Notes on elements of the Oligocene flora from the Makum Coalfield, Assam, India

Abstract

A new species Daphnogene makumensis sp. nov. (Lauraceae), plus Equisetum sp. both new to the flora, and Mesua antiqua Awasthi et al. are described from the Tikak Parbat Formation of the Makum Coalfield, Assam, India. The formation is considered Late Oligocene in age. The fossil assemblage indicates the existence of tropical evergreen to moist deciduous forest in the region during the Late Oligocene.

Late Oligocene climate and floristic diversity of Assam, Northeast India

“…Remarks-Fossil fruit with similar appearance has been described by Mehrotra et al (2009) from the Makum Coalfield, but it was different in size, shape and length of the beak from the present fossil. Due to lack of many peculiar features, it is difficult to compare the fossil with the modern analogue.…”

“…present fossil can be differentiated from the fossil described by Mehrotra et al (2009) in having elliptic shape and size.…”

“…Remarks-In the absence of many peculiar details it is difficult to compare it with modern taxa. The absence of prominent striations and size difference make it apart from the fossil described by Mehrotra et al (2009).…”

“…After the collision of the Indian Plate with the Eurasian Plate, northeast India acted as a corridor for the migration of biota from India to Southeast Asia and vice-versa (Srivastava & Mehrotra, 2010b;Chatterjee et al, 2013). The Makum Coalfield (27°15'-27°25'N; 95°40'-95°55'E) which is located in Assam, archived an extremely rich floristic diversity and a wide variety of vegetation types, however, evergreen forests dominated a larger part of the vegetation (Awasthi et al,1992;Awasthi & Mehrotra, 1995;Mehrotra et al, 2009;Srivastava & Mehrotra, 2010a, 2013aSrivastava et al, 2012a). Infact, there is no other Oligocene sedimentary basin in India containing such a rich and diversified assemblage of plants.…”

Barringtonia Forster & Forster (Lecythidaceae) leaf from the late Oligocene of Assam, India

“…A large number of plant families have been reported from the Makum Coalfield (Awasthi & Mehrotra, 1995;Mehrotra et al, 2003Mehrotra et al, , 2009Srivastava & Mehrotra 2010, 2012Srivastava et al, 2012a) and among them Annonaceae, Burseraceae, Clusiaceae, Combretaceae, Lecythidaceae, Myristicaceae and Rhizophoraceae are typical pantropical megathermal in nature (van Steenis, 1962) suggesting a tropical climate. Similarly, Fabaceae is the most dominant family whose abundance and richness covary with the temperature (Punyasena et al, 2008) indicating a warm climate.…”