A novel fossil-species of Meliolinites Selkirk (fossil Meliolaceae) and its life cycle stages associated with an angiosperm fossil leaf from the Siwalik (Mio-Pliocene) of Bhutan sub-Himalaya.

Here, we report the in-situ occurrence of a new fossil-species of Meliolinites (fossil Meliolaceae), Meliolinites bhutanensis sp. nov. on the cuticle fragments of a compressed angiosperm dicot leaf recovered from the middle Siwalik (Formation II: latest Miocene to Pliocene) of Bhutan, eastern Himalaya. This unique foliicolous new fossil fungal species features well-preserved mycelia consisting of superficial, brown to dark brown, septate, thick-walled, branching hyphae with bi-cellular appressoria, unicellular phialides, and a characteristic long, slightly curved hyphal seta. The web-like, brown to dark brown fungal colonies also include globose to sub-globose, dark brown ascomata, and oblong to broadly cylindrical, 5-celled, 4-septate, brown to dark brown, mature ascospores. As almost all features of different stages in the life cycle (ascospores, mature germinating ascospores, superficial lateral hyphae, hyphal seta, hyphopodia, mycelial colony, and ascomata) of this new fossil-species are found, we have proposed the first time a possible life cycle of fossil-species of Meliolaceae. The in-situ evidence of M. bhutanensis on the host leaf cuticle indicates the possible existence of a host-ectoparasite relationship in Bhutan sub-Himalaya's ancient warm and humid tropical evergreen forest during the deposition. So, M. bhutanensis might have thrived generally under warm and humid climate conditions for its growth and development in the Mio-Pliocene time, which is in conformity with our recently published quantitative climatic data by CLAMP (Climate Leaf Analysis Multivariate Program) analysis.

Identification of Chitin in Pliocene Fungi Using Py-GC × GC-TOFMS: Potential Implications for the Study of the Evolution of the Fungal Clade in Deep Time.

Molecular dating estimates the origin of the fungal clade to the Pre-Cambrian. Yet, the oldest unambiguous fungal fossils date to the Ordovician and show remarkable diversity and organizational development. Recent studies have suggested that the dates for the emergence of fungi in the fossil record may be pushed back to the Proterozoic. However, the nonspecificity of the methods used in those studies necessitates the employment of a wider variety of analytical techniques that can independently verify the presence of chitin, a crucial prerequisite in the assignment of fungal affinity, particularly of putative fossils from the Pre-Cambrian. In this paper, we propose Py-GC × GC-TOFMS as an example of one such technique. We analyze fungal fossils from the Pliocene. We find that a suite of N-bearing compounds are present in the pyrolysis products of these fossils, from which we suggest that 3-acetamidopyrones and their methylated homologues can serve as specific pyrolytic markers for chitin. We discuss both how this technique can potentially be used to differentiate between biopolymers, including those similar to chitin such as peptidoglycan, and the potential implications of identifying such markers in fossils from deep time. We conclude that Py-GC × GC-TOFMS is a promising technique that can potentially be used alongside, or independent of, staining methods to detect the presence of chitin in fossils.

A comprehensive calibrated phytolith based climatic index from the Himalaya and its application in palaeotemperature reconstruction.

Past climate reconstructions from palaeoecological records require an understanding of relationships between modern vegetation and climate. Phytoliths are being used widely to reconstruct variations in C3/C4 grasses in the past vegetation and corresponding climate. However, little understanding is available on their relationships with the climate driver(s). Even though, the driver(s) regulating C3/C4 grass distributions vary regionally, while reconstructing the past distributions, a grass phytolith-based climatic index (Ic) has often been found to be used globally without assessing its regional consistency. In the Himalaya, the working potential of Ic has proven to be unsatisfactory when compared to other regions of the globe. To improve the efficacy of Ic, we have identified the redundant grass phytolith morphs and revised it by including four exclusive C3-grass indicator morphotypes (bilobate trapezoidal, bilobate scooped, saddle tall and saddle plateaued) to the existing Ic calculation. Thus, a new climatic index, revised Ic (rIc) is proposed in this article. We have compared the rIc with modern climate variables and a relationship with mean annual temperature (MAT) is established with statistical validation. To assess the working potential of the proposed calibration function in the past temperature reconstructions, we have estimated the late Holocene MAT variations in the Himalaya using rIc. We infer that in the mountainous regions like the Himalaya, even with irregular precipitation distribution, variability in C3/C4 grass distributions and their phytolith spectra seem to be a primary function of temperature. Further, we recommend that rIc can be satisfactorily used to reconstruct past temperature variations in the Himalaya and similar mountainous regions where soil water availability is not a limiting factor.

Evidence of fungal decay in petrified legume wood from the Neogene of the Bengal Basin, India.

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.

Occurrence of Phoma Sacc. in the phyllosphere of Neogene Siwalik forest of Arunachal sub-Himalaya and its palaeoecological implications.

The present study reports in situ occurrence of two new epiphyllous fungal species of Phomites (comparable to modern genus Phoma Sacc.) on angiospermic leaf remains recovered from the Siwalik sediments (middle Miocene to early Pleistocene) of Arunachal Pradesh, eastern Himalaya. We describe two new species i.e. Phomites siwalicus Vishnu, Khan et Bera S, sp. nov. and Phomites neogenicus Vishnu, Khan et Bera S, sp. nov. on the basis of structural details of pycnidia. The pycnidium is a globose or slightly lens-shaped, ostiolate with a collar layer consisting of thick walled cells, sunken in leaf cuticle, with one-celled conidiospores and short-ampulliform conidiogenous cells. Host leaves resemble to those of extant Dipterocarpus C. F. Gaertn., Shorea Roxb. ex C. F. Gaertn. (Dipterocarpaceae), Dysoxylum Blume (Meliaceae), and Poaceae Barnhart. In situ occurrence of two Phomites morphotypes on the said leaf remains suggests a possible host-parasite interaction in the moist evergreen forest of Arunachal sub-Himalaya during Mio-Pleistocene period. The occurrence of Phomites in appreciable numbers indicates a humid climate favored by high rate of precipitation during Siwalik sedimentation, which is also consistent with our previously published climatic data obtained from the study of the macroscopic plant remains.