First flower inclusion and fossil evidence of Cryptocarya (Laurales, Lauraceae) from Miocene amber of Zhangpu (China)

Lauraceae have one of the oldest fossil records of angiosperms with the earliest known evidence from the mid-Cretaceous. However, most of these records are based on leaves, especially from the Cenozoic of Asia, which are often challenging to assign to extinct or extant genera or species. In contrast, fossils of reproductive organs are more informative, but remain scarce. We here described the first Cenozoic Lauraceae flower of Asia and confirmed the presence of Cryptocarya in the Miocene Zhangpu flora (Fujian Province, south-eastern China) based on an amber inclusion. We scanned the specimen using synchrotron radiation-based micro-computed tomography (SRμCT) and then compared the fossil with extant flowers of the genus. The present fossil flower is small, bisexual, and polysymmetric, with a whorled and trimerous perianth and androecium along with a hypanthium around the gynoecium. The perianth comprises six undifferentiated tepals, the androecium consists of nine stamens and three innermost staminodes, and the gynoecium of a single carpel with a superior, unilocular (and uniovulate) ovary. Our study also shows that the fossil shares an unusual position of the typical staminal glands and a short androecial tube on the rim of the hypanthium with at least one extant Australian species of Cryptocarya, which have not been reported before. Nowadays, Lauraceae are still present in tropical to subtropical regions, mostly in American and Asian rainforests. The discovery of many Lauraceae leaf fossils in Zhangpu, as well as the amber flower of this study, is consistent with the current reconstruction of the amber source environment as a megathermal seasonal rainforest during the Mid-Miocene

The mid-Miocene Zhangpu biota reveals an outstandingly rich rainforest biome in East Asia

During the Mid-Miocene Climatic Optimum [MMCO, ~14 to 17 million years (Ma) ago], global temperatures were similar to predicted temperatures for the coming century. Limited megathermal paleoclimatic and fossil data are known from this period, despite its potential as an analog for future climate conditions. Here, we report a rich middle Miocene rainforest biome, the Zhangpu biota (~14.7 Ma ago), based on material preserved in amber and associated sedimentary rocks from southeastern China. The record shows that the mid-Miocene rainforest reached at least 24.2°N and was more widespread than previously estimated. Our results not only highlight the role of tropical rainforests acting as evolutionary museums for biodiversity at the generic level but also suggest that the MMCO probably strongly shaped the East Asian biota via the northern expansion of the megathermal rainforest biome. The Zhangpu biota provides an ideal snapshot for biodiversity redistribution during global warming

Bilobate leaves of Bauhinia (Leguminosae, Caesalpinioideae, Cercideae) from the middle Miocene of Fujian Province, southeastern China and their biogeographic implications

Background: Morphological and molecular phylogenetic studies suggest that the pantropical genus Bauhinia L. s.l. (Bauhiniinae, Cercideae, Leguminosae) is paraphyletic and may as well be subdivided into nine genera, including Bauhinia L. s.s. and its allies. Their leaves are usually characteristic bilobate and are thus easily recognized in the fossil record. This provides the opportunity to understand the early evolution, diversification, and biogeographic history of orchid trees from an historical perspective under the framework of morphological and molecular studies. Results: The taxonomy, distribution, and leaf architecture of Bauhinia and its allies across the world are summarized in detail, which formed the basis for classifying the bilobate leaf fossils and evaluating the fossil record and biogeography of Bauhinia. Two species of Bauhinia are described from the middle Miocene Fotan Group of Fujian Province, southeastern China. Bauhinia ungulatoides sp. nov. is characterized by shallowly to moderately bilobate, pulvinate leaves with shallowly cordate bases and acute apices on each lobe, as well as paracytic stomatal complexes. Bauhinia fotana F.M.B. Jacques et al. emend. possesses moderately bilobate, pulvinate leaves with moderately to deeply cordate bases and acute or slightly obtuse apices on each lobe. Conclusions: Bilobate leaf fossils Bauhinia ungulatoides and B. fotana together with other late Paleogene - early Neogene Chinese record of the genus suggest that Bauhinia had been diverse in South China by the late Paleogene. Their great similarities to some species from South America and South Asia respectively imply that Bauhinia might have undergone extensive dispersals and diversification during or before the Miocene. The fossil record, extant species diversity, as well as molecular phylogenetic analyses demonstrate that the Bauhiniinae might have originated in the Paleogene of low-latitudes along the eastern Tethys Seaway. They dispersed southwards into Africa, migrated from Eurasia to North America via the North Atlantic Land Bridge or floating islands during the Oligocene. Then the genus spread into South America probably via the Isthmus of Panama since the Miocene onward, and underwent regional extinctions in the Boreotropics of mid-high-latitudes during the Neogene climatic cooling. Hence, Bauhinia presently exhibits a pantropical intercontinental disjunct distribution

Data from: The early history of Annonaceae (Magnoliales) in Southeast Asia suggests floristic exchange between India and Pan-Indochina by the late Oligocene

The collision between India and Eurasia in the mid‐Palaeogene facilitated terrestrial floristic exchange. However, due to the complexity of this geological event and scarcity of fossil record, the plant migration patterns between the two plates are still highly debated. In this study, we focus on the Oligocene floristic exchange between India and Pan‐Indochina mainly based on a carpological study of Annonaceae, an emblematic family unique in its pantropical distribution and frugivore‐based dispersal strategy. A new seed species, Anonaspermum orientalis sp. nov., is described from the upper Oligocene Yongning Formation of Guangxi, southern China. The species represents the earliest known occurrence of this family in Pan‐Indochina. The specimens are characterized by ovate–elliptic seed shape, thicker seed testa, two‐lobed organization, lamelliform rumination and an obvious cone‐like plug. The palaeobiogeographical reconstruction of Annonaceae indicates that the most parsimonious dispersal scenario for the annonaceous taxon from the late Oligocene of China is the Out‐of‐India route, in parallel with other plant genera inferred to have migrated between India and Pan‐Indochina during that period

Oligocene Koelreuteria (Sapindaceae) from the Lunpola Basin in central Tibet and its implication for early diversification of the genus

Fossils are critical for understanding the uplift history of the Tibetan Plateau and its impact on the diversity and diversification of living organisms in Eurasia. However, well-preserved fossils, especially plant megafossils are rare in the plateau. In this paper, we describe two species of Koelreuteria, namely K. lunpolaensis sp. nov. and K. miointegrifoliola, based on exquisitely preserved capsular valves from the late Oligocene of the Lunpola Basin, central Tibet. Koelreuteria lunpolaensis is distinguishable from all extant and fossil species of the genus in the strongly asymmetric form of the capsular valves, the emarginate or lobed apex of the valves, and zigzag lateral veins that are tapering towards the margin of the valves, and is considered to represent an extinct lineage of the genus. Koelreuteria miointegrifoliola is most similar to K. bipinnata-type group of extant Koelreuteria. The diverse Koelreuteria confirms a warm and humid environment with a low elevation in central Tibet during the late Oligocene based on their modem distributions. Fossil evidence indicates that the Tibetan Plateau was a center for diversity and diversification of Koelreuteria in the Oligocene/Miocene. It also suggests that Tibet might also serve as a refugium for the K. bipinnata-type group in the late Oligocene

Appendix S2 Fossil records of Annonaceae

Appendix S2 Fossil records of Annonacea

Fossil flowers from Miocene Zhangpu amber (China)

The Miocene Zhangpu amber from China represents one of the world’s richest amber biotas with more than13 000 inclusions of arthropods, gastropods, plants and fungi1. Arthropods are the most common organismsand have already been intensively studied, whereas seed plant inclusions have not been investigated in detailyet. However, these plant inclusions are an important key to gain new insights into the vegetation and plantdiversity of the amber source area, as well as the palaeoecological context of all the invertebrate inclusions.Here, we present the first detailed studies of seed plant inclusions from Zhangpu amber, comprising fourangiosperm flowers. Since their external features were not sufficient for identification and key characterswere hidden, we analysed the fossils using synchrotron radiation-based micro-computed tomography(SRμCT). This non-destructive technique allowed visualizing inner floral organs that were not accessible usingstandard light microscopy (Fig. 1), and essential for taxonomic identifications. The morphological analysis ofthe fossil inclusions indicate that the flowers show most similarities to modern Canarium (Burseraceae2),Cryptocarya (Lauraceae) and Byttneria (Malvaceae), and may represent new fossil species. In addition, theyare the first fossil flowers of those genera, which nowadays occur in pantropical regions of Southeast Asiawhere they are typical components of tropical rainforests.These flower inclusions thus provide new insights not only into the palaeoflora diversity of the Zhangpuamber forest but also further support its current interpretation as a megathermal seasonal rainforest.Moreover, our study emphasizes the great benefit of using X-ray based methods for analysing plant inclusionsin amber