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Albizia, a diverse tree genus, occupies monsoonal warm, humid rain forests in tropical and subtropical regions. We recovered a well-preserved compound fossil leaf and two fossil fruits of Albizia (Fabaceae) from the latest Neogene (Rajdanda Formation: Pliocene) sediments of Jharkhand of Chotanagpur Plateau, eastern India. On the basis of the architectural features of the fossil leaf, a new species is established as A. mahuadanrensis Hazra, Hazra and Khan, n. sp., characterised by a bipinnate, compound leaf having a rachis bearing opposite, asymmetrically ovate to sub-rhomboid leaflets, pulvinus on leaflet petiolule and brochiodromous secondary veins. Based on both morphological and anatomical characters of the fossil fruits, A. palaeoprocera Hazra, Hazra and Khan, n. sp. is erected, characterised by flattened to broadly linear shaped, wingless fruits; ovate-elliptic shaped seed chambers having ellipsoidal seeds in one series; irregularly polygonal to rectangular epidermal cells with oblique end walls and randomly oriented, scattered, paracytic stomata. Analysis of Albizia fossil occurrences indicates that the legume taxon was common in Neogene forests of India and elsewhere. The present-day distribution of the closely affiliated modern species of the fossil taxa indicates a warm and humid tropical environment during the time of deposition. We also review the biogeographic history of Albizia in India and other Asian countries.

Evidence of predatory marks on fossil leaf remains provides a unique window into ecological and evolutionary associations of the past, but finding both damage and the phytophagous insects causing that damage pattern in the same fossil specimen is a very rare phenomenon. Normally, caterpillars have little fossilization potential because of their delicate structure, but here, we present the first fossil evidence of leaf-feeding caterpillars, along with their characteristic feeding patterns, on the surface of diverse angiosperm leaf remains recovered from the latest Neogene (Pliocene, Rajdanda Formation) sediments of Chotanagpur Plateau, eastern India. This provides a rare direct insight into past plant-insect interaction, allowing us to identify, with confidence, the relationship between leaf damage and the perpetrator. The present finding also reveals that caterpillar-plant relationships and their feeding strategies seen today also existed during the Pliocene.

After India separated from Gondwana, its 9000 km northward voyage from the Southern Hemisphere to its modern position joined with Eurasia took 160 million years. During that journey, India experienced a range of climatic conditions due to secular climate variations and its changing latitudinal position. Documenting India's climate during its trans-equatorial journey allows us to sample climate across the low latitudes, at a time when global temperatures were exceptionally high, such as we might experience in the future. Here, we reconstruct, quantitatively, the palaeoclimate of India during its voyage, focussing on the latest Maastrichtian–earliest Danian, late Paleocene, early Eocene and late Oligocene timeslices. We exploit the relationship between fossil leaf form and climate and use the Climate-Leaf Analysis Multivariate Program to reconstruct 24 individual palaeoclimate parameters, while fossil leaf traits also allow us to identify different monsoon types. We find that throughout the Paleogene India persistently experienced a monsoon climate similar to that of modern Indonesia-Australia; a monsoon system that exists today primarily as a function of seasonal trans-equatorial migrations of the Inter-tropical Convergence Zone (ITCZ). The reconstructed near-equatorial thermal regime of India was cooler, and showed a greater seasonal temperature variation than at similar latitudes today, suggesting a wider seasonal latitudinal migration of the ITCZ throughout the Paleogene. Leaf traits showing adaptation to the South Asia Monsoon only developed after the end of the Paleogene.

The West Kunlun region forms the northern margin of the Tibetan Plateau, and sedimentation in this region contributed to plateau formation and its northwards expansion, as well as the development of central Asian aridification. However, the stratigraphic dating framework in this region has been ambiguous, hampering the understanding of both tectonic and environmental evolution. Here, palynological analysis was performed on the Xialafudie Formation in the West Kunlun region. Together with the palynological assemblage and megafossils found in the study section, as well as regional stratigraphic comparison, we conclude that the Xialafudie Formation was deposited during the Pliocene, and not Early Cretaceous as previously reported. The palynological assemblage of the section is mainly composed of drought-tolerant herbs and shrubs, and the percentage of conifers and broadleaved trees is very low, indicating that a dry and cold environment prevailed in the West Kunlun region during the Pliocene. Comprehensively analysed palynological data from the Tarim Basin and its surroundings show that aridification intensified in this part of central Asia during the Pliocene, as a result of long-term global cooling and regional tectonism.

In situ preservation of fossil insect damage in plant fossils is an excellent tool to study the coevolution of flora and fauna through geological time, but finding both damage and the insect causing that damage in the same specimen is a very rare phenomenon. Galling is a common form of angiosperm leaf damage, which can be regarded as a kind of extended phenotype of the causal insects, essentially the gall midges, but galls usually lack remains of the insects themselves. Here we report the in situ occurrence of a gall midge (Insecta, Diptera, Cecidomyiidae) as well as its pupal exuviae on the abaxial cuticular surface of fossilized leaf cuticle fragments of Fabaceae leaves (cf. Albizia) that also bear galls, recovered from the latest Neogene (Rajdanda Formation, Pliocene) sediments of the Chotonagpur Plateau, Jharkhand, northeastern India. This Pliocene gall midge features well-preserved legs, segmented antenna with distinct and enlarged scape, elongate curved setae, and longer than broad terminal plate of the ovipositor lamellae. The in situ presence of a gall midge on a host fabaceous leaf cuticle indicates the existence of a host-ectoparasite relationship in the ancient warm and humid tropical monsoon-influenced forests of eastern India during the Pliocene. This is the first authentic fossil record of an in situ phytophagous insect of Cecidomyiidae from India, as well as southeast Asia. Although the identification of the recovered phytophagous insect associated with the fossil leaf cuticle is only possible to family level, this find reveals that such plant-insect relationships existed in the Pliocene of eastern India.

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Premise of research. The fossil record of Rhamnaceae is geographically widespread and ranges from the Cretaceous to the Pleistocene, but only a few fossil fruits, namely, Ventilago engoto from the ...

The extinct genus Limnobiophyllum (Araceae) has been considered a tentative link between the Aroideae and Lemnoideae subfamilies of Araceae. General understanding of morphological character evoluti...

The biodiversity history on the Qinghai-Tibetan Plateau (QTP) has remained unclear for a long time. Recent palaeobotanical investigations provide opportunities for revealing the phytogeographic history on the QTP in deep time and for testing phylogeographic hypotheses. Lagokarpos is an extinct genus with unknown modern affinities. It is easily distinguished by its fruits which have two long wings and an elliptical fruit body. Previously, Lagokarpos fossils have only been found from North America and Germany, ranging from the latest Paleogene to early middle Eocene. Recently, we found fossil fruits of this genus from the Niubao Formation, near Bangoin County in the central QTP. A new species, namely Lagokarpos tibetensis H. Tang, T. Su & Z.K. Zhou sp. nov. is described. This is the first fossil record of the genus in Asia. The occurrence of L. tibetensis indicates a close floristic linkage between the QTP and other floras in the Northern Hemisphere during the Paleogene. Meanwhile, according to the floristic assemblages, we suggest the central QTP experienced a tropical or subtropical humid climate during that period.

A substantial biotic interchange took place between Gondwanan India and Laurasia immediately following the India-Eurasia collision. Located just north of the collision zone, the role of the Tibetan Plateau in the geographic interchange of biota is still unknown because lack of fossil evidence. Here, well-preserved samara fossils of Ailanthus (the family Simaroubaceae) are described from the Lunpola and Nima basins, central Tibetan Plateau, ranging in age from the latest Paleocene to the Late Oligocene. These fossils are the largest samara fossils of this genus found so far. Characteristics such as the main ventral vein located in the intramarginal part of the samara, and the stylar scar located on the midline of the seed suggest that they represent a new species, which we herein name Ailanthus maximus J. Liu, T. Su et Z.K. Zhou, sp. nov. These findings greatly expand the known spatial distribution of Ailanthus in the Paleogene, and suggest that the Tibetan Plateau has played an important role in the migration of biota between Gondwanan India and the Northern Hemisphere. In addition, A. maximus is morphologically similar to A. triphysa, a living species which is naturally distributed in tropical and subtropical regions in Southeast Asia at elevation no more than 600 m, indicating a tropical or subtropical lowland environment in the central Tibetan Plateau during the latest Paleocene to Late Oligocene. Moreover, together with previous paleoaltimetric estimates, we propose that tropical or subtropical lowlands along the Bangong-Nujiang Suture Zone and the Yarlung-Zangpo Suture Zone existed in some parts of the Tibetan Plateau during the Paleogene only obtained their current elevation during the Neogene.

The Arctic is warming faster than anywhere else of comparable size on Earth, impacting global climate feedbacks and the Arctic biota. However, a warm Arctic is not novel. The Late Cretaceous fossil record of the region enables a detailed reconstruction of polar environmental conditions, and a thriving extinct ecosystem, during a previous 'hothouse’ global climate. Using leaf form (physiognomy) and tree ring characteristics we reconstruct Cenomanian to Coniacian polar thermal and hydrological regimes over an average annual cycle at eight locations in NE Russia and northern Alaska. A new high spatial resolution (∼1 km) WorldClim2 calibration of the Climate Leaf Analysis Multivariate Program (CLAMP) yields results similar to, but often slightly warmer than, previous analyses, but also provides more detailed insights into the hydrological regime through the return of annual and seasonal vapour pressure deficit (VPD), potential evapotranspiration (PET) estimates and soil moisture, as well as new thermal overviews through measures of thermicity and growing degree days. The new results confirm the overall warmth of the region, particularly close to the Arctic Ocean, but reveal strong local differences that may be related to palaeoelevation in the Okhotsk–Chukotka Volcanogenic Belt in NE Russia. While rainfall estimates have large uncertainties due to year-round wet soils in most locations, new measures of VPD and PET show persistent high humidity, but with notably drier summers at all the Arctic sites.

In this study, we developed a tree-ring δ18O chronology of Abies delavayi from Diancangshan (25°41′N, 100°06′E), in the Hengduan Mountains of Southwest China, spanning 205 years (1810–2014 CE). Tree-ring δ18O from Abies delavayi showed the highest negative correlation with relative humidity in the spring (r = −0.59, P

Fossil leaf floras, from the latest Miocene-Pliocene Siwalik Group exposed in Bhutan, sub-Himalaya, are subjected to a CLAMP (Climate Leaf Analysis Multivariate Program) analysis using a high-resolution gridded climate calibration. The CLAMP analysis of 27 different morphotypes of fossil leaves indicates a mean annual temperature (MAT) of 24.1 °C ± 2.8 °C; a cold month mean temperature (CMMT) of 18.9 °C ± 4 °C and a warm month mean temperature (WMMT) of 27.8 °C ± 3.3 °C. The analysis also suggests a weak monsoonal climate (the monsoon index, MSI 46.7; present MSI 52) with growing season precipitation (GSP) of 1819 ± 916 mm (present GSP 2490 mm). Here we also compare palaeoclimate estimates of the latest Miocene-Pliocene Siwalik Group flora from Bhutan (c. 6 to 3.8 Ma) with those of previously investigated Siwalik Group floras from the Miocene-Pleistocene of Arunachal, India and Miocene Siwalik floras of Darjeeling, India which characterise the monsoon signature at the time of deposition. Since all the Siwalik floras of the eastern Himalaya (Darjeeling and Arunachal Pradesh) spanning the mid-Miocene to Pleistocene yield almost the same values we suggest that overall the eastern Himalayan Siwalik climate appears to have been remarkably uniform over the past 15 million years. The MAT result of the Bhutan Siwalik flora differs by just 0.6 °C from Arunachal and 1.2 °C from Darjeeling Siwalik floras. For all Siwalik fossil assemblages, WMMTs, CMMTs and LGSs (length of the growing season) are similar and consistent (WMMTs around 28 °C, CMMTs around 18 °C and LGSs around 12 months). Similarly, the mean annual relative humidity (RH) and specific humidity (SH) appear to have been uniformly around 80% and 14 g/kg respectively throughout the Neogene of the eastern Himalayan Siwaliks. Changes in the monsoon index suggest that in both Bhutan and Arunachal sub-Himalaya, there has been little change in the intensity of the monsoon since mid-Miocene time, while further west in the Darjeeling area precipitation seasonality has increased since the mid-Miocene.

Information on whether tyloses in fossil angiospermic plants form specifically in response to infestation with pathogenic fungi has been lacking so far, and thus the evolutionary history of tylosis formation as a physical restraint strategy against the advancing fungi remains unresolved. Our study addresses this knowledge lacuna. Carbonized woods were recovered from the upper part of the Siwalik succession (Kimin Formation: late Pliocene to early Pleistocene) of Arunachal Pradesh, eastern Himalaya. Samples from different portions of the wood remains were prepared by using standard thin sectioning techniques and studied under transmitted light compound and scanning electron microscopes. The Plio-Pleistocene wood remains are attributed to Gmelina arborea Roxb. (Lamiaceae) as Gmelina siwalika Khan, Bera M et Bera S, sp. nov. Numerous well-preserved tyloses were found mainly in the central heartwood region of the fossil wood. Rare fungal remains indicative of early-stage colonization are characterized by septate fungal hyphae extending through the vascular ray system within the secondary xylem, and fungal spores. As tyloses are present in large numbers and formed before the spread of fungal remains, they served as an effective physical restraint to the spread of the fungi. We conclude that tylosis formation contributed to an antagonistic relationship between pathogenic fungi and Gmelina plant in Neogene paleoecosystems of the eastern Himalaya. This report also demonstrates that the development of this histological protrusion has been a significant process in woody plants since Cenozoic.

A comprehensive morphotaxonomical evaluation of diverse angiospermic dicotyledonous leaf impressions recovered from the middle part of the Siwalik succession (Subansiri Formation: Pliocene) of Arunachal Pradesh, eastern Himalaya, India, shows that the leaf remains are comparable to modern Glochidion J. R. Forst. and G. Forst. (Phyllanthaceae), Bauhinia L., Callerya Endl. (Fabaceae), Mitragyna Korth. (Rubiaceae), Beilschmiedia Nees (Lauraceae), Uvaria L. (Annonaceae), Neolamarckia Bosser (Rubiaceae), Sorindeia Thouars (Anacardiaceae), Lagerstroemia L. (Lythraceae), and Premna L. (Lamiaceae). Among these taxa, seven species are new to the Neogene floras of the Indian subcontinent. Analyses of the floral assemblage, with respect to the present-day distribution pattern of modern equivalent taxa and the physiognomic characters of the recovered fossil leaves, suggest that a tropical evergreen forest was growing in a warm humid climate in the region at the time of deposition. This qualitative climatic data is also corroborated by our previously published quantitative data obtained from a CLAMP (climate leaf analysis multivariate program) analysis on the middle Siwalik floral assemblage. The presence of some Southeast Asian elements in the fossil assemblage provides clear evidence of free exchange of taxa across southern Asia in the Pliocene.

Foliage fossils of a fig, Ficus microtrivia J. Huang et Z. K. Zhou sp. nov. (Moraceae) is reported from early to middle Miocene lacustrine sediments in the Wenshan Basin, Yunnan, southwestern China. The leaf architecture and preserved exocrine veinlet glands on the fossils are irrefutable evidence for genus-level systematic assignment. Four venation patterns in the extant genus Ficus L. are summarised and established, subgenus and species level comparisons of the fossils are applied according to this framework. The nearest living relative of the new fossil-species is Ficus trivia Corner of Subgen. Ficus, a species restricted to the karst shrub habitat in southern China and northern Vietnam. Together with other elements of the fossil assemblage, this species indicates that open, shrubby vegetation on limestone similar to that in the same region today, already existed in the early to middle Miocene.

Indian Cenozoic deposits contain well-preserved diverse angiosperm leaf assemblages, but galling, a common form of angiosperm leaf damage in modern tropical forests, has not been well-documented. Here we report insect herbivory on diverse angiosperm fossil leaf specimens from Pliocene (Rajdanda Formation) sediments of the Chotanagpur Plateau, eastern India, revealing that galling was the most common form of folivory in the latest Neogene monsoon-adapted tropical forests of eastern India. Diverse well-preserved galls are described on the basis of their size, shape and position on the host angiosperm leaf remains. Nine gall damage types (DT 32, DT 33, DT 34, DT 80, DT 83, DT 85, DT 110, DT 120, and DT 144) are identified. They are compared with extant galls and the probable gall inducers making morphologically similar galls on related host tropical plant species of Ficus, Mangifera, Albizia, Galactia, Ziziphus, Hylodesmum, Adina, and Psidium. The gall producers belong to the insect orders Orthoptera, Hemiptera, Hymenoptera, Coleoptera, Lepidoptera, and Diptera (Cecidomyiidae). Although the detailed morphology of the phytophagous insects associated with the recovered fossil leaves is unknown, our findings indicate that many modern plant-insect relationships were likely established by the Pliocene. The reconstructed warm, humid Pliocene climate with a weak monsoon seasonality was conducive to extensive galling activity during this time.

Our understanding regarding the onset and development of the modern South Asia monsoon (SAM) is still incomplete due to its complex nature and differing views about its relationship with major orographic features such as the Himalaya and Tibetan Plateau. Climate data derived from some terrestrial and marine sediments from the Neogene suggests the onset and intensification of the SAM to a near-modern state occurred during the Miocene, while modelling and other terrestrial proxies point to a much earlier origin for the proto-East Asia monsoon (EAM) and proto-SAM. Angiosperm leaves, particularly dicot leaves, provide a good indication of prevailing climatic conditions as a result of key adaptations in their leaf structure. Here we use Climate Leaf Analysis Multivariate Program (CLAMP) in conjunction with general circulation models to decode the Lower (~13–11 Ma) and Middle (9.5–6.8 Ma) Siwalik climate signal inherent in the physiognomy of fossil leaves. The reconstructed climate data indicates that the Middle Siwalik was warmer and wetter than the Lower Siwalik, particularly in the cooler part the year. The leaf physiognomy of Lower and Middle Siwalik assemblages is indistinguishable to that of the modern leaf assemblages, which are influenced by today's SAM climate. This shows that the SAM was already well established as an independent domain during the late middle Miocene (~13–11 Ma) and has remained nearly the same from the perspective of leaf adaptations since then. A quantitative monsoon intensity index indicates an intensified monsoon during the late Miocene (9.5–6.8 Ma), a finding replicated by climate modelling.

Significance The ancient topography of the Tibetan Plateau and its role in biotic evolution are still poorly understood, mostly due to a lack of fossil evidence. Our discovery of ∼47-Mya plant fossils from a present elevation of 4,850 m in central Tibet, diminishes, significantly, that lack of knowledge. The fossils represent a humid subtropical vegetation and some of the 70 different plant forms show affinity to Early-Middle Eocene floras in both North America and Europe. Using leaf architecture, we calculate that the forest grew at ∼1,500-m elevation within an east–west trending valley under a monsoonal climate. Our findings highlight the complexity of Tibet’s ancient landscape and emphasize the importance of Tibet in the history of global biodiversity., Tibet’s ancient topography and its role in climatic and biotic evolution remain speculative due to a paucity of quantitative surface-height measurements through time and space, and sparse fossil records. However, newly discovered fossils from a present elevation of ∼4,850 m in central Tibet improve substantially our knowledge of the ancient Tibetan environment. The 70 plant fossil taxa so far recovered include the first occurrences of several modern Asian lineages and represent a Middle Eocene (∼47 Mya) humid subtropical ecosystem. The fossils not only record the diverse composition of the ancient Tibetan biota, but also allow us to constrain the Middle Eocene land surface height in central Tibet to ∼1,500 ± 900 m, and quantify the prevailing thermal and hydrological regime. This “Shangri-La”–like ecosystem experienced monsoon seasonality with a mean annual temperature of ∼19 °C, and frosts were rare. It contained few Gondwanan taxa, yet was compositionally similar to contemporaneous floras in both North America and Europe. Our discovery quantifies a key part of Tibetan Paleogene topography and climate, and highlights the importance of Tibet in regard to the origin of modern Asian plant species and the evolution of global biodiversity.

The Tibetan Plateau was built through a succession of Gondwanan terranes colliding with Asia during the Mesozoic. These accretions produced a complex Paleogene topography of several predominantly east–west trending mountain ranges separated by deep valleys. Despite this piecemeal assembly and resultant complex relief, Tibet has traditionally been thought of as a coherent entity rising as one unit. This has led to the widely used phrase ‘the uplift of the Tibetan Plateau’, which is a false concept borne of simplistic modelling and confounds understanding the complex interactions between topography climate and biodiversity. Here, using the rich palaeontological record of the Tibetan region, we review what is known about the past topography of the Tibetan region using a combination of quantitative isotope and fossil palaeoaltimetric proxies, and present a new synthesis of the orography of Tibet throughout the Paleogene. We show why ‘the uplift of the Tibetan Plateau’ never occurred, and quantify a new pattern of topographic and landscape evolution that contributed to the development of today’s extraordinary Asian biodiversity.

Dipterocarpaceae, a tropical plant family that forms a major component of low-lying rainforests in Southeast Asia, is represented by a large number of fossils from the Cenozoic sedimentary successions of India, but the origin and antiquity of this family has been actively debated. The earliest reliable dipterocarp megafossils so far reported in India come from Eocene (34–23 Ma) sediments of the Cambay Basin of western India and in Southeast Asia from Eocene (34–23 Ma) sediments within China. More recently, pollen attributable to the family was recovered from Maastrichtian sediments in India, but because pollen is highly durable, can be transported over long distances and offers only low taxonomic resolution, more definitive evidence is required to demonstrate, unequivocally, that the Dipterocarpaceae were in India prior to its contact with Eurasia early in the Paleogene. The Late Cretaceous (Maastrichtian) leaf fossils documented here have an affinity with the extant genus Dipterocarpus (family Dipterocarpaceae) and come from the Mandla Lobe Deccan Intertrappean Beds of Central India. They provide compelling evidence that this tropical rain forest element was present in India during Chron 29R, which spans the K-Pg transition, and when the bulk of the subcontinent was still in the Southern Hemisphere. We suggest that only later did their dispersal to Southeast Asia occur, consistent with the “Out-of-India” hypothesis. These fossil leaves represent the earliest reliable fossil record of the Dipterocarpaceae and, in particular, Dipterocarpus.

The Paleogene environment of today's semi-arid and arid Central Asia is poorly quantified and knowledge of the paleoelevation of northern Tibet remains elusive, yet both are crucially important for understanding inter-relationships between growth of the Tibetan Plateau and Asian monsoon development. Here, we apply the Climate-Leaf Analysis Multivariate Program (CLAMP) and moist enthalpy method to the newly discovered early Oligocene (30.8 Ma) fossil leaves from the Qaidam Basin, to reconstruct quantitatively the paleoclimate and paleoelevation of this critical part of northern Tibet. We find the Qaidam Basin floor vegetation was likely at ∼3.3 ± 1.4 km in the early Oligocene, similar to that of the present basin floor but higher than the rising Himalaya at that time, and experienced a temperate, moderately wet climate. Near-freezing (1.4 ± 3.5 °C) winters accompanied cool summers (∼23 ± 2.9 °C). Annual precipitation likely exceeded 1000 mm (growing season precipitation of 1229 ± 643 mm) with subdued (non-monsoonal) seasonality in which summers were drier than winters. This finding challenges geodynamic models that envisage a Miocene or later uplift of northern Tibet and progressive uplift from the south.

Silicified fossil legume woods of Cynometroxylon Chowdhury & Ghosh collected from the Neogene (late Miocene) sediments of the Bengal Basin, eastern India, exhibit fungal decay seldom found in the fossil record. The wood possesses numerous perforate areas on the surface that seem to be the result of extensive fungal activity. In transverse section, the decayed areas (pockets) appear irregular to ellipsoidal in outline; in longitudinal section these areas of disrupted tissue are somewhat spindle-shaped. Individual pockets are randomly scattered throughout the secondary xylem or are restricted to a narrow zone. The aforesaid patterns of decay in fossil wood show similarities with that of white rot decay commonly produced by higher fungi, specifically basidiomycetes and ascomycetes. The host fossil wood harbors abundant ramifying and septate fungal hyphae with knob like swellings similar to pseudoclamps in basidiomycetes, and three-celled conidia-like reproductive structures. This record expands our current knowledge of wood decaying fungi-host plant interaction in the Neogene tropical forests of Peninsular India.

The often-used phrase ‘the uplift of the Tibetan Plateau’ implies a flat-surfaced Tibet rose as a coherent entity, and that uplift was driven entirely by the collision and northward movement of India. Here, we argue that these are misconceptions derived in large part from simplistic geodynamic and climate modeling, as well as proxy misinterpretation. The growth of Tibet was a complex process involving mostly Mesozoic collisions of several Gondwanan terranes with Asia, thickening the crust and generating complex relief before the arrival of India. In this review, Earth system modeling, paleoaltimetry proxies and fossil finds contribute to a new synthetic view of the topographic evolution of Tibet. A notable feature overlooked in previous models of plateau formation was the persistence through much of the Cenozoic of a wide east–west orientated deep central valley, and the formation of a plateau occurred only in the late Neogene through compression and internal sedimentation.

Mastixioids in the family Cornaceae, are presently native only in limited areas of Asia, they have rich fossil fruit record in Cenozoic sediments of Europe and North America, but unfortunately none have been reported from Cenozoic sediments of India and Asia until now. Here, we report the occurrence of leaf remains (both impression and compression) along with carbonised fruits, resembling morphologically and anatomically those of the extant endemic species Mastixia arborea C.B. Clarke. Our materials were recovered from the middle Miocene to early Pleistocene Siwalik sediments exposed around West Kameng and Papumpare districts in Arunachal Pradesh, eastern Himalaya. These new fossil materials confirm the existence of Mastixia in the Miocene-Pleistocene Siwalik forests in India. At present the modern analogue does not grow in the eastern Himalaya and is endemic to the tropical evergreen forests of the Western Ghats, situated at the same palaeolatitude as the fossil locality. Extinction from the entire eastern Himalaya and probable movement of this taxon to the Western Ghats is likely due to climate change in the area, related to the Himalayan Orogeny during Miocene–Pleistocene times. The disappearance of Mastixia from this area may be related to the gradual intensification of rainfall seasonality since the late Miocene. The recovery of this species and our earlier-described evergreen taxa from the same Siwalik time (Mio-Pleistocene), suggest the existence of tropical, warm and humid climatic conditions during the period of deposition. The leaf and fruit remains are here described as new species, namely Mastixia asiatica Khan, Bera M et Bera S, sp. nov. and Mastixia siwalika Khan, Bera M et Bera S, sp. nov. respectively. This report documents the first fossil record of Mastixia leaf remains using both macro and micromorphological characters. We also review the historical phytogeography, and highlight the phytogeographic implication of, the mastixioids.

Trapa (water chestnut or water caltrop) is a genus of annual free-floating plants mostly native to Africa and Eurasia and included in the family Lythraceae. The genus only contains 10 species today but has a large number of species in the Neogene record, mainly based on fruits but also on the occurrence of pollen grains. In China, several species have previously been recorded from the Neogene, but few have a detailed description. Here we describe a new species of fruit from the Pliocene of the Sanying Formation, Yangjie coalmine, western Yunnan, namely Trapa sanyingensis sp. nov., based on the following characters: the size of the fruit, the relatively long upper horns, the well-developed and triangular lower horns, the well-developed tubercles between the lower and upper horns, and a long and wide neck bearing hairs without a corona. In addition, pollen grains belonging to Sporotrapoidites cf. weiheensis were uncovered from the same sediment and have the following characters: tricolpate, obtuse triangular shape in polar view, and three meridional crests covering the apertures. T. sanyingensis sp. nov. shows a close morphological similarity to the Miocene species Trapa chengsenii from the Yunnan and to the modern species Trapa natans. The pollen grains also closely resemble those of Trapa natans. The occurrence of T. sanyingensis sp. nov. suggests that the sedimentary site corresponds to open and shallow water with a water temperature above 20 °C during the growing season.

Monsoonal climates at low latitudes (< 32°N) are an inevitable consequence of seasonal migrations of the Inter-tropical Convergence Zone (ITCZ), but the character of these monsoons depends on continental configuration, orographic expression and the strength of Hadley circulation. To explore the evolution of monsoon systems across southern Asia we compare climate signatures archived in ten Paleogene floras from northern India, Tibet and southern China, occupying low palaeolatitudes at a time of extreme global warmth and elevated CO2. Fossil leaf form reveals that under such 'hothouse' conditions megathermal early Eocene to earliest Miocene forests were exposed to strong monsoonal climates typical of those experienced today arising from annual migrations of the ITCZ, possibly enhanced by a lower equator-to-pole temperature gradient. Throughout the Paleogene an elevated Tibetan highland produced no discernable modification of this ITCZ monsoon, although rainfall seasonality similar to that of the modern South Asia Monsoon (SAM) is observed in northern India as early as the beginning of the Eocene, despite its near-equatorial palaeoposition. In South China rainfall seasonality increased progressively achieving modern monsoon-like wet season/dry season precipitation ratios by the early Oligocene. Despite evidencing weak rainfall seasonality overall, fossil leaves from South China have exhibited monsoon-adapted morphologies, comparable to those seen in today's Indonesia-Australia Monsoon, for at least 45 million years. Together, the Indian and South China fossil leaf assemblages show that the evolution of megathermal ecosystems across southern Asia has been influenced profoundly by monsoonal climates for at least the last 56 million years. The Paleogene ITCZ-driven monsoon system strongly impacted India as it transited the Equator likely eliminating Gondwanan taxa not able to adapt to seasonal precipitation extremes. Furthermore, powerful seasonally-reversing winds, and associated surface ocean currents, are likely to have facilitated two-way biotic transfer between India and Eurasia long before closure of the Tethys Ocean.

Although the Eocene-Oligocene climate transition marks a critical point in the development of the ‘icehouse’ global climate of the present little is known about this important change in the terrestrial realm at low latitudes. Our palynological study of the Shangcun Formation shows it to be early Oligocene in age: palyno-assemblages in the lower part of the formation indicate a cool interval dominated by conifer pollen in the earliest Oligocene followed by a warmer regime in the second half of the early Oligocene. To quantify middle Eocene to late early Oligocene climate conditions at low (~ 20°N) palaeolatitudes in southern Asia several thousand leaf fossil specimens from the Maoming Basin, southern China, were subjected to a multivariate (CLAMP) analysis of leaf form. For terrestrial palaeoclimate comparisons to be valid the palaeoaltitude at which the proxy data are obtained must be known. We find that leaves preserved in the Youganwo (middle Eocene), Huangniuling (late Eocene) and Shangcun (early Oligocene) formations were likely to have been deposited well above sea level at different palaeoelevations. In the Youganwo Formation fine-grained sediments were deposited at an altitude of ~ 1.5 km, after which the basin dropped to ~ 0.5 km by the time the upper Huangniuling sediments were deposited. The basin floor then rose again by 0.5 km reaching an altitude of approximately 1 km in which the Shangcun Formation fine-grained sediments were accumulated. Within the context of these elevation changes the prevailing climates experienced by the Youganwo, Lower Huangniuling, Upper Huangniuling and Shangcun fossil floras were humid subtropical with hot summers and warm winters, but witnessed a progressive increase in rainfall seasonality. By the early Oligocene rainfall seasonality was similar to that of the modern monsoonal climate of Guangdong Province, southern China. All floras show leaf physiognomic spectra most similar to those growing under the influence of the modern Indonesia-Australia Monsoon, but with no evidence of any adaptation to today's South or East Asia Monsoon regimes. The Upper Huangniuling Flora, rich in dipterocarp plant megafossils, grew in the warmest conditions with the highest cold month mean temperature and at the lowest altitude.

Here, we report fossil leaves, woods, and pollen grains comparable to Calophyllum L. (mainly to Calophyllum inophyllum L. and Calophyllum polyanthum Wall. ex Choisy) of Calophyllaceae from the upper (Kimin Formation, late Pliocene-early Pleistocene), middle (Subansiri Formation, Pliocene) Siwalik sediments of the Arunachal sub-Himalaya, and lower (Gish Clay Formation of Sevok Group; middle to late Miocene) Siwalik sediments of the Darjeeling foothills, eastern Himalaya. Their presence indicates a warm and humid tropical environment in the region during the period of Siwalik sedimentation. Considering all records of Calophyllum, it is suggested that Calophyllum was a frequent forest element throughout the period of Siwalik sedimentation during the Neogene (Miocene time). At present, C. polyanthum grows in the eastern Himalaya, but C. inophyllum is totally absent from north-eastern regions suggesting differential adaptability of these taxa to changing ecoclimatic conditions. Distinct climate change in the area, possibly related to the Himalayan Orogeny during Miocene–Pleistocene times, might have caused the disappearance of C. inophyllum from the entire eastern Himalaya and north-east Indian plains and a move to littoral/coastal and swampy forests of India and other adjoining south-east Asian regions, Polynesia, and the east coast of Africa. The past global distribution of Calophyllum is also discussed, and it is suggested that India may have been its primary centre of origin. This is the first time Cenozoic fossil leaves Calophyllum siwalikum Khan, R.A.Spicer & Bera, sp. nov. comparable to C. inophyllum are described using the both macro- and micromorphological characters.

We reconstruct the rise of a segment of the southern flank of the Himalaya-Tibet orogen, to the south of the Lhasa terrane, using a paleoaltimeter based on paleoenthalpy encoded in fossil leaves from two new assemblages in southern Tibet (Liuqu and Qiabulin) and four previously known floras from the Himalaya foreland basin. U-Pb dating of zircons constrains the Liuqu flora to the latest Paleocene (ca. 56 Ma) and the Qiabulin flora to the earliest Miocene (21- 19 Ma). The proto-Himalaya grew slowly against a high (similar to 4 km) proto-Tibetan Plateau from similar to 1 km in the late Paleocene to similar to 2.3 km at the beginning of the Miocene, and achieved at least similar to 5.5 km by ca. 15 Ma. Contrasting precipitation patterns between the Himalaya-Tibet edifice and the Himalaya foreland basin for the past similar to 56 m.y. show progressive drying across southern Tibet, seemingly linked to the uplift of the Himalaya orogen.

A 105 m early Eocene section exposed in the Gurha mine in the Nagaur-Ganganagar Basin, Rajasthan, India, archiving remains of equatorial vegetation at a time of extreme global warmth and close to the onset of the India-Eurasia collision, is investigated using palynostratigraphic and palynofacies analyses. Four palynozones e.g., Palmidites plicatus Singh, Botryococcus braunii Kützing, Triangulorites bellus Kar and Ovoidites ligneolus are identified stratigraphically on the basis of abundance of these pollen taxa over others. The occurrence of taxonomically highly diverse angiosperm pollen in all the four palynozones attests to an extremely rich near-coastal tropical flora subject to frequent wildfires under a strongly seasonal precipitation regime. Palynotaxa characteristic of these palynozones are widely distributed in other early Paleogene sediments of India. Sedimentary organic matter (structured terrestrial, biodegraded, amorphous, grey amorphous, resins, charcoal/black-brown debris and algal remains) recovered from mire and lacustrine sediments are of terrestrial origin, recording fluctuations in burial anoxia and salinity. Episodes of elevated salinity are due either to seepage of marine waters and/or a periodic excess of evaporation over precipitation at times when the depositional system was closed.

The relationship between plant form and climate has been recognised for more than two millennia, and the idea that fossils can indicate climate change was first recorded almost a thousand years ago. Here we review ways of using plant form to reconstruct, quantitatively, past climates, focussing on techniques that have been developed over the past century. We begin with the relationship between woody dicot leaf margins and temperature, and trace the development of the approach through to the modern multivariate tool known as Climate-Leaf Analysis Multivariate Program (CLAMP), which can derive 24 different climate parameters from 31 macroscopic leaf traits commonly preserved in leaf fossils. We review the complex inter-dependant correlations between leaf traits and climate, recognising that leaves develop and function as integrated systems, and that there is a selective premium on them being well adapted to their immediate climatic environment. We discuss different ways of understanding and decoding climate from leaf form in multidimensional trait space, and provide an over-view of CLAMP applications for tracking climate change, monsoon evolution, and in palaeoaltimetry, from the middle Cretaceous to the Pleistocene.

Here we study a well-preserved petrified palm stem from the latest Maastrichtian (Late Cretaceous) to earliest Danian (early Paleocene) sediments (c. 66–65 Ma old) of the Deccan Intertrappean Beds of Madhya Pradesh, Central India. We infer its systematic relationships and relevance to palm evolution. The significant anatomical attributes of the fossil include the presence of fibrovascular bundles (fvbs) with reniform dorsal fibrous sclerenchyma (dcap), 2 to > 4 metaxylem vessel elements in each fvb, lacunar ground parenchyma tissue, and centrifugal differentiation of the fibrous dcap parts of the fvbs. These features reveal a close resemblance to extant taxa of the wax palm subfamily Ceroxyloideae, now with a disjunct distribution in America, Australia, Madagascar and the Comoros. The Cretaceous stem is described here as Palmoxylon ceroxyloides Khan, Hazra et Bera, sp. nov. This is the oldest reliable occurrence of Ceroxyloideae in the fossil record. Present fossil evidence indicates that the sub-family was already present in India in the Late Cretaceous (Maastrichtian), about 10–15 million years before the collision of India with Eurasia. Post-collision the subfamily may have been dispersed to East Asia and then to North America via the Bering land bridge (BLB), finally reaching South America via the Isthmus of Panama link during the Miocene. However, the present-day distribution of Ceroxyloideae in Australia, Madagascar and Comoros may be explained by a historical long-distance dispersal (LDD) hypothesis.

The early Oligocene represents the beginning of the modern icehouse world. To better understand how vegetation and climate changed during this period, we reconstruct quantitively the early Oligocene vegetation and climate by analyzing fossil spore and pollen assemblages from Luhe basin, Yunnan Province, in southwestern China. The reconstructed paleoclimate using Bioclimatic Analysis shows that the mean annual temperature (MAT) ranged from 14.4 to 15.4 °C, the mean annual precipitation (MAP) was 1070.1–1297.8 mm, and the range of mean temperature of coldest quarter (MTCQ) was 6.7 to 7 °C, lower than that of the present day (9.3 °C). The reconstructed regional vegetation indicates a deciduous broadleaved forest mixed with evergreen broadleaved elements. Considering other Paleogene floras in Yunnan, deciduous broadleaved elements dominated in this area from the late Eocene to the early Oligocene. The paleoclimate reconstruction suggests that this vegetation composition may have been controlled mainly by cold winter temperatures.

The onset and development of the Asian monsoon systems is a topic that has attracted considerable research effort but proxy data limitations, coupled with a diversity of definitions and metrics characterizing monsoon phenomena, have generated much debate. Failure of geological proxies to yield metrics capable of distinguishing between rainfall seasonality induced by migrations of the Inter-tropical Convergence Zone (ITCZ) from that attributable to topographically modified seasonal pressure reversals has frustrated attempts to understand mechanisms underpinning monsoon development and dynamics. Here we circumvent the use of such single climate parameter metrics in favor of detecting directly the distinctive attributes of different monsoon regimes encoded in leaf fossils. Leaf form adapts to the prevailing climate, particularly under the extreme seasonal stresses imposed by monsoons, so it is likely that fossil leaves carry a unique signature of past monsoon regimes. Leaf form trait spectra obtained from fossils from Eocene basins in southern China were compared with those seen in modern leaves growing under known climate regimes. The fossil leaf trait spectra, including those derived from previously published fossil floras from northwestern India, were most similar to those found in vegetation exposed to the modern Indonesia–Australia Monsoon (I–AM), which is largely a product of seasonal migrations of the ITCZ. The presence of this distinctive leaf physiognomic signature suggests that although a monsoon climate existed in Eocene time across southern Asia the characteristics of the modern topographically-enhanced South Asia Monsoon had yet to develop. By the Eocene leaves in South Asia had become well adapted to an I–AM type regime across many taxa and points to the existence of a pervasive monsoon climate prior to the Eocene. No fossil trait spectra typical of exposure to the modern East Asia monsoon were seen, suggesting the effects of this system in southern China were a much later development.

The relationship linking leaf physiognomy and climate has long been used in paleoclimatic reconstructions, but current models lose precision when worldwide data sets are considered because of the broader range of physiognomies that occur under the wider range of climate types represented. Our aim is to improve the predictive power of leaf physiognomy to yield climate signals, and here we explore the use of an algorithm based on the general regression neural network (GRNN), which we refer to as Climate Leaf Analysis with Neural Networks (CLANN). We then test our algorithm on Climate Leaf Analysis Multivariate Program (CLAMP) data sets and digital leaf physiognomy (DLP) data sets, and compare our results with those obtained from other computation methods. We explore the contribution of different physiognomic characters and test fossil sites from North America. The CLANN algorithm introduced here gives high predictive precision for all tested climatic parameters in both data sets. For the CLAMP data set neural network analysis improves the predictive capability as measured by R-2, to 0.86 for MAT on a worldwide basis, compared to 0.71 using the vector-based approach used in the standard analysis. Such a high resolution is attained due to the nonlinearity of the method, but at the cost of being susceptible to 'noise' in the calibration data. Tests show that the predictions are repeatable, and robust to information loss and applicable to fossil leaf data. The CLANN neural network algorithm used here confirms, and better resolves, the global leaf form-climate relationship, opening new approaches to paleoclimatic reconstruction and understanding the evolution of complex leaf function.

Reconstructions of temperature and moisture regimes based on fossil leaves, combined with tree ring studies, detail the light regime, length of the growing season, and summer and winter temperatures of the Late Cretaceous Arctic. Such constraints have important implications for dinosaur feeding and reproductive behaviour, and the capacity to reside year-round in near-polar environments. At the highest palaeolatitudes where dinosaurs have been found (82–85 °N) winter darkness lasted for ~ 120 days and the spring and autumn twilight periods for ~ 15 days. A mostly cloud and mist-shrouded environment witnessed a mean annual temperature (MAT) of 6–7 °C, a warm month mean temperature (WMMT) of 14.5 ± 3.1 °C and a cold month mean temperature (CMMT) of −2 ± 3.9 °C. Growth rings in wood suggest summer temperatures frequently fell below + 10 °C. Winter temperatures as low as −10 °C were likely for short periods. Spring bud break in late February to early March and leaf fall in early October limited the time when fresh food was available in any quantity to not more than 6 months. The diversity of Arctic dinosaur body sizes implies a range of overwintering strategies but year-round residency requires reproduction. Burrowing and enclosed nest building no doubt facilitated overwintering for small animals, but for larger dinosaurs shelter was problematical. No dinosaur egg remains have yet been found as far north as 82° palaeolatitude, but they occur 6° further south in the Early Maastrichtian Kakanaut Formation, Northeastern Russia. Here the winter darkness was shorter (45 days), and the temperature regime warmer (MAT 10 °C, WMMT 19 °C, CMMT + 3 °C). The growing season (temperatures > 10 °C) was ~ 6.3 months and fresh food was available in quantity for slightly longer. These summer temperatures constrain the thermal regime of nest environments and suggest sophisticated nest management and possibly brooding strategies for the necessary rapid incubation and hatching before the onset of winter.

Fossil leaves from the Siwalik sedimentary rocks of Darjeeling sub-Himalaya, evidence a variety of plant–insect interactions that operated during the evolution of monsoon-influenced forests from middle Miocene times. We assessed the diversity and frequency of insect herbivory on 137 specimens representing the Darjeeling lower Siwalik flora (DLSF). We also examined the percent of leaf area removed by herbivory as an independent measure of the effect of insect herbivore removal of host plant photosynthetic tissue. Five functional feeding groups (FFGs) are identified in this study namely leaf mining, hole feeding, skeletonizing, galling and margin feeding. These traces indicate that insects interacted with the plants for various purposes, including feeding, egg laying and sheltering. Furthermore, these morphotraces tend to suggest similarities in insect interactions with leaves of extant plant species such as Persea, Woodfordia, Shorea, Artocarpus, Callicarpa, Albizia, Lagerstroemia etc. On the basis of comparison with extant taxa, possible leaf feeders could have belonged to the insect orders Orthoptera, Coleoptera, Lepidoptera and Diptera. Although the morphology of the phytophagous insects associated with the fossil leaves is unknown, present findings reveal that many modern plant–insect relationships were established by the Miocene time and continue to the present, shaping both the present day flora and fauna. In the present study we compare insect herbivory at DLSF to that of our previously investigated Arunachal lower Siwalik flora and two younger floras from that area. We note a similar range of FFGs and damage types observed among these four fossil floras and conclude that compared to biotic factors climate had little influence in determining the evolution of plant-insect interactions in the eastern Himalayan region.

Ceratophyllaceae Gray is a cosmopolitan submersed family in angiosperm. The fossil record is mainly composed of fruits ranging in age from the Cretaceous to the Neogene within the Northern Hemisphere. However, its fossil record in Asia is sparse. Here we report on a fossil fruit attributed to Ceratophyllum aff. muricatum Cham. from the early middle Eocene of the Niubao Formation in Bangor County, central Tibetan Plateau, China, which is characterized by marginal lateral spines, a style and two basal spines and a small smooth, possibly warty body. This is the earliest fossil record of Ceratophyllaceae in Asia, and it indicates a dispersion from North America to Asia as well as a much wider distribution of Ceratophyllum during the Eocene than previously thought. Moreover, this fossil record demonstrates that the depositional site corresponds to a shallow freshwater environment. The climate was tropical to sub-tropical, consistent with environmental conditions of other fossils findings in the same site. Besides, the climate condition was totally different from the present, largely due to the Neogene formation of central Tibetan Plateau.

Many factors influence leaf anatomy and morphology in the crown of a tree, particularly those resulting from microclimatic differences between the periphery and the interior of the crown. These influences can be so strong that single species can produce different leaf forms in which shade and sun leaves exhibit consistently distinctive morphological and epidermal character sets. Here we show, using Liquidambar as a model system, that the principal morphological characters for distinguishing shade and sun leaves in two modern Liquidambar spp. with different lamina types (entire in L. chinensis and lobate in L. formosana) are the leaf lamina length to width ratio, the degree of development of venation networks, tooth size and tooth shape. The main epidermal characters are ordinary cell size and anticlinal wall outlines. Many fossils, however, are only preserved as impressions and morphological characters alone have been used to distinguish shade and sun leaf morphotypes. To evaluate the utility of our approach, populations of fossil Liquidambar leaves from the Eocene of southern China, preserved only as impressions, were categorized into sun and shade morphotypes. Recognition that sun and shade leaf morphological diversity exists in fossil populations will enable palaeobotanists to identify more reliably foliar polymorphisms that would otherwise be used to describe, incorrectly, different species.

Aim Early in their evolution, angiosperms evolved a diversity of leaf form far greater than that of any other group of land plants. Some of this diversity evolved in response to varying climate. Our aim is to test the global relationship between leaf form in woody dicot angiosperms and the climate in which they live.

Seven fossil leaves with cuticle described here were collected from the lower, middle and upper strata of Siwalik (middle Miocene–lower Pleistocene) sediments of Arunachal Pradesh, India. A detailed comparison of the cuticular analysis of the fossils and their living relatives indicate that these fossil species belong to Dysoxylum raptiensis, Macaranga cf. denticulata, Calophyllum suraikholensis, Combretum prechinense, Actinodaphne palaeoangustifolia, Shorea siwalika and Dipterocarpus koilabasensis. Among these fossil species C. prechinense has been described as a new species. The present day distribution of the modern equivalent taxa of the fossils, structural features and the micro-morphological features of the fossil leaves together with epiphyllous fungal remains collectively indicate the prevalence of a warm humid tropical climate in this area during Siwalik sedimentation. The cuticular micro-morphological features help to confirm the identification of their leaf compressions to the species level and are clearly indicative of mesophytic ecological conditions that reflect a tropical climate with high precipitation. This is the first time Cenozoic fossil leaves of Dysoxylum, Macaranga, Calophyllum, Combretum, Actinodaphne, Shorea and Dipterocarpus are described using the micromorphology of their epidermis.

Early Eocene (~ 55–52 Ma) laminated lacustrine sediments overlying lignites in the Gurha Mine (27.87398°N, 72.86709°E), Rajasthan, India, yield a diversity of fossil leaves, flowers, fruits, seeds and insects. CLAMP (multivariate foliar physiognomic) analysis of two horizons separated by an estimated several tens of thousands of years of deposition indicates cool equatorial (~ 10°N) temperatures and a pronounced monsoon signature. A lower assemblage consisting of 54 leaf morphotypes and an upper assemblage of 57 leaf forms yielded mean annual temperatures (MAT) of 24.7 and 23.9 °C, respectively. The uncertainty (± 2.82 °C) means these temperature regimes are identical despite few similarities in the morphotypes between the two assemblages.The mean annual range of temperature (MART) was approximately 9.7 °C for both assemblages. When corrected for evapotranspirational cooling these temperature regimes are similar to those experienced today at 10°N on the west coast of India and surprisingly cool for the tropics at a time of extreme global warmth. Growth was year round. The tropical to paratropical fossil floras also suggest a moist regime (80% annual relative humidity) and high mean annual precipitation of ~ 1800 mm for both assemblages but with a pronounced wet/dry seasonality indicative of a pronounced monsoonal regime. The lower assemblage has a stronger monsoon index (11.8) than the upper assemblage (8.8). The two assemblages seem to have been deposited less than 100 ka apart. This suggests that not only a pronounced South Asian monsoon existed when India and Asia first made contact, but also a variation in monsoon strength existed that cannot be ascribed to tectonic drivers.

The middle Eocene (Lutetian–Bartonian, 48.6–37.2 Ma) near-equatorial megafossil flora from swamp and lacustrine facies of the lower Changchang Formation, Hainan Island, South China (19.631463°N, 110.445049°E) is highly diverse (> 200 taxa) dominated by an unusual mixture of angiosperms typical of modern temperate, subtropical and tropical evergreen and deciduous forms. It is also rich in palms. Multivariate analysis of the architecture of minimally transported woody dicot leaves reveals a mean annual air temperature (MAT) of ~ 22 ± 4.7 °C with a marked thermal seasonality range of ~ 21 °C. The year-round humid climate lacked any monsoonal signature. The overall climate signal is compatible with the growth characteristics exhibited by fossil wood, but is warmer than the climate signal derived from pollen and spores using Co-existence Analysis. Corrections for possible palaeoelevation of the basin bring the megafossil-derived MAT estimate in line with 54–52 Ma sea surface and soil temperatures obtained from the Gulf Coast, USA, (palaeolatitude ~ 30°N) using multiple geochemical proxies and supports the claim that the low latitude Eocene climate was not uniformly warm. This challenges previous conclusions based on ∂ 18 O analysis of unaltered calcareous microfossils. Our air temperature data also adds to the challenge of understanding heat transport away from the equator to higher latitudes during ‘hothouse’ climate regimes.

The percentage of woody dicots with entire-margined leaves in a flora is known to be positively correlated with mean annual temperature (Leaf Margin Analysis — LMA) but this relationship is not globally uniform. In particular the floras of Australia and New Zealand have been regarded as displaying a different physiognomic relationship to climate than floras seen in the Northern Hemisphere. This difference is more marked in New Zealand where the LMA relationship appears entirely absent. Here we amass data for both Northern and Southern hemispheres using standard protocols and show that regional variations in the leaf margin–mean annual temperature relationship are real but become less significant when other characters are included. Even New Zealand falls into line and most of the mean annual temperature signal in New Zealand floras is encoded in non-margin features. We introduce a new CLAMP (Climate Leaf Analysis Multivariate Program) calibration dataset for the Southern Hemisphere, comprising leaf physiognomic data from Argentina, Bolivia, South Africa, Australia, New Zealand and other Pacific Islands that offers comparable precision for climate prediction to similar datasets derived from the Northern Hemisphere.