreen I. protocornuta may indicate that a warm and humid climate similar to that of today existed in East China during the Late Miocene, which is also supported by the co-occurring plants that prefer a tropical, subtropical or warm-temperate habitat (i.e. Smilax, Lagerstroemia and evergreen Quercus). (C) 2010 Elsevier B.V. All rights reserved.

Eight fossil leaves identified as Exbucklandia tengchongensis sp. nov. (Hamamelidaceae) were collected from the Pliocene Mangbang Formation in Tengchong, Yunnan Province, Southwest China. The fossil leaves are characterized by the overall rounded lamina with entire margin, actinodromous venation, and cyclocytic stomata, which suggest the affinity within the genus Exbucklandia , particularly with E. populnea . A survey on the cuticles of the sun and shade leaves of modern E. populnea indicates that the shade leaves generally possess more pronounced undulate anticlinal cell walls and a much lower stomatal density than the sun leaves. Two morphotypes, i.e. sun vs. shade types, of the fossil leaves were therefore recognized. The distribution of the modern Exbucklandia suggests that the genus lives under a warm climate with a mean annual temperature (MAT) from 13 °C to 27 °C and a mean annual precipitation (MAP) from 800 mm to 2500 mm. Hence, E. tengchongensis might also live under a similar climatic condition in the Pliocene. Leaf margin analysis on the Tengchong flora supports this result. The little change of Neogene MAT in Southwest China is therefore supported.

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.