The Middle Miocene Alum Bluff flora in northwestern Florida provides a valuable opportunity for comprehending former floristic diversity and the development of modern temperate forest in southeastern North America. The flora previously was understood to be dominated by deciduous subtropical to temperate taxa. Here, we present newly discovered winged fruits of the tropical genus Illigera (Hernandiaceae). The new fossil species, Illigera berryi Hai Zhu, Manch. et T.A. Lott is the first confirmed thermophilic macrofossil record from the flora and enriches the known floristic diversity. This occurrence expands the paleogeographic distribution of Illigera in North America southeastward and extends the known fossil history of the genus from the Eocene to the Middle Miocene. Combined with previously recognized fossil occurrences from the Eocene of western North America and eastern Asia, the fossil evidence indicates that Illigera had a wide distribution in the Cenozoic, and suggests that the genus may have originated from the Northern Hemisphere.

The Hengduan Mountains region (HMR) on the southeastern Tibetan Plateau, supports a high diversity of herbs, particularly in its subalpine to alpine ecosystems, due to high altitude and cool temperate climate. Current understanding on the formation of such herbaceous richness is based chiefly on molecular phylogenies; however, direct geological evidence is lacking because herbs are rarely preserved as macroscopic fossils. In this study, we present abundant fossil fruits and seeds of herbs from the late Pliocene Heqing Basin in the southern HMR. Our systematic analysis shows the presence of at least 18 species belonging to 11 genera, that is, Ranunculus, Corydalis, Rumex, Polygonum, Chenopodium, Stellaria, Fragaria, Astragalus, Aster, Carex, and Schoenoplectus, of which Polygonum is most abundant followed by Astragalus. This finding throws the first light from fossil evidence on the rise of herbaceous diversity in the region. We interpret the local assembly of these herbs as resulting from rapid pre-Pliocene species diversifications of many herbaceous groups in the HMR. As nowadays most of these herbs grow primarily in meadows and a few occur as subaquatic plants, we suggest an open meadow hosting some scattered shrubs in the vicinity of a vegetated wetland in the Heqing Basin during the late Pliocene. This provides the first direct evidence of past treeless open vegetation within the HMR and thus improves our knowledge of vegetation evolution in the region. We suggest that the uplift-induced climate cooling and monsoon-associated precipitation seasonality are potentially the key driving forces for the opening of meadow vegetation in the HMR.

Sambucus L. (Adoxaceae) has a rich fossil record with a major concentration in Europe and North Asia but a scarcity in relatively low latitudes of the Northern Hemisphere. Herein, we report fossil endocarps of the genus from the late Pliocene Heqing Basin of northwestern Yunnan, South China, which are assigned to two species, namely S. alveolatisemina and S. heqingensis Huang et Zhou sp. nov. Sambucus alveolatisemina has been formerly described from the similar geological horizon of the nearby Lanping Basin in northwestern Yunnan and possibly represents the fossil equivalent of S. adnata, an extant species commonly seen in this and neighboring regions. Sambucus heqingensis is newly erected due to its exceptionally slender endocarp shape together with the irregularly ridged endocarp surface and straight lateral margins. Our fossil discovery, in combination with the two fossil taxa from the late Pliocene Lanping Basin, suggests that the diversity of Sambucus might have risen in South China by the late Pliocene. We conclude that, as compared to Europe and North Asia, the distribution and diversification of the genus in South China with much lower latitudes is likely to be a recent event. This can be properly explained by the fact that Sambucus is generally a temperate element while the climate in South China in prior to the Pliocene might be too warm for its inhabitation. We propose a hypothesis that the colonization and diversification of the genus in other low-latitude regions of the Northern Hemisphere might have been similarly late in time.

Aims: Due to complex geomorphology and diverse landscapes, the southern Hengduan Mountains region is home to highly diverse vegetation.The evolution and formation of such diversity is an interesting topic in the fields of botany and ecology, and plant fossils are an important proxy for researching this question.Method: In this study, we integrated published sources of nine fossil floras from the Pliocene of the southern Hengduan Mountains region.We first inferred the vegetation types of these fossil floras on the basis of their taxonomic compositions and dominant elements, and then depicted the diversity and spatial distribution of vegetation in the regionduring the Pliocene.We also correlated the rise of vegetation diversity and the formation of vegetation distribution to major environmental changes in the southern Hengduan Mountains region.Results: Our synthesis indicates that the southern Hengduan Mountain region already held a variety of vegetation types during the Pliocene, including subtropical evergreen broadleaved forest, subtropical deciduous broadleaved forest, sclerophyllous evergreen broadleaved forest, mixed coniferous broadleaved forest and shrubby meadow.The vegetation tended to have a warm affinity in the south and a cool-temperate affinity in the north, demonstrating altitudinal gradients with latitude at that time.Moreover, vegetation types are shown to be stratified at some localities, suggesting altitudinal gradients at local scales that are likely associated with the occurrence of high mountains.These are highly similar to the modern patterns of vegetation diversity and distribution in this region. Conclusion:Our study concludes that the modern diversity and distribution of vegetation in the southern Hengduan Mountain region was established no later than the Pliocene.However, more plant fossils from deeper times are needed to verify if the current vegetation was formed at an earlier geological age.

Premise of research. Our concept of the former diversity and geographic spread of Platanaceae continues to expand. Unlobed platanaceous leaves have been poorly known in the fossil record of western North America. New information on the extinct Paleogene genus Platimeliphyllum and its associated reproductive structures is helping to unravel the biogeographic and evolutionary history of Platanaceae.Methodology. We studied leaves of Platimeliphyllum and associated platanaceous inflorescences and infructescences from the Eocene of western North America and northeastern China. Epidermal anatomy was obtained from cuticle fragments macerated in Schultze solution and studied using transmitted light and epifluorescence microscopy. In situ pollen from inflorescences was studied using light microscopy and SEM.Pivotal results. We provide new evidence supporting the platanaceous affinity of Platimeliphyllum and document its occurrence in the Eocene of western North America as well as in eastern Asia. We present the new combinations Platimeliphyllum durhamensis (Wolfe) comb. nov. from Washington and Oregon and Platimeliphyllum fushunensis (Chen) comb. nov. from Fushun, Liaoning Province, northeastern China. This extends the geographic range of a genus previously known mainly from the Paleocene and Eocene of Russia and Kazakhstan. The ovate, unlobed, simple laminae correspond to Platanaceae in their marginal teeth with rounded sinuses, straight secondary veins, agrophic veins, and orthogonal tertiary and quaternary venation. The association of these leaves with platanaceous inflorescences further confirms their affinities with Platanaceae.Conclusions. Platimeliphyllum likely spread between North America and Asia via the Bering Land Bridge in the Paleocene or Eocene. Previous climate estimates of the Fushun flora based on the coexistence approach need reevaluation with the updated taxonomy of the flora. The co-occurrence of Platimeliphyllum with Macginitiea, Platanites, and Platanus indicates that an array of platanaceous lineages coexisted during the Eocene in western North America.

Yunnan at southeastern margin of the Tibetan Plateau is subject to frequent wildfires each year, while its wildfire history remains poorly known due to the lack of studies on palaeofire in the region. In this study, we report a local fire from the late Pliocene of northwestern Yunnan, based on macroscopic fossil charcoals recovered from the Sanying Formation of Lanping Basin. These sedimentary charcoals exhibit silky lustre in the light and complete homogenization of adjacent xylem cell walls, characterizing the result of incomplete combustion during the late Pliocene. Our preliminary taxonomic analysis indicates that the studied charcoals are dominated by conifers, suggesting higher importance of coniferous elements as fuel sources in the fire. We assert a conifer-rich source forest for the fire event by also considering plant remains of other types, i.e., needle fragments, small shoots, fruits and seeds, from the same sampling layer. Since conifers are commonly prone to wildfires, this type of forest might have a close link with the fire by serving highly flammable fuels. We consider that the regionally seasonal drought during the late Pliocene might also take responsibility, because in the dry season forest fuels such as ground litter would become ignitable after intensive desiccation. As modern wildfires in northwestern Yunnan are closely coupled with conifer-dominant forests and seasonally dry climate, we assume this correlation might have been established by the late Pliocene. Our study may bring attention to potential roles of wildfire on local and/or regional flora and vegetation evolution in this region.

Premise of research. Acer leaf and samara fossils are abundant and readily recognized in the Cenozoic of western North America. Inferences as to which of the fossil leaves and samaras are conspecific require data on site co-occurrence and on the morphological similarities of these organs to extant species for which the linkage of leaves and samaras is known. Accurate assignment of these fossils will be helpful for our understanding of the biodiversity and biogeographic history of the genus through geologic time. Here we reinvestigated Miocene fossils attributed to section Rubra Pax. s.l., including leaves of A. chaneyi Knowlton and the associated fruits of A. gigas Knowlton, in comparison with extant and other fossil representatives of this section. Methodology. Fossil and extant samaras were studied by reflected light supplemented by micro-computed tomography scanning to reveal some endocarp and seed characters difficult to document by traditional methods. Fossil leaves were studied by reflected light, and cleared leaf slides of extant species were studied on the light table. Pivotal results. Fruits and leaves of the extant species, A. rubrum L., A. saccharinum L., A. pycnanthum K. Koch, and A. laurinum Hassk., show characters supporting the previously recommended merger of sections Rubra Pax. s.s. and Hyptiocarpa Fang. Acer gigas samaras, commonly considered to represent the same plant as A. chaneyi, show some morphological differences from extant A. saccharinum, although the A. chaneyi leaves greatly resemble those of that extant species. These and other fossils from western North America, Europe, and Asia indicate a previously wide distribution of section Rubra. Conclusions. New characters of fruit morphology support the subsuming of section Hyptiocarpa within Rubra s.l. We retain the name A. gigas for samara fossils, associated with the leaf fossils of A. chaneyi, and provide emended descriptions for them.

Coniferous forests represent one of the most important vegetation types in the southern Hengduan Mountains on southeastern edge of the Tibetan Plateau, but their evolutionary history remains poorly understood. Here, we report an upper Pliocene charcoal assemblage from the Sanying Formation at Fudong in the Lanping Basin, which represents remains of a mixed coniferous forest. Taxonomic studies indicate that the charcoal assemblage is dominated by Pinus armandii with a subordinate component of Cupressoideae, a few other conifers (Abies, Picea, Tsuga) and some angiosperms (Quercus, Rhododendron, Rubus, Sambucus, Zanthoxylum, Aralia, Amaranthaceae, Polygonum, Carex). Based on the present-day climate association of P. armandii, we consider that the reconstructed mixed coniferous forest to be of warm-temperate affinity. Some altitudinal variation of plant communities likely existed, with cool-temperate elements (Abies, Picea) occurring in higher altitudes on the mountain slope, warm-temperate elements (P. armandii, Tsuga, Quercus, Rubus, Rhododendron, Sambucus) in mid-altitudes, and warm elements (Zanthoxylum, Aralia) in lower altitudes. Due to the occurrences of Abies and Picea, we infer the presence of mountains >3000 m altitude near Fudong, which further constrains the timing of significant uplift prior to the late Pliocene. Together with fossil pollen data, our findings indicate that the southern Hengduan Mountains was increasingly dominated by conifers during the late Pliocene, particularly in its subalpine to alpine ecoregions, probably due to the progressive onset of cool and dry climates caused by regional uplift. Synthesising vegetation types, we conclude that the region showed large-scale vegetation zonation during this epoch, which generally ranged from evergreen broadleaved forests of warm affinity in the south to mixed coniferous forests of more temperate affinity in the north. The vegetation zonation can be interpreted as being shaped by large south-to-north altitudinal gradients due to uneven rates of uplift.

Staphylea has abundant isolated seeds in the fossil record, but no fossil fruits of this genus have been confirmed before. In this paper, we report a capsular fruit of Staphylea from the Oligocene Renova Formation of Woodworth, western-central Montana, USA. Detailed investigation of this fruit gives new insights on the phylogenetic and biogeographic history of the genus. Morphological comparison with modern Staphylea fruits shows its closest resemblance to the extant Asian species, S. bumalda DC., which is similar in fruit shape, size, and pericarp venation, but differs by the angle of interlobal sinus and the stipe development. We establish a new fossil species, S. woodworthensis Zhu & Manchester sp. nov. for this fossil fruit. This discovery indicates that Staphylea was already established in western North America at least by the Oligocene, which is inconsistent with the recent interpretation of a late Oligocene origin of the genus in Europe. The distribution of fossils indicates an earlier diversification of Staphylea, along with other staphyleaceous genera, back to early Paleogene in North America. The genus subsequently retracted its range to the east and south in North America as evidenced by younger fossils and its modern geographic range.

The subfamily Rosoideae Focke (Rosaceae) has a good fossil record in the Northern Hemisphere, but these fossil records are confined mainly to a few genera, whereas the majority, in particular those with herbaceous members, are still under-represented. In this study, we describe new fruit fossils of Rosoideae, including Fragaria achenes and Rubus endocarps, from the late Pliocene of northwestern Yunnan, Southwest China. These fossils add new accounts to the fossil archive of Rosoideae and provide the first fossil record of Fragaria in East Asia. The new fossil findings provide a historical backdrop for the modern diversity and distribution of the subfamily in northwestern Yunnan, a topographically complex area accommodating a high diversity for many plant groups. Our Rubus fossils, in combination with other nearby coeval occurrences of the genus, suggest that Rubus was already establishing its modern diversity in northwestern Yunnan during the late Pliocene. This finding enriches our knowledge of the post-Neogene diversification of flowering plants in northwestern Yunnan, which is thought to be largely driven by dramatic mountain uplifts and environmental complications associated with the southeastern extension of the Tibetan Plateau.

Fossil seeds of Zanthoxylum L. (Rutaceae) were studied from three fossil floras in Yunnan Province, Southwest China, the late Miocene Shuitangba, late Pliocene Fudong, and early Pleistocene Nanbanbang. Based on seed morphological characters, the Shuitangba seeds were assigned to a new fossil species, Zanthoxylum trachyspermum sp. nov. H. Zhu et Z.K. Zhou, the Fudong seeds were determined only at the generic level, and the Nanbanbang seeds were designated to a modern species, Zanthoxylum avicennae (Lam.) DC. These three new fossil records, together with Z. tertiarium (Heer) Gregor et Hantke from the early to middle Miocene Mangdan flora and modern distributions of Zanthoxylum in Southwest China, imply that Zanthoxylum has continuously existed in this region at least since the early to middle Miocene. Quaternary glaciations have not caused the disappearance of Zanthoxylum from Southwest China, differing from the situation in Europe where the genus was well represented prior to the Pleistocene but became extinct thereafter. The severe post-Miocene environmental changes caused by the continuous uplift of the Qinghai-Tibet Plateau and adjacent areas might have promoted the establishment of its modern high diversity in Southwest China through enlarging environmental heterogeneity.

Eurya has an excellent fossil record in Europe, but it has only a few fossil occurrences in East Asia though this vast area houses the highest modern diversity of the genus. In this study, three-dimensionally preserved fossil seeds of Eurya stigmosa (Ludwig) Mai from the late Pliocene of northwestern Yunnan, southwestern China are described. The seeds are compressed and flattened, slightly campylotropous, and nearly circular to slightly angular in shape. The surface of the seeds is sculptured by a distinctive foveolate pattern, consisting of funnel-shaped and finely pitted cells. Each seed valve contains a reniform or horseshoe-shaped embryo cavity, a characteristic condyle structure and an internal raphe. These fossil seeds represent one of the few fossil records of Eurya in East Asia. This new finding therefore largely extends the distributional ranges of Eurya during Neogene. Fossil records summarized here show that Eurya persisted in Europe until the early Pleistocene, but disappeared thereafter. The genus might have first appeared in East Asia no later than the late Oligocene, and dispersed widely in regions such as Japan, Nepal, and southwestern China.

Fossil fruits of Palaeocarya (Juglandaceae) are described from late Miocene sediments of southeastern Yunnan, China. The fruits present a tri-lobed wing consisting of an intact oblong-ovate middle lobe and two lateral lobes. The lobes are apically obovate, and have pinnate venation. The middle lobe is thicker at the base and gradually tapers to the apex. The nutlet, located at the base of the winged fruit, is round and hispid, and is subdivided by a septum into two compartments. Based on extensive morphological comparisons to previously documented fossil fruits, we found that the fossil fruits align most closely with members of the genus Palaeocarya, but have a unique combination of characters. Thus, we describe the fossils as a new species, Palaeocarya hispida sp. nov. This species represents an important range expansion for low-latitude occurrences of Palaeocarya in the late Miocene and therefore substantially improves our understanding of the biogeographic history of the genus. We propose that the wide distribution of Palaeocarya and relatively narrow distributions of close relatives, Engelhardia, Alfaropsis, and Oreomunnea, might be associated with a stepwise cooling and a major ice sheet expansion in the Antarctic and Arctic from the late middle Miocene to early Pliocene. In particular, the climatic oscillations during the Quaternary, such as the last glacial maximum, might have led to a decrease in the geographic distribution of Engelhardieae.

Aralia stratosa H. Zhu, Y.J. Huang et Z.K. Zhou sp. nov. is described based on fossil endocarps from the upper Pliocene of northwest Yunnan in southwest China. The endocarps are characterized by a semicircular to elliptic outline in the lateral view, an apical beak-like structure bending towards the ventral side, and a transversely wrinkled surface, collectively indicating taxonomical inclusion in the genus Aralia (Araliaceae). The new fossil taxon is compared with nine extant species of Aralia based on endocarp morphology and anatomy, showing the carpological resemblance to A. echinocaulis. Aralia stratosa sp. nov. represents the first confirmed fossil record from lower latitudes in the Northern Hemisphere. This implies a southerly biogeographical range for this genus than was previously interpreted. The fossil record of Aralia suggests a Cretaceous origin in North America and an Eocene dispersal to eastern Asia, likely via the Bering land bridge, followed by Miocene establishment in Europe. The genus likely began to inhabit lower latitudes in eastern Asia no later than the late Pliocene, which is in line with results from molecular analyses. All these may suggest a southward distributional change probably associated with the global cooling and northern aridification.

选取我国西南地区槭属(槭树科)的8个现生种,通过观察和测量馆藏标本的翅果形态,对比同一个种的翅果在不同地区的形态差异性,并通过主成分分析(PCO)检测翅果在种内的形态变异性,发现槭属的翅果形态具有明显的地区间差异性,这种差异性主要表现在总体形状和大小上,这可能与地区间不同的气候环境特征有关.通过对槭属翅果种内形态变异性和多样性的深入研究,为槭属翅果化石的属下鉴定提供一定依据,指出槭属翅果化石的属下鉴定应该考虑翅果形态种内变异性的特征,具有形态多样性的该属翅果化石可能属于一个种或更少的种.