Earliest mammals of India

AN INTRODUCTION TO THE MAMMALIAN FAUNA OF THE SIWALIK SYSTEM - Biodiversity of the Siwalik Fauna: K.N. Prasad; Prasad Publications, 8, Venkataraman Street, Srinivasa Avenue, Raja Annamalaipuram, Chennai-600028. Rs. 300.

`SIWALIK' (SEWALIK) Hills, which existed in India, about 20 million years ago, during the Tertiary geological period, south of the Himalayas, between the Indus and the Brahmaputra Rivers, was the cradle of the earliest vertebrates, particularly the mammals of India.

The author of the book under review, a former Director of the Geological Survey of India, who personally participated in the geological explorations of the Siwalik systems, and who has examined the museum collections of the Siwalik fossils, both in India as well as abroad, collaborating with renowned experts and authors, has strived to bring together, the sparse and widely scattered literature into one book, for the benefit of students and researchers in the Siwalik palaeontology, biodiversity and biostratigraphy.

Due to great tectonic movements and climatic changes during the early Tertiary period, early mammals undertook mass migrations, resulting in evolutionary radiations and speciations. Indian sub- continent was then interestingly connected in the north-east with North America, through the Bering land-bridge, so that inter- migrations of early mammals, between the Indian region and North America in the east, and between India and Central Asia and Europe in the west were possible. Faunal migrations into the peninsular India also could have taken place, since some deposits in the Narmada, Godavari and Manjra River valleys and in the Karnul (Kurnool) caves are equated to those of the Upper Siwalik period, containing interesting mammalian as well as anthropoid (ape-like) and even hominid (human-like) fossils.

The chapter on the Siwalik Primates (lemurs, monkeys, apes and humans) in this book is naturally very interesting, particularly because of the discovery of two species of early hominid fossils of Ramapithecus, from the Chinji-Nagri Siwalik beds. They could be the precursors of the Australoid human (Australopithecus) of Africa, through a ``missing link'', which the author believes, might be discovered in the Siwaliks themselves. Africa seems to be the original home of the Probosciden (mammoths and elephants). Six species of the mastodons (Stegodon) were known from the Tertiary formations of India. Despite the several species of early elephants known from India, strangely none of them managed to migrate to Australia. Hipparion, the ancestor of the horse, which occurs in the Chinji beds of the Siwaliks could have come into India from Asia and Europe, rather than from North America. The Siwaliks were the centre of evolutionary radiation for the girrafids, which migrated to North America and Africa, but totally disappeared from India itself. The ancestral home of the rhinoceros is believed to be North America, from where they migrated into India. Other mammalian groups like the Bovoidea (cattle), Rodentia, Carnivora, Suiodea (pigs), hippopotamus, Traguloidea (deer) and Edentata from the Siwalik fossil remains also are described.

Although the subject matter is naturally very technical, dry as the fossil bones, the author has managed to put it as an interesting narration of the palaeo-geography, palaeo-climatology and palaeo-ecology, as determining the palaeo-biodiversity of the remote past, emphasising the focal point that environmental (ecological) interactions of living beings, ultimately determine speciation and biogeography.

P.J. SANJEEVA RAJ

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