Mesozoic era itself was sub divided into Triassic, Jurassic and Cretaceous periods. Triassic period that was between 206 and 250 million years ago saw first dinosaurs evolve. Jurassic extended from 144 to 204 million years and dinosaurs proliferated. It was during this time that birds too came into being. During Cretaceous, flowering plants appeared and dinosaurs became extinct.

It was the Mesozoic era when dinosaurs ruled our planet Earth. Sauropods were the large herbivores and Theropods were the carnivorous kind. Their fossils have been known to exist since 1818 but the term ‘dinosaur’ (deinos means terrifying and sauros means lizard) as such was coined by Sir Richard Owen in 1842. The actual dino hunt in true sense of terms began globally in the 19^th century. Dinosaur remains have been found from China, Patagonia, USA, Mongolia, Europe and most importantly, India.

In India, a skeleton led to the identification of a dinosaur, later named Titanosaurus, that was nearly three times the height of an average man and 12 metres long.

The interesting part is that though people in India kept on bumping into fossilised tooth and bone fragments of these large animals for centuries yet nobody knew about dinosaurs. Some thought that these bones, skeletal remains and tooth came from dragons. In Gujarat, tribal worshipped oblong stones, considering them to be a sacred deity, while they actually were fossilised dino eggs. The Kutch region itself has yielded more than 2,000 such eggs. In India more than 10,000 eggs have been documented with all of them occurring in ancient soil horizons and other sediments interbedded with the volcanic outpourings of the Deccan Traps. The egg fossils have been reported from Gujarat, Rajasthan, Maharashtra, Madhya Pradesh, Andhra Pradesh, Tamil Nadu and Karnataka.

Ashok Sahni, an eminent palaeontologist from Panjab University, Chandigarh, who has been associated with dinosaur studies in India, has an interesting anecdote to narrate. "In October 1982, when I was attending a seminar in Ahmedabad, a young Geological Survey of India (GSI) officer came to inquire about a spherical 18 cm object from me. Such objects were apparently unearthed during the blasting operations of the then existing ACC cement factory at Balasinor and the "cannon balls", as they were commonly known, decorated the shelves of the mine manager’s office. We recognised the "cannon ball" to be dinosaurian egg and within a year’s time, GSI unearthed several hundreds of them from the area," he recalls.

Thousands of fossilised dinosaur eggs have been reported from Pisdura, Maharashtra. Ostensibly, a nesting site for sauropods. Villagers here while ploughing also unearthed fossilised remains of cattle and other mammals. This point out to the fact that it might have been the ‘youngest’ egg find till date. Perhaps, that region was the last place to have harboured dinosaurs before they actually disappeared giving way to birds and mammals.

India, at that time, was not what it is today. The Indian landmass was in the southern hemisphere then. Later, the landmass made its journey northwards nearly 60 million years ago colliding into the then Asia and giving rise to Himalayas. A place of interest is Um Shorengkew in Meghalaya where Himalayas might have buckled backwards after collision as dinosaur fossils have been excavated from here an otherwise rare occurrence from the Himalayan region.

Why India?

Sahni observes: "India has the largest number of eggs and nests from a single time interval (68 to 65 million years ago) representing the Lamenta Formation sediments which are believed to have been deposited at the time of Deccan volcanic activity. Other countries, such as China, Mongolia and the USA have several horizons from which dinosaur eggs have been isolated, but not from a single formation, as in India. What actually counts in the preservation of eggs is really not how many eggs were laid but how many of these were preserved as fossils. The process of fossilisation is selective and as we all know eggs tend to rot easily. For preservation of the Indian dinosaur eggs, it is believed that frequent flooding and covering of nests and eggs by sediments led to better preservation. There is evidence of flooding in the Lamenta sediments where nests have been found. On the surface on which the nests and eggs are exposed, we find pebbles of fairly large size, which could only have been brought there by flood waters."

Prithiraj Chungkham, a gold medalist geologist and Senior Basin Researcher currently based in Singapore, avers that dinosaurs could have travelled thousands of miles to nest or lay eggs in India.

"Findings of fossilised dinosaur eggs, along with bones, are rare where one can conclude with a very high degree of certainty that they were preserved in situ without having been subjected to any weathering and transportation. In bone-only finds, which now occur in almost all continents, there is still a possibility that the bones had suffered weathering and transportation before being preserved as it can withstand some degree of both the nature agents unlike the eggs. Thus any sedimentary horizon yielding dinosaur ‘bones-only’ does not necessarily represent the prevailing environment where the dinosaurs lived. In contrast, any sedimentary horizon yielding dinosaur eggs, with or without bones, will content useful geological signatures which will throw plenty of lights on the prevailing environmental conditions where the dinosaurs lived and died.

An intriguing question is why these dinosaur eggs sites are so rare and not widespread as the bone sites? Is it simply and only because eggs did not get preserved as easily as the bones or did dinosaurs travel thousands of miles to specific nesting sites, like the certain modern-day salmon fish, which swims all the way from the sea upstream along the rivers to specific fresh water sites to lay eggs?

Various theories are being postulated as to why dinosaurs became extinct. Scientists have suggested various theories from sea-level changes, vulcanism, meteorite strike to biotic extinction. What actually happened no one knows. However, the most accepted theory is that of a meteorite strike.

Rajeev Patnaik, principal investigator, Department of Science and Technology and National Geographic Project, opines that dinosaurs might have become extinct when an asteroid with a diameter of 10 km hit Central America 65 million years ago, forming the Chicxulub crater in Yucatan Peninsula, Mexico. "If we observe closely, the Indian Deccan traps are bang opposite the area of strike on the globe. This asteroid hit could have induced heavy volcanic activity in India resulting in the death of dinosaurs," he says. Patnaik is actively involved with the dinosaur gallery that is coming up in Chandigarh though he himself is a hominid expert. (see box).

Samples collected from rock strata where dino fossils have been found, indicate a very high level of iridium content, almost 30 times more than that is present under normal circumstances. There are two main sources of iridium, the main source comes from outer space in the form of cosmic dust and a second source is the Earth’s core when there are eruptions of certain types of volcano. So in any case, either dinosaurs became extinct due to a meteorite hit or due to intense volcanic activity induced by the strike.

Prithiraj adds pragmatically: "What wiped out the dinosaur? Was it meteorites from the space or extensive volcanism or drastic climate change or combination of all these calamities? Or simply was it something that dinosaurs were so dependent upon ran out of stock? Careful investigation of the dinosaur egg-bearing rocks will certainly throw lights on these questions, which will not only enlighten the scientific minds but also the general public. Discoveries of such rare sites of unique importance by our hardworking geoscientists deserves general applaud and better support from our government and financial institutes."

The general view among the geological fraternity is that dinosaurs died and birds evolved from them. So do dinosaurs now exist as birds? Or have they been buried down forever as fossils. That’s a dino-sized enigma concealed under zillion layers of rocky strata.