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  • Devayani Khare

The Age of the Dinosaurs

Updated: Mar 14

In January 2022, several news channels celebrated India's very first geological park to be built in Lamheta, near Jabalpur, in Madhya Pradesh. While most articles mentioned how in 1928, William H. Sleeman discovered a dinosaur fossil in Lamheta - hence, the choice of site, few dug deeper into the incredible age of the dinosaurs. This excerpt hopes to do just that!


Lamheta is not just well known among geologists for the first dinosaur fossil discovery. It also lent its name to the distinct sedimentary limestone beds found across the Deccan Traps, stretching from Madhya Pradesh, to Maharashtra and Gujarat. Over decades, this limestone belt - the Lameta formation has yielded some of India's most spectacular fossil records, especially that of dinosaurs.


In the Central India river basins, the geological record from the age of the dinosaurs is quite incomplete - it has either been eroded away, or there wasn't enough sediment laid down to preserve any fossils. All the dinosaur fossils we've found, have been dated to within a ~150 thousand year span of the late Cretaceous - too limited to explain dinosaur diversity or evolution. The few fossils (and stories) we've unearthed, however, are fascinating.


HOW DO FOSSILS FORM?



“To greet each day ossified; Like fossil remains forgotten beneath the feet of something more lively.” – Taylor Patton Fossils are the dead remains or evidence of past organisms. These not only include impressions of skeletal or structural features, but also nests, burrows, footprints or poo (fossil poo is known as coprolite) of ancient creatures. Fossilization is a rather rare process, most organisms simply die and their remains rot away. Occasionally, if an organism dies and is quickly buried under layers of sediment, volcanic ash, or a peaty bog, the layers harden or lithify and leave behind an impression - a fossil. For instance, ancient marine creatures have left behind shell-like impressions. Often dissolved minerals find their way into the spaces where the creatures were buried, and crystallize. Teeth, bones, shells, wood, are often preserved this way and are known as 'petrified' fossils - those that have turned to stone. Specimens preserved in amber (like the mosquito from Jurassic Park!) or ice (like the 40,000-year-old baby mammoth Lyuba) are also considered to be fossils and are incredibly rare occurrences of mummification - where soft tissues are preserved, as rapid burial and low oxygen prevents decomposition.


BOOT THE T-REX, HERE'S THE TITANOSAURUS INDICUS


Named after the mythological Titans, the Titanosaurus indicus was among the largest creatures to have walked the Earth.


In 1828, during a fossil-hunting expedition, Capt. William Henry Sleeman of the Bengal Army collected a few vertebrae from the Lameta formation near Jabalpur. Yet it was only after the bones passed through the hands and scrutiny of a series of palaeontologists, from Spilsbury (1828), James Princep (1832), Thomas Oldham (1862), to Hugh Falconer (1868), that they were ascertained as reptilian bones. Over a decade later, Richard Lydekker studied these bones along with others found by H.B Medlicot from the same region and established the type species - Titanosaurus indicus, the first dinosaur to ever be described from India. Soon after, he also described the Titanosaurus blanfordi.


The two titanosaurus (T. indicus and T. blanfordi) must have roamed the Earth around 70 million years ago.


* Note: While the movie Jurassic Park helped bring dinosaurs into popular imagination, not all dinosaurs lived only in the Jurassic era (~201 - 145 million years ago/mya). They were alive through the Triassic (~252-201 mya), the Jurassic and the Cretaceous (~145-66 mya). These two species described from India, along with several others, were late Jurassic to end-Cretaceous dinosaurs.


The Titanosaurus indicus holotypic distal caudal vertebra, from a publication by Hugh Falconer.

(A revision of Titanosaurus Lydekker (Dinosauria – Sauropoda), the first dinosaur genus with a ‘Gondwanan’ distribution, 2003)

Image credit: Public Domain


The Curious Case of Lost & Found Fossils


By the end of the 20th century, the remains of the T. indicus were untraceable. When Dhananjay Mohabey (aptly @DinoMohabey, on Twitter), tried to locate the specimens, he realised that they were not lost just forgotten - the Geological Survey of India (GSI) had not carried out official inventories for a huge number of fossils. In 2012, he and Subhasis Sen recovered holotype vertebrae from Lydekker's 1878 batch of fossils.


Sadly, so many other fossils haven't been as fortunate. In the 1930s, over 400 crates of fossils, including many dinosaur remains, were shipped out of India by the British. The GSI's efforts to retrace and recover the collections haven't been too successful. There have also been thefts from field sites and museums, which beggar India's relatively poor fossil record. We cannot fathom what we may have lost, and the stories of deep time that have gathered dust in distant archives. Time will tell.


ANACONDA MEETS JURASSIC PARK


The Sanajeh snake about to attack a Titanosaurus hatchling. Credits: Sculpture by Tyler Keillor and original photography by Ximena Erickson; image modified by Bonnie Miljour - Benton MJ (2010) Studying Function and Behavior in the Fossil Record. PLoS Biol 8(3): e1000321. doi:10.1371/journal.pbio.1000321.g001, via Wikimedia Commons, CC-BY.


Nope, that sensational title isn't original - it is borrowed from some coverage on a most fascinating study published in 2010. Authored by Jeffrey Wilson, Dhananjay Mohabey, Shanan Peters, and Jason Head, this PLOS Biology paper was based on the discovery of an unusual fossil that changed our understanding of both dinosaurs and snakes.


In 1987, Mohabey unearthed the specimens in question at Dholi Dungri, Gujarat (part of the Lameta formation), and the sediment covered blocks were near inscrutable. Over time, he was able to discern dinosaur eggshells and limb bones. It wasn't until 2001 when Wilson visited his office and saw the specimen that they were able to identify the distinct vertebral locking mechanism in snakes, that they realised just how incredible the specimen was.


Formal agreements for study, fossil preparation, field reconnaissance followed, and a snake researcher and geologist, Head and Peters, were brought onboard. In March 2010, their efforts finally saw the light of day. It had taken over two decades to decode the drama that had been captured in the fossil blocks - clearly, deep time does not yield its secrets so easily.


(Left) The fossil of a snake (Sanajeh indicus) discovered among a partial clutch of three titanosaurus eggs. (Right) An artist's interpretation of the fossil blocks.

Image credit:https://doi.org/10.1371/journal.pbio.1000322


What they'd found were the remains of a near-complete snake preserved in the nest of a Titanosaurus - the snake was coiled around a recently hatched egg, and a hatchling sauropod. As the remains of other snakes near egg clutches were found at the same site, one can surmise that the snake, later described as Sanajeh indicus, fed on young dinosaurs.


The preservation of the bones and the delicate structures like the eggshells and the snake's skull indicate that rapid entombment occurred. The sedimentation was unusual, and perhaps a storm or a pulse of sand, caused this dramatic moment to be frozen in time.


The snake named Sanajeh indicus, has a gape that isn't as wide as that of modern snakes - the gape provides some insights into how these creatures evolved to eat prey larger than themselves. Interestingly, the Sanajeh also adds to other evidence that suggests the Indian subcontinent might have been tied to southern landmasses that separated from Gondwanaland, for far longer than our current estimates.


OTHER DINOSAUR FOSSILS

Over 20 dinosaur species have been unearthed from India (most of them from the Lameta formation, but some from other geological strata as well), some of which bear resemblance to fossils found in Madagascar - evidence of these two landmasses once being connected. Debate still rages about the nomenclature of a few dinosaurs, and more studies will help us better classify the fossils we have. Among India's most renowned dinosaurs is the Rajasaurus narmadaensis (you guessed it, found along the Narmada river!), discovered in 2003 by Ashok Sahni - you can read more about this carnivorous dinosaur in this article.



One more theory - Bizarro.com comics


The demise of the dinosaurs: The most widely accepted reason for the demise of the dinosaurs is the asteroid - the impact of the Chicxulub crater on Mexico's Yucatan peninsula, has been dated to around ~66 million years ago. The climate disruption from this Cretaceous-Paleogene event wiped out over 75% of plant and animal species. While most say the dinosaurs went extinct, research points towards modern-day as descendants of the dinosaurs. The dinosaurs still fly (well, most of them) among us!


In India, the ~66 million year mark is significant - the Indian plate was moving over the Reunion hotspot, and the Deccan volcanism was at its fieriest. Apart from the climate change after the Chicxulub asteroid, the Deccan volcanism would also have had a severe impact on the dinosaurs hitching a ride north on the Indian landmass.


For the Twitterati: I'd also done a short Twitter thread comparing the ages of (India's) dinosaurs and the geological history of the Indian Plate.


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