They roamed our planet over 66 million years ago, yet dinosaurs continue to teach us new things about life on Earth.
By S Reid-Collins and Caroline Brogan
The Late Cretaceous landscape of North America. (Davide Bonadonna)
The Late Cretaceous landscape of North America. (Davide Bonadonna)
We take a journey through time to explore the work of the Imperial researchers building a bigger picture of the lives – and deaths – of the dinosaurs which walked, flew and swam on Earth for over 165 million years.
Dinosaurs roamed the Earth in the Mesozoic Era, which is split into the Triassic, Jurassic and Cretaceous periods. They first emerged during the Triassic period around 245 million years ago. At the time, all continents were part of a single land mass – the supercontinent Pangea.
The climate was hot and dry, and much of the land was covered in large deserts. Because of this, there was little diversity between the animals and plants in different areas during the first period of the dinosaurs.
174– 164million years ago: Mid Jurassic Period
Our journey through Imperial’s research begins in the Middle Jurassic Period, as the supercontinent Pangea was splitting into separate continents – Laurentia in the North and Gondwana in the South. Rainfall increased due to the seas forming between the landmasses which allowed lush ferns and forests to grow.
During this period, groups of land animals diversified as they spread across the globe and some of the major dinosaur groups emerged, including brachiosaurs andmegalosaurs.
Dinosaur fossils from the Mid-Jurassic epoch are relatively rare, but new fossils and species from the period are still being discovered, allowing researchers to gain a greater understanding of the evolution of life on Earth.
‘Amazing dragon fromLingwu’ In 2018, researchers at Imperial, the Chinese Academy of Sciences, and UCL found the world’s oldest neosauropod species in Lingwu – a city in northern China. The dinosaur, named Lingwulong shenqi (the ‘amazing dragon from Lingwu’), is a member of the diplodocoid sub-group and would have been 15 metres long.
The researchers foundpartial skulls, vertebrae, shoulders, and ribs of between seven and ten sauropods-ranging from young to adult- and created a composite image of what L.shenqiwould have looked like.
The fossils were dated at 174 million years, 15 million years older than anydiplodocoidpreviously found, and were the first to be found in China. Scientists had previously believed thatdiplodocoidswere absent from China, having evolved after eastern Asia split from Pangea 160 million years ago. The new fossils challengethis, andindicate thatdiplodocoidsdispersed to eastern Asia long before it was separated from Pangaea.
Co-author Dr Philip Mannion, from Imperial’s Department of Earth Science and Engineering, said the discovery was "doubly unexpected. Not only is Lingwulong the oldest member (of this group), but it's the first ever from Asia. Until now, we thought that neosauropods didn't enter Asia during the Jurassic.”
The fossilscould help us understand how dinosaurs and other animals evolved and dispersed through the ancient supercontinent Pangaea.
Who were the sauropods?
Sauropods were plant eaters and the largest of all dinosaurs, with some species reaching 30 metres long. Theseherbivores walked on four legs and had small heads with long necks and tails. Sauropods are part of theSaurischia(‘lizard-hipped’) dinosaur group, one of the two major lineages of dinosaurs. The other group isOrnithischia(‘bird-hipped’). The most famous sauropods include the Diplodocus and Brachiosaurus.
163 – 145million years ago: Late Jurassic Period
By the end of the Jurassic Era, large herds of herbivorous dinosaurs dominated thelandscapeas the flourishing flora allowed large plant-eating dinosaurs to thrive.
Earliest relative of Brachiosaurus dinosaur found in France
In 2017, scientistsfrom Imperialre-examined an overlooked museum fossilwhich was originally found in France in 1930and discovered that itwasthe earliest member of thetitanosauriformfamily– a diverse groupof sauropod dinosaurs which included some of the largest animals ever to have walked on Earth.
The fossil, namedVouivriadamparisensisby Imperial researchers and their colleagues in Europe, is thought to be 160 million years old, making it the oldest knowntitanosauriformfossil to be discovered.
Titanosauriformswere sauropod dinosaurs which lived from at least the Late Jurassic Period to the end of the Cretaceous Period. The three main groups making uptitanosauriformsare theBrachiosauridae, which includes the Brachiosaurus, theEuhelopodidaeand theTitanosauria.
V. damparisensiswas identified as abrachiosauridsauropod dinosaur. It weighed around 15,000 kilograms and was 15 metres long.
A lack of fossil records means that it has been difficult for scientists to understand the early evolution oftitanosauriformsand how they spread out across the planet. The re-classification ofV. damparisensisas an earlytitanosauriformwill help scientists to understand the spread of these creatures during the Early Cretaceous period-a laterperiod of time, after the Jurassic, around 145to100 million years ago.
Dr Philip Mannion, lead author of the study from the Department of Earth Science and Engineering at Imperial, said: “Vouivriawould have beenaherbivore, eating all kinds of vegetation, such as ferns and conifers. This creature lived in the Late Jurassic, around 160 million years ago, at a time when Europe was a series of islands. We don’t know what this creature died from, but millions of years later itstill providesimportant evidence to help us understand in more detail the evolution ofbrachiosauridsauropods and a much bigger group of dinosaurs that they belonged to, calledtitanosauriforms."
Crocodilians
Dinosaurs weren’t the only creatures thriving in the Jurassic period.
Crocodilians lived alongside the dinosaurs, evolving into a variety of different species including smaller and larger land species and large sea swimming species which reached up to 12 metres long.
They came in all shapes and sizes, including giant land-based creatures such as Sarcosuchus, which reached 12 metres in length and weighed up to eight metric tonnes.
145 million years ago: Jurassic/Cretaceous boundary
The heyday of the crocodilians ended 145 million years ago as the changing climate and fluctuating sea levels caused a mass extinction event – 79 million years before the asteroid impact which destroyed the dinosaurs.
Changing sea levels led to a reduction of shallow marine environments such as swamps and lagoons which were the primary hunting grounds of many species of crocodilians. Around 80 per cent of crocodilian species were wiped out in the extinction event between the Jurassic and Cretaceous periods.
Researchers at Imperial found that this extinction event coincided with the origin of modern marine turtles, whose ancestors were hunted by crocodilians.
Dr Jon Tennant, lead author of the study from the Department of Earth Science and Engineering at Imperial, said: “This major extinction of crocodilians was literally a case of out with the old and in with the new for many species. Marine turtles, the gentle, graceful creatures of the sea, may have been some of the major winners from this changing of the old guard. They began to thrive in oceans around the world when their ferocious arch-predators went into terminal decline.”
145 – 66 million years ago: Cretaceous Period
The Cretaceous Period was the longest of the three periods of the Mesozoic Era, spanning for over 79 million years. During this period, the continents completely separated, causing dinosaurs and other life forms to evolve independently of each other.
Ancient Rainforest in Antarctica
An international team of geoscientists, including Imperial researchers, found evidence that rainforests existed near the South Pole 90 million years ago, during the heyday of the dinosaurs. This suggested that the climate was a lot warmer than previously thought.
The researchers discovered forest soil from the Cretaceous period just 900km away from the South Pole. The soil contained preserved roots, spores and pollen. The findings suggest that average temperature of the region was 12 degrees centigrade and that there was no polar ice cap.
Co-author Professor Tina van deFlierdt, from the Department of Earth Science & Engineering at Imperial, said: “The preservation of this 90-million-year-old forest is exceptional, but even more surprising is theworld it reveals. Even during months of darkness, swampy temperate rainforests were able to grow close to the South Pole, revealing an even warmer climate than we expected.”
100 – 66 million years ago: Late Cretaceous Period
Despite the changing climate, dinosaurs were thriving prior to the asteroid impact which wiped out 75 per cent of life on Earth 66 million years ago.
While scientists largely agree that an asteroid impact was responsible for the demise of the dinosaurs, there has been debate around whether dinosaurs were flourishing or if they were already headed towards a mass extinction event that would have wiped them out regardless.
Researchers had previously used fossil records and mathematical modelling to find that dinosaurs were already in decline due to millions of years of climate change, with the number and diversity of species already falling prior to the asteroid impact which ultimately triggered the mass extinction event.
Howeverin 2019 a team of researchers from Imperial, UCL and the University of Bristolmodelled the changing environment anddinosaur species distribution in North Americaand foundthat dinosaurs were likely not in decline before the meteoritehit.Thestudyfound that changing conditions for fossilisation means that previous analyses of the number of dinosaur species may have been underestimated.
Lead authorDr Alessandro Chiarenza said the “dinosaurs were likely not doomed to extinction until the end of the Cretaceous, when the asteroid hit."
66 million years ago: the asteroid
66 million years ago, an asteroid hit present-day Mexico and heralded the the end of Cretaceous period.
Despite the rise in volcanic activity and climate change, Imperial researchers found that it could only have been the asteroid impact that killed the dinosaurs 66 million years ago.
Researchers had previously suggested that tens of thousands of years of volcanic eruptions at the Deccan Traps, in modern day India, may have been the cause of the large extinction event.
Researchers at Imperial used traditional geological markers of climate change and powerful mathematical models to determine which factor led to the demise of the dinosaurs. By combining these with the environmental factors different species needed to thrive, such as rainfall and temperature, researchers found thatonly the asteroid strike wiped out all potential dinosaur habitats, while volcanism left some viable regions around the equator.
Lead researcher Dr AlessandroChiarenza, who conducted this work at Imperial, said:“Our study confirms, for the first time quantitatively, that the only plausible explanation for the extinction is the impact winter that eradicated dinosaur habitats worldwide.”
The asteroid that killed the dinosaurs hit Earth at the ‘deadliest possible’ angle
Simulations from Imperial researchers found that the asteroid hit the Earth at the worst possible angle for the dinosaurs.
Theasteroid struck the Earth at 60 degrees,which maximised theamountof climate-changing gases thrust into the upper atmosphere.
Research found that the angle of the final asteroid impact atChicxulubin Mexico increased the hazardous amounts of debris being scattered through the Earth’s atmosphere, leading to the impact winter which killed 75 per cent of life on Earth.
Lead researcher Professor Gareth Collins, of Imperial’s Department of Earth Science and Engineering, said: “For the dinosaurs, the worst-case scenario is exactly what happened. The asteroid strike unleashed an incredible amount of climate-changing gases into the atmosphere, triggering a chain of events that led to the extinction of the dinosaurs. This was likely worsened by the fact that it struck at one of the deadliest possible angles.”
Life after the dinosaurs
Despite the destruction, the asteroid’s ‘ground zero’ grew to house a thriving ecosystem, including microscopic plants that supported a diverse community of microfossils in the surface waters and on the seafloor.
Withinjust30,000 years of impact, Mexico’s Chicxulub crater fostered a thriving ecosystem - a much faster recovery than manyimpactsites around the world.By contrast, it took other areas on the planet, such as the North Atlantic and other areas in the Gulf of Mexico, over 300,000 years to recover to the same levels.
In April and May 2016, an international team of scientists undertook an offshore expedition and drilled into part of the Chicxulub impact crater. Their mission was to retrieve samples from the rocky inner ridges of the crater - known as the ‘peak ring’ - drilling up to 1,335 metres below themodern-day sea floor to understand more about the ancient cataclysmic event.
For her work on the crater,ProfessorMorganbecame the first UK recipient of the Barringer Medal.
“This medal is an exceptional award that recognises an outstanding scientist. Professor Morgan’s work on the “Crater of Doom” is both exciting and inspiring,” said Professor Mark Sephton, Head of the Department of Earth Science and Engineering. “The evidence she has uncovered provides an insight into one of the most cataclysmic events in Earth history.”
What became of thecrocodilians?
While the mass extinction event wiped out most of the dinosaurs, manycrocodilianssurvived. Imperial researchersfound that theCretaceous-Paleogeneextinction event hada positive impact on the remaining species, which were able to branch outinto habitats that had become unoccupied.
Cooling climates have since led to a decline in the number ofcrocodilianspecies, and only 23 remain today.
“Crocodiliansare known by some as living fossils because they’ve been around since the time of the dinosaurs,” saidDr Philip Mannion, joint lead authorof the study.
“Millions of years ago these creatures and their now extinct relatives thrived in a range of environments that ranged from the tropics to northern latitudes and even deep in the ocean. However, all this changed because of changes in the climate, andcrocodiliansretreated to the warmer parts of the world.
“While they have a fearsome reputation, these creatures are vulnerable and looking back in time we’ve been able to determine what environmental factors had the greatest impact on them. This may help us to determine how they will cope with future changes.”
Moving forward
Imperial's award-winning research continues to be instrumental in tracking and understanding the dinosaurs’ demise from dominance to doom.
By looking at the events leading up to the extinction of dinosaurs and other species, scientists can better understand how the changing climate impacts current species.
As we learn about what led to the extinction of the once-dominant reptiles, we discover more about the world around us and the universe we live in.
Built withShorthand