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The colonization and expansion of plants on land is considered one of the most profound ecological revolutions, yet the precise timing remains controversial. Because land vegetation can enhance weathering intensity and affect terrigenous input to the ocean, changes in terrestrial plant biomass with distinct negative Δ 199 Hg and Δ 200 Hg signatures may overwrite the positive Hg isotope signatures commonly found in marine sediments. By investigating secular Hg isotopic variations in the Paleozoic marine sediments from South China and peripheral paleocontinents, we highlight distinct negative excursions in both Δ 199 Hg and Δ 200 Hg at Stage level starting in the early Silurian and again in the Carboniferous. These geochemical signatures were driven by increased terrestrial contribution of Hg due to the rapid expansion of vascular plants. These excursions broadly coincide with rising atmospheric oxygen concentrations and global cooling. Therefore, vascular plants were widely distributed on land during the Ordovician-Silurian transition (~444 million years), long before the earliest reported vascular plant fossil, Cooksonia (~430 million years).

The complex tectonic evolution in the Tibetan region has impacted climate, the Asian monsoon system, and the development of major biodiversity hotspots, especially since the onset of the India-Eurasia continental collision during the early Paleogene. Untangling the links between the geologic, climatic, and ecological history of the broader region can provide insights into these Earth system mechanisms, relevant for the future of our rapidly changing planet. To better understand environmental conditions across this critical time and place, we reconstruct the climatic and environmental history from a key sedimentary repository within the Lühe Basin, Yunnan, China, uniquely located between high elevation Tibet and low elevation coastal China. We investigate a 340-m long section using a multi-proxy organic geochemistry approach, complemented with sedimentological interpretations and climate model simulations. The complementary organic geochemical proxies, including n-alkanes, terpenoids, and hopanes, suggest that these thermally immature sediments were deposited in a dynamic environment that fluctuated between low energy floodplains and high energy fluvial systems. Our branched glycerol diakyl glycerol tetraether-based proxies indicate terrestrial temperatures of around 17 °C ± 3 SD and our model-based temperatures indicate terrestrial temperatures for Chattian of around 19 °C, consistent with the literature palaeobotany-based temperatures from the nearby Lühe town section. These combined palaeotemperatures match present-day values, suggesting that this area has not undergone significant temperature change since the late Paleogene.

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.

Land surface elevation, climate and vegetation are intrinsically linked at a range of spatial and temporal scales. In the case of Asia, complex relief hosts some of the richest biodiversity on our planet and is dominated by a system of monsoons, the features of which are determined in large part by topography and land surface characteristics, including vegetation. Such regions have not only acted as an incubator for evolving species but also as refugia during periods of environmental crisis. The exceptional topography of Asia includes the largest and highest elevated region on Earth, the Tibetan Plateau, along with the Himalaya and the Hengduan mountains, collectively referred to here as the THH region. In recent years there has been a revolution in thinking as to how the THH was formed, how the several monsoons systems that affect it have changed, and how it has influenced regional, even global, biodiversity evolution. Accurately dated plant fossils have played key roles in these advances. Here we review the complex evolution of the THH landscape, the modernization of the biota in the Paleogene, and the transition to the modern landscape and monsoon systems in the Neogene. We show how these changes in understanding have been brought about by recent fossil discoveries and new radiometric dating of previously known assemblages, methodological advances arising from integrating improved proxy data, and numerical palaeoclimate modelling. Significant knowledge gaps remain, however, which demand further advances in proxy and numerical methodologies, as well as new fossil discoveries in key locations for specific time intervals.

BACKGROUND AND OBJECTIVES Annual preparticipation physical evaluation (PPE) is used in the United States to screen adolescents for potential causes of sudden cardiac death. The American Heart Association recommends 14 screening elements of history and physical examination. This study sought to define the utilization of these screening elements by each of the 50 states before high school athletics. METHODS PPE forms were obtained from the public website of the high school athletics governing body in every state. Form content was analyzed to identify which of the 14 screening elements were explicitly fulfilled. Additional PPE forms provided by private/parochial schools, other professional societies, or independent groups were excluded from this study. RESULTS A total of 48 states (96%) had PPE forms posted online. The remaining 2 states (4%) deferred the specific method of PPE documentation to individual school districts and provided no standardized form. Of the 48 states providing PPE forms, 13 (27%) included all 14 American Heart Association screening elements. The median criteria included by each state was 11 (range 3–14). The 3 criteria most commonly absent were (1) the examination of femoral pulses to exclude coarctation (58%), (2) a family history of specific inherited cardiac disease (31%), and (3) personal history of hypertension (27%). CONCLUSIONS Annual preparticipation forms are important screening tools. Only a minority of states include all 14 cardiac screening elements recommended by the American Heart Association.

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 uplift of eastern Tibet, Asian monsoon development and the evolution of globally significant Asian biodiversity are all linked, but in obscure ways. Sedimentology, geochronology, clumped isotope thermometry, and fossil leaf-derived numerical climate data from the Relu Basin, eastern Tibet, show at ∼50-45 Ma the basin was a hot (mean annual air temperature, MAAT, ∼27 °C) dry desert at a low-elevation of 0.6 ± 0.6 km. Rapid basin rise to 2.0 ± 0.9 km at 45-42 Ma and to 2.9 ± 0.9 km at 42-40 Ma, with MAATs of ∼20 and ∼16 °C, respectively, accompanied seasonally varying increased annual precipitation to 1500 mm. From ∼39 to 34 Ma, the basin attained 3.5 ± 1.0 km, near its present-day elevation (∼3.7 km), and MAAT cooled to ∼6 °C. Numerically-modelled Asian monsoon strength increased significantly when this Eocene uplift of eastern Tibet was incorporated. The simulation/proxy congruence points to a distinctive Eocene Asian monsoon, quite unlike that seen today, in that it featured bimodal precipitation and a winter-wet regime, and this enhanced biodiversity modernisation across eastern Asia. The Paleogene biodiversity of Asia evolved under a continually modifying monsoon influence, with the modern Asian monsoon system being unique to the present and a product of a long gradual development in the context of an ever-changing Earth system.

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.

Williams syndrome (WS) is an arteriopathic derangement associated with supravalvular aortic stenosis and branch pulmonary stenosis. We describe double-outlet right ventricle with mitral atresia and aortic arch hypoplasia in an infant with WS. This case demonstrates the difficulty in managing patients with WS with complex cardiac defects. To our knowledge, this is the first reported single-ventricle physiology in a patient with WS. (Level of Difficulty: Advanced.), Graphical abstract, Williams syndrome (WS) is an arteriopathic derangement associated with supravalvular aortic stenosis and branch pulmonary stenosis. We describe…

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.

Origins of an alpine flora The evolution of high mountain floras is strongly influenced by tectonic and climatic history. Ding et al. document the timing, tempo, and mode by which the world's most species-rich alpine flora, that of the Tibet-Himalaya-Hengduan region, was assembled. Alpine assemblages in the region are older than previously thought, with lineages tracing their alpine ancestry to the early Oligocene—older than any other modern alpine system. Alpine species diversified faster during periods of orogeny and intensification of the Asian monsoon, and the Hengduan Mountains—the most species-rich area in this region—played a key biogeographic role as the location of the earliest pulse of alpine diversification in the Oligocene. Science , this issue p. 578

The biodiversity of the Himalaya, Hengduan Mountains and Tibet, here collectively termed the Tibetan Region, is exceptional in a global context. To contextualize and understand the origins of this biotic richness, and its conservation value, we examine recent fossil finds and review progress in understanding the orogeny of the Tibetan Region. We examine the deep-time origins of monsoons affecting Asia, climate variation over different timescales, and the establishment of environmental niche heterogeneity linked to topographic development. The origins of the modern biodiversity were established in the Eocene, concurrent with the formation of pronounced topographic relief across the Tibetan Region. High (>4 km) mountains to the north and south of what is now the Tibetan Plateau bounded a Paleogene central lowland (

Premise of research. Understanding the relationship between field-measured operating stomatal conductance (gop) and theoretical maximum stomatal conductance (gmax), calculated from stomatal density and geometry, provides an important framework that can be used to infer leaf-level gas exchange of historical, herbarium, and fossil plants. To date, however, investigation of the nature of the relationship between gop and theoretical gmax remains limited to a small number of experiments on relatively few taxa and is virtually undefined for plants in natural ecosystems.\ud \ud Methodology. We used the gop measurements of 74 species and 35 families across four biomes from a published contemporary data set of field-measured leaf-level stomatal conductance in woody angiosperms and calculated the theoretical gmax from the same leaves to investigate the relationship between gop and gmax across multiple species and biomes and determine whether such relationships are widely conserved.\ud \ud Pivotal results. We observed significant relationships between gop and gmax, with consistency in the gop ∶ gmax ratio across biomes, growth habits (shrubs and trees), and habitats (open canopy and understory subcanopy). An overall mean gop ∶ gmax ratio of 0.26 ± 0.11 (mean ± SD) was observed. The consistently observed gop ∶ gmax ratio in this study strongly agrees with previous hypotheses that an ideal gop ∶ gmax ratio exists.\ud \ud Conclusions. These results build substantially on previous studies by presenting a new reference for a consistent gop ∶ gmax ratio across many levels and offer great potential to enhance paleoclimate proxies and vegetation-climate models alike.

Mountain ecosystems support a significant one‐third of all terrestrial biodiversity, but our understanding of the spatiotemporal maintenance of this high biodiversity remains poor, or at best controversial. The Himalaya hosts a complex mountain ecosystem with high topographic and climatic heterogeneity and harbors one of the world's richest floras. The high species endemism, together with increasing anthropogenic threats, has qualified the Himalaya as one of the most significant global biodiversity hotspots. The topographic and climatic complexity of the Himalaya makes it an ideal natural laboratory for studying the mechanisms of floral exchange, diversification, and spatiotemporal distributions. Here, we review literature pertaining to the Himalaya in order to generate a concise synthesis of the origin, distribution, and climate change responses of the Himalayan flora. We found that the Himalaya supports a rich biodiversity and that the Hengduan Mountains supplied the majority of the Himalayan floral elements, which subsequently diversified from the late Miocene onward, to create today's relatively high endemicity in the Himalaya. Further, we uncover links between this Miocene diversification and the joint effect of geological and climatic upheavals in the Himalaya. There is marked variance regarding species dispersal, elevational gradients, and impact of climate change among plant species in the Himalaya, and our review highlights some of the general trends and recent advances on these aspects. Finally, we provide some recommendations for conservation planning and future research. Our work could be useful in guiding future research in this important ecosystem and will also provide new insights into the maintenance mechanisms underpinning other mountain systems., Although the Himalaya harbors one of the world's richest floras, our understanding of the origin and spatiotemporal maintenance of this high biodiversity remains poor. This review provides a concise synthesis of the origin, distribution, and climate change responses of the Himalayan flora. Additionally, we suggest some conservation interventions that would be useful for ecosystem management and future research.

Background: Flowering plants (angiosperms) dominate most global ecosystems today, but their rapid Cretaceous diversification has remained poorly understood ever since Darwin referred to it as an ‘abominable mystery’. Although numerous Cretaceous fossil flowers have been discovered in recent years, most are represented by incomplete charcoalified fragments that do not preserve delicate structures such as complete petals and surface textures, which means that their similarity to living forms is often difficult to discern. The scarcity of information about the ecology of early angiosperms makes it difficult to test hypotheses about the drivers of their diversification. Among other factors, frequent fires in the Cretaceous have been postulated as having possibly facilitated the rise of angiosperms. However, to date no early fossil angiosperms displaying fire-adapted traits have been known, making the role of fire in shaping Cretaceous floras uncertain.Results: We report the discovery of two exquisitely preserved fossil flower species, one identical to the inflorescences of the extant crown eudicot genus Phylica and the other recovered as a sister group to Phylica, both preserved as inclusions in Cretaceous amber from northern Myanmar (~99 Ma). These specialized flower structures, named Phylica piloburmensis sp. nov. and Eophylica priscastellata gen. et sp. nov., were adapted to surviving frequent wildfires, providing the earliest evidence of fire-resistance in angiosperms. The fossils suggest that fire was a significant selective force in Cretaceous angiosperm floras and that adaptations to fire resistance in some eudicot clades have been conserved for at least 99 Ma. This morphological stasis encompasses a range of floral characters, including the production of ‘pseudo-flowers’, and characteristic fruit and pollen architecture. Given its morphological distinctiveness, the Eophylica-Phylica clade represents one of the first well-documented angiosperm ‘living fossil’ genera from the Cretaceous. Conclusion: Our study suggests that core eudicots with specialised flower morphology displaying hallmarks of fire resistance and identical to those of the extant south African genus Phylica, had originated by the mid-Cretaceous (~99 Ma). Palaeoenvironmental reconstructions indicate that these plants lived in conditions similar to those of present-day southern Africa where 70% of taxa survive frequent burning, and that fire resistance was probably widespread in the fire-prone Cretaceous. The results also provide new insights into the biogeographic origin of at least one element of the highly endemic Greater Cape Region biodiversity hotspot flora biota.

The rapid Cretaceous diversification of flowering plants remains Darwin's 'abominable mystery' despite numerous fossil flowers discovered in recent years. Wildfires were frequent in the Cretaceous and many such early flower fossils are represented by charcoalified fragments, lacking complete delicate structures and surface textures, making their similarity to living forms difficult to discern. Furthermore, scarcity of information about the ecology of early angiosperms makes it difficult to test hypotheses about the drivers of their diversification, including the role of fire in shaping flowering plant evolution. We report the discovery of two exquisitely preserved fossil flower species, one identical to the inflorescences of the extant crown-eudicot genus Phylica and the other recovered as a sister group to Phylica, both preserved as inclusions together with burned plant remains in Cretaceous amber from northern Myanmar (~99 million years ago). These specialized flower species, named Phylica piloburmensis sp. nov. and Eophylica priscastellata gen. et sp. nov., exhibit traits identical to those of modern taxa in fire-prone ecosystems such as the fynbos of South Africa, and provide evidence of fire adaptation in angiosperms.

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.

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.