Mahasin Ali Khan

On some fabaceous fruits from the Siwalik sediments (Middle Miocene-Lower Pleistocene) of Eastern Himalaya

Four legume fruits (Fabaceae) from the Siwalik sediments (middle Miocene to lower Pleistocene) of Darjeeling and Arunachal Pradesh of Eastern Himalaya are described here. One fossil fruit, Dalbergia prelatifolia sp. nov., is recovered from the lower part of the Siwalik succession (Gish Clay Formation of Sevok Group; middle to upper Miocene) of Darjeeling foothills. Mastertia neoassamica sp. nov. and Acacia miocatechuoides sp. nov. are collected from the lower part of the Siwalik succession (Dafla Formation; middle Miocene to upper Miocene), while Pongamiakathgodamensis Prasad is recovered from the upper part of the Siwalik succession (Kimin Formation; upper Pliocenelower Pleistocene) of Arunachal sub Himalaya. Their presence indicates a warm and humid tropical environment in the region during the Siwalik sedimentation.

Evidence for diversification of Calophyllum L. (Calophyllaceae) in the Neogene Siwalik forests of eastern Himalaya

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.

First megafossil evidence of Cyatheaceous tree fern from the Indian Cenozoic

A part of the compressed tree fern axis with leaf and adventitious root scars in unusual arrangement from Plio–Pleistocene sediments of Arunachal Pradesh, India is described as Cyathea siwalika sp. nov. This record suggests that Cyathea was an important component of tropical evergreen forest in the area during the Plio–Pleistocene and this group subsequently declined in importance within the local vegetation.

First fossil evidence of Connaraceae R. Br. from Indian Cenozoic and its phytogeographical significance

Fossil leaflet impression described here as a new species Rourea miocaudata sp. nov., showing close resemblance with the modern leaflets of Rourea caudata Planch. (Connaraceae R. Br.), has been recorded from the lower part of the Siwalik sediments (Dafla Formation, middle–upper Miocene) exposed at the road-cutting section of Pinjoli area in West Kameng district, Arunachal Pradesh. The important morphological characters of the fossil are its narrow elliptic leaflet, cuneate base, long caudate apex, entire margin, eucamptodromous to brochidodromous secondary veins, presence of intersecondary veins, percurrent and reticulate tertiary veins and orthogonally reticulate quaternary veins. This is the first authentic record of the occurrence of leaflet comparable to R. caudata of Connaraceae from the Cenozoic sediments of India and abroad. At present R. caudata does not grow in India and is restricted only in southeast Asia especially in China and Myanmar. This taxon probably migrated to these southeast Asian regions after lower Siwalik sedimentation (middle–upper Miocene) due to climatic change caused by post-Miocene orogenic movement of the Himalaya. The recovery of this species and other earlier-described evergreen taxa from the same formation, suggests the existence of a tropical, warm and humid climatic conditions during the depositional period.

Occurrence of Persea Mill. from the Siwalik forest of Darjeeling, eastern Himalaya: Paleoclimatic and paleogeographic implications

Fossil leaf remains of two new species of Persea Mill., belonging to the family Lauraceae collected from the lower part of the Siwalik sediments (Gish Clay Formation of Sevok Group, Middle Miocene) of Darjeeling foothills of eastern Himalaya, are described. The new species are Persea miogamblei sp. nov. and Persea neovillosa sp. nov.. On the basis of leaf architecture (size, shape and venation pattern) fossil leaves described in this article closely resemble modern leaves of Persea gamblei (King ex Hook. f.) Kosterm. and Persea villosa (Roxb.) Kosterm.. The geographic distribution of the fossils and their modern counterparts are discussed and on that basis tropical evergreen vegetation with a warm and humid climate at the time of deposition of the Siwalik sediments is suggested in contrast to the present day tropical deciduous vegetation in this area. The present finding also suggests probable migration of these lauraceous taxa to Southeast Asia.

AMBER EMBALMS ESSENTIAL OILS: A RARE PRESERVATION OF MONOTERPENOIDS IN FOSSIL RESINS FROM EASTERN HIMALAYA

Abstract Terpenoids are hydrocarbons, comprising isoprene as their fundamental building blocks, many of which serve defensive functions in plants and protect them from potential enemies in the environment. Preservation of volatile terpenoids in amber is unusual and rarely detected in fossilized remains. In the present study, a remarkable preservation of monoterpenoid constituents are detected in Pliocene–Pleistocene ambers collected from the Siwalik strata of eastern Himalaya. Amongst the monoterpenoids, eucalyptol, borneol, α-pinene and p-cymene are detected in significant abundance. The sesquiterpenoid fraction comprises both biomolecules and geomolecules. Biological compounds include copaene, selinene, OH-bearing compounds such as spathulenol, globulol and α-cadinol as well as isomers of elemene and muurolene. Calamenene and dihydro-ar-curcumene are the diagenetically altered sesquiterpenoids recorded in the samples. High abundances of biotriterpenoids like β-amyrin and α-amyrin as well as moderate concentrations of altered products such as double-bonded ketones and alcohols generated from the parent triterpenoids are detected in the ambers. The results demonstrate that the monoterpenoids, which are particularly susceptible to degradation, could survive exhaustive diagenesis and alteration over a long span of time on rare occasions. The biosynthetic pathways of the secondary metabolite terpenoids, particularly the monoterpenoids, evolved in plants long back in time and are present in the angiosperm clades that evolved much later in Earth history. This indicates the unique efficiency of these volatile terpenoid compounds as defense tools in more evolved and complex biota.