Suryendu Dutta

Direct chemical evidence for eumelanin pigment from the Jurassic period

Melanin is a ubiquitous biological pigment found in bacteria, fungi, plants, and animals. It has a diverse range of ecological and biochemical functions, including display, evasion, photoprotection, detoxification, and metal scavenging. To date, evidence of melanin in fossil organisms has relied entirely on indirect morphological and chemical analyses. Here, we apply direct chemical techniques to categorically demonstrate the preservation of eumelanin in two > 160 Ma Jurassic cephalopod ink sacs and to confirm its chemical similarity to the ink of the modern cephalopod, Sepia officinalis. Identification and characterization of degradation-resistant melanin may provide insights into its diverse roles in ancient organisms.

Stratigraphy, sedimentology and bulk organic geochemistry of black shales from the Proterozoic Vindhyan Supergroup (central India)

Four organic-rich shale units of the Proterozoic Vindhyan sedimentary succession have been scanned to reveal their origin and hydrocarbon potential. The wavy-crinkly nature of the carbonaceous laminae is suggestive of a microbial mat origin of the shales. These shales are thus different from Phanerozoic black shales which typically exhibit planar laminae. The hydrocarbon potential of the black shale units has been evaluated by Rock-Eval pyrolysis. Total organic carbon content of many of the shales exceeds 1%. The meanTmax for the black shales translate to a vitrinite reflectance range of 2.05-2.40% Rm based on standard conversion techniques. These shales have reached the catagenetic stage near the beginning of anthracite formation.

A Diverse Paleobiota in Early Eocene Fushun Amber from China

Paleogene arthropod biotas have proved important for tracing the faunal turnover and intercontinental faunal interchange driven by climatic warming and geodynamic events [1-5]. Despite the large number of Paleogene fossil arthropods in Europe and North America [5-8], little is known about the typical Asian (Laurasia-originated) arthropod biota. Here, we report a unique amber biota (50-53 million years ago) from the Lower Eocene of Fushun in northeastern China, which fills a large biogeographic gap in Eurasia. Fushun amber is derived from cupressaceous trees, as determined by gas chromatography-mass spectrometry, infrared spectroscopy, and paleobotanical observations. Twenty-two orders and more than 80 families of arthropods have been reported so far, making it among the most diverse amber biotas. Our results reveal that an apparent radiation of ecological keystone insects, including eusocial, phytophagous, and parasitoid lineages, occurred at least during the Early Eocene Climatic Optimum. Some insect taxa have close phylogenetic affinities to those from coeval European ambers, showing a biotic interchange between the eastern and western margins of the Eurasian landmass during the Early Paleogene.

Membrane Vesicles of Group B Streptococcus Disrupt Feto-Maternal Barrier Leading to Preterm Birth

Infection of the genitourinary tract with Group B Streptococcus (GBS), an opportunistic gram positive pathogen, is associated with premature rupture of amniotic membrane and preterm birth. In this work, we demonstrate that GBS produces membrane vesicles (MVs) in a serotype independent manner. These MVs are loaded with virulence factors including extracellular matrix degrading proteases and pore forming toxins. Mice chorio-decidual membranes challenged with MVs ex vivo resulted in extensive collagen degradation leading to loss of stiffness and mechanical weakening. MVs when instilled vaginally are capable of anterograde transport in mouse reproductive tract. Intra-amniotic injections of GBS MVs in mice led to upregulation of pro-inflammatory cytokines and inflammation mimicking features of chorio-amnionitis; it also led to apoptosis in the chorio-decidual tissue. Instillation of MVs in the amniotic sac also resulted in intrauterine fetal death and preterm delivery. Our findings suggest that GBS MVs can independently orchestrate events at the feto-maternal interface causing chorio-amnionitis and membrane damage leading to preterm birth or fetal death.

Chuaria circularis from the early Mesoproterozoic Suket Shale, Vindhyan Supergroup, India: Insights from light and electron microscopy and pyrolysis-gas chromatography

Chuaria circularis (Walcott 1899) from the Suket Shale of the Vindhyan Supergroup (central India) has been reinvestigated for its morphology and chemical composition using biostatistics, electron microscopy and pyrolysis-gas chromatography. Morphology and microscopic investigations provide little clues on the specific biological affinity ofChuaria as numerous preservational artifacts seem to be incorporated. On the contrary, the predominance of η aliphatic pyrolysates of presently studiedChuaria from India rather supports an algal affinity. Moreover, the reflectance ofC circularis can be used to obtain a comparative maturity parameter of the Precambrian sediments. The review of the age and geographical distribution ofC circularis constrains that this species cannot be considered as an index fossil for the Proterozoic time.

Foraminiferal biostratigraphy of lignite mines of Kutch India: Age of lignite fossil vertebrates

Abstract The lignite deposits of Kutch, India are stratigraphically referred to the Naredi Formation and considered to be Early Eocene in age. The biostratigraphy of the older mine at Panandhro and a newly opened mine at Matanomadh has constrained the upper age limit of lignite to the early Bartonian. Its lower age may extend to the late Lutetian. Temporally the formation of lignite corresponds to the warming event of the Middle Eocene and suggests a humid climate at the onset of the warming. The previous palynological studies have already suggested dominance of tropical angiospermic pollen. A diverse assemblage of fossil whales and other vertebrates, many of them supposedly the oldest representatives, were reported from Panandhro mine. These were initially assigned to the Early Eocene and later to the Lute‑ tian age. The present biostratigraphic study revises their age to the Early Bartonian.

Exceptional preservation of angiosperm markers in Miocene and Eocene ambers

The traditional organic geochemical view suggests that polar triterpenoids are degraded easily during fossilization of organic matter. For the first time, we show that dammarane-type tetracyclic polar triterpenoids are preserved in the geosphere. Hydroxydammarenone (20-hydroxy-24-dammaren-3-one), a typical constituent of extant Dipterocarpaceae (an angiosperm tree family) derived dammar resin, is preserved in Miocene amber. The oxidative products of hydroxydammarenone (i.e., 20,24-epoxy-25-hydroxydammaran-3-one, and hexakisnor-dammaran-3,20-dione) are found in both Miocene and Eocene ambers. The presence of hydroxydammarenone in Miocene amber clearly depicts that natural biotriterpenoid markers can be preserved in the geosphere for tens of millions of years. This result demonstrates that the dammarane-type oxygenated compounds, which are extensively used in archaeological studies, can also be utilized as diagnostic markers for paleochemosystematics.

Palynology, palaeoecology and palaeodepositional environment of Eocene lignites and associated sediments from Matanomadh mine, Kutch Basin, western India

Extensive Cenozoic lignite-bearing sediments in the western part of Kutch, western India provide a unique opportunity to study the floral diversity at a crucial time of early Eocene Climatic Optimum (EECO). Rock samples representing a lignite-bearing sequence from the open cast mine at Matanomadh, Gujarat, western India were collected to study the palynofloral composition and to interpret the palaeoclimate and environment of deposition. The sequence mainly composed of lignites, shales and calcareous mudstones yielded rich assemblage consists of pteridophytic spores (7 genera, 10 species), angiosperm pollens (20 genera, 26 species), fungal remains (14 genera, 16 species) and dinoflagellate cysts. The palynofloral assemblage is marked with dominance of angiospermic pollen, particularly those having affinity with the family Arecaceae. Occurrence of fungal remains in high abundance is also noticed. Based on palynomorph contents, the studied sequence is divisible into two palynozones. It is inferred that lower part of the sequences was deposited in a near-shore environment with intermittent marine incursions whereas the depositional regime of upper part was shallow marine. The climate is found to be tropical-subtropical, humid with heavy precipitation during the deposition of Matanomadh lignite-bearing sequence.

Preserved lignin structures in early eocene Surat lignites, Cambay Basin, Western India

Lignite samples from Vastan and Tadkeshwar lignite mines, Cambay Basin have been analysed to elucidate lignin precursor using thermochemolysis-gas chromatography-mass spectrometry. The thermochemolysis products of lignites are characterized by monomethoxy-, dimethoxy-, and trimethoxybenzene derivatives originated from p-hydroxyphenyl, guaiacyl, and syringyl units of lignin polymer, respectively. The other compounds obtained in thermochemolysates of studied lignites are some resin derived C15 sesquiterpenoids, with a series of fatty acid methyl esters and n-alkanes/alkenes. The methylated guaiacyl and syringyl derivatives originate from the cleavage of β-O-4 linkages and subsequent methylation of acidic hydroxyl groups of preserved lignin. Gymnosperm lignin is characterized mainly by guaiacyl derivatives whereas angiosperm lignin yields some syringyl-type compounds in addition to guaiacyl-type compounds. By analogy with the lignin structure of modern trees, the abundant occurrences of syringyl derivatives in the thermochemolysis products of Surat lignites clearly demonstrate that the palaeofloral community was dominated by angiosperms during the deposition of these lignites.

Black Shale in Late Jurassic Jhuran Formation of Kutch: Possible Indicator of Oceanic Anoxic Event?

This paper reports the results of sedimentary facies analysis and organic geochemical investigations of the middle Member of the Jurassic Jhuran Formation of Kutch which is conspicuous by the occurrence of organic-rich shales. Five lithofacies have been identified for lower part of the Middle Member, e.g. Facies A: Black shale, Facies B: Black shale with siltstone inter-bedding, Facies C: shale and siltstone alternations with minor sandstones, Facies D: siltstone-sandstone alternations and Facies E: plane laminated and hummocky cross-stratified sandstone. The average TOC content of the shales decreases from facies A (av. TOC- 3.4%), to facies D (av. 0.6%) through facies B (av. 1.75%) and facies C (av. 1.34%). The Facies E comprises dominantly of hummocky cross-stratified sandstones. The facies study indicates storm-influenced, shallow marine depositional conditions. Organic geochemical study of shale samples collected from several outcrops from Bhuj to Zara suggests a mixture of type III and type IV kerogen, supplied from higher plant sources. Although most organic matters are mildly matured (av. Tmax c. 427°C), some of the samples reflect overheating related to extrusion of Deccan basalt (av. Tmax c. 604°C). V, Ni, and Co concentrations are indicative of anoxic condition within the depositional settings. The Ni/Co ratio (av. 2.5) and V/(V+Ni) ratio (av. 0.82) as well as size of pyrite framboids (7 to 20 micron), advocates intermittent anoxic and sulfidic conditions in the depositional setting. Black shales within the Jhuran Formation possibly suggest intermittent anoxia related to late Jurassic Oceanic anoxic event (OAE). Detailed investigations are needed to explain the factors causing anoxia in shallow marine conditions.