41 research outputs found
Occurrence of <i>Shorea</i> Roxburgh ex C. F. Gaertner (Dipterocarpaceae) in the Neogene Siwalik forests of eastern Himalaya and its biogeography during the Cenozoic of Southeast Asia
We report the occurrence of two leaf impressions and one leaf compression along with one winged fruit and two fruiting calyx lobes, resembling those of Shorea Roxburgh ex C. F. Gaertner, in the lower Siwalik (Dafla Formation, middle to upper Miocene), middle Siwalik (Subansiri Formation, Pliocene) and upper Siwalik (Kimin Formation, upper Pliocene to lower Pleistocene) sediments exposed in Arunachal Pradesh, eastern Himalaya. We determine their taxonomic positions based on morphological comparison with similar extant and fossil specimens and discuss their phytogeographic and paleoclimatic implications in terms of the distribution and habitat of fossil and modern populations. The Miocene winged fruit is recognized as Shorea pinjoliensis Khan, R.A. Spicer et Bera, sp. nov. while the Pliocene and Plio-Pleistocene fruiting calyx lobes are recognized as Shorea bhalukpongensis Khan, R.A. Spicer et Bera, sp. nov. and Shorea chandernagarensis Khan, R.A. Spicer et Bera, sp. nov. respectively. Based on leaf architecture the Miocene, Pliocene and Plio-Pleistocene leaves are recognized as Shorea mioobtusa Khan, R.A. Spicer et Bera, sp. nov., Shorea pliotumbuggaia Khan, R.A. Spicer et Bera, sp. nov. and Shorea nepalensis Konomatsu et Awasthi respectively. The discovery of members of Shorea indicates that they had arrived in a tropical, warm and humid eastern Himalaya by the Mio-Pleistocene. Present and earlier records of Shorea suggest that this genus was a common forest element during Neogene (Miocene time) as well as in the Siwalik forests including Arunachal sub-Himalaya. In this paper, we also review in detail the biogeographic history and suggest possible migration routes of the genus
First occurrence of mastixioid (Cornaceae) fossil in India and its biogeographic implications
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
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Earliest megafossils of scandent calamoid palms from the Deccan Intertrappean Beds of Central India and their paleobiogeographic implications
Two well-preserved petrified palm stems from the latest Maastrichtian (Late Cretaceous) to earliest Danian (Early Paleocene) sediments of the Deccan Intertrappean Beds of Madhya Pradesh, Central India are described. Their significant anatomical characteristics include a Calamus-type general stem pattern, the presence of well-preserved fibrovascular bundles (fvbs) with two wide metaxylem vessel elements (230 μm–250 μm) and one phloem strand, uniform density of fvbs, lack of continuity between protoxylem and metaxylem vessel elements, and an absence of centrifugal differentiation of sclerenchymatous fibrous parts. These features reveal a close resemblance to those of extant genera of scandent Calamoideae. The permineralized stems are described as a new species namely, Palmoxylon calamoides Kumar, Roy et Khan sp. nov. The fossils represent the oldest reliable fossil records of this family, supporting their Gondwanan origin, their importance in tracing their migration pathways from India to Europe and other continents after the docking of the Indian subcontinent with Eurasia during the Paleocene, and an “Out-of-India” dispersal hypothesis. Today the subfamily Calamoideae is disjunctly occurred in Africa, Asia, Australia, Europe, and South America, but the poor deep-time fossil record of this subfamily with a small number of Cenozoic fossils makes hypotheses concerning its origin and dispersal difficult to evaluate. The present study has significant implications for the origin and migration of this subfamily and the paleoclimate
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Siwalik plant megafossil diversity in the Eastern Himalayas: A review
The Eastern Himalayas are renowned for their high plant diversity. To understand how this modern botanical richness formed, it is critical to investigate past plant biodiversity preserved as fossils throughout the eastern Himalayan Siwalik succession (middle Miocene−early Pleistocene). Here, we present a summary of plant diversity records that document Neogene floristic and climate changes. We do this by compiling published records of megafossil plant remains, because these offer better spatial and temporal resolution than do palynological records. Analyses of the Siwalik floral assemblages based on the distribution of the nearest living relative taxa suggest that a tropical wet evergreen forest was growing in a warm humid monsoonal climate at the deposition time. This qualitative interpretation is also corroborated by published CLAMP (Climate Leaf Analysis Multivariate Program) analyses. Here, we also reconstruct the climate by applying a new common proxy WorldClim2 calibration. This allows the detection of subtle climate differences between floral assemblages free of artefacts introduced by using different methodologies and climate calibrations. An analysis of the Siwalik floras indicates that there was a gradual change in floral composition. The lower Siwalik assemblages provide evidence of a predominance of evergreen elements. An increase in deciduous elements in the floral composition is noticed towards the close of the middle Siwalik and the beginning of the upper Siwalik formation. This change reflects a climatic difference between Miocene and Plio-Pleistocene times. This review helps us to understand under what paleoenvironmental conditions plant diversity occurred and evolved in the eastern Himalayas throughout the Cenozoic
Elective cancer surgery in COVID-19-free surgical pathways during the SARS-CoV-2 pandemic: An international, multicenter, comparative cohort study
PURPOSE As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19–free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19–free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19–free surgical pathways. Patients who underwent surgery within COVID-19–free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19–free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score–matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19–free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION Within available resources, dedicated COVID-19–free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks
Elective Cancer Surgery in COVID-19-Free Surgical Pathways During the SARS-CoV-2 Pandemic: An International, Multicenter, Comparative Cohort Study.
PURPOSE: As cancer surgery restarts after the first COVID-19 wave, health care providers urgently require data to determine where elective surgery is best performed. This study aimed to determine whether COVID-19-free surgical pathways were associated with lower postoperative pulmonary complication rates compared with hospitals with no defined pathway. PATIENTS AND METHODS: This international, multicenter cohort study included patients who underwent elective surgery for 10 solid cancer types without preoperative suspicion of SARS-CoV-2. Participating hospitals included patients from local emergence of SARS-CoV-2 until April 19, 2020. At the time of surgery, hospitals were defined as having a COVID-19-free surgical pathway (complete segregation of the operating theater, critical care, and inpatient ward areas) or no defined pathway (incomplete or no segregation, areas shared with patients with COVID-19). The primary outcome was 30-day postoperative pulmonary complications (pneumonia, acute respiratory distress syndrome, unexpected ventilation). RESULTS: Of 9,171 patients from 447 hospitals in 55 countries, 2,481 were operated on in COVID-19-free surgical pathways. Patients who underwent surgery within COVID-19-free surgical pathways were younger with fewer comorbidities than those in hospitals with no defined pathway but with similar proportions of major surgery. After adjustment, pulmonary complication rates were lower with COVID-19-free surgical pathways (2.2% v 4.9%; adjusted odds ratio [aOR], 0.62; 95% CI, 0.44 to 0.86). This was consistent in sensitivity analyses for low-risk patients (American Society of Anesthesiologists grade 1/2), propensity score-matched models, and patients with negative SARS-CoV-2 preoperative tests. The postoperative SARS-CoV-2 infection rate was also lower in COVID-19-free surgical pathways (2.1% v 3.6%; aOR, 0.53; 95% CI, 0.36 to 0.76). CONCLUSION: Within available resources, dedicated COVID-19-free surgical pathways should be established to provide safe elective cancer surgery during current and before future SARS-CoV-2 outbreaks
The first evidence of saprophytic Tetraploa on Siwalik (Late Miocene) monocot leaf from western Himalaya and its role in palaeoecology reconstruction
Even though the records of Tetraploa spores from Mesozoic and Cenozoic sedimentary strata along with spore-pollen assemblages are numerous and well documented, no foliicolus Tetraploa macroconidia have been reported to date. Here, we report the first occurrence of conidia assignable to modern Tetraploa Berk. & Broome (Tetraplosphaeriaceae: Pleosporales: Dothideomycetes) on cuticular fragments of compressed monocot leaf recovered from the middle Siwalik sediments (Late Miocene; 12–8 Ma) of Himachal Himalaya, India. We determine their taxonomic position based on detailed macromorphological comparison with similar modern and fossil taxa and discuss their palaeoecological significance in terms of the present‐day ecological conditions of modern analogues. This finding also represents an essential data source for understanding Tetraploa’s evolution and diversification in deep time.Fil: Kundu, Sampa. Sidho-kanho-birsha University; IndiaFil: Bianchinotti, Maria Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; ArgentinaFil: Khan, Mahasin Ali. Sidho-kanho- Birsha University; Indi
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Palaeoclimatic estimates for a latest Miocene-Pliocene flora from the Siwalik Group of Bhutan: Evidence for the development of the South Asian Monsoon in the eastern Himalaya
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
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Floral diversity and environment during the middle Siwalik sedimentation (Pliocene) in the Arunachal sub-Himalaya
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