Not just water and sky, dinosaurs also lived in water, a new study has found!

Dinosaurs not just dominated land and sky, but also water! A new research paper has argued that while dinosaurs dominated the land and the sky during the cretaceous period, between 145 to 66 million years ago, the ferocious creatures also dominated the water, according to a news published by the Harvard University. The paper, published in Nature on Wednesday, cited fossil evidence and robotically controlled models which have been created by co-authors Stephanie E Pierce and George V Lauder, professors of organismic and evolutionary biology at Harvard.

According to the Harvard news, recent fossil evidence has pointed out that Spinosaurus Aegyptiacus was an aquatic dinosaur. The species, one of the largest carnivorous dinosaurs known to man, had a giant fin tail as well as a centre of gravity which was highly suitable for swimming, the university report said.

The paper also shares the modelling by the Harvard co-authors, who showed that the large and flexible fin tail, which is unique among dinosaurs, would have given the species a propulsive thrust when inside the water, like the tail of a salamander or a crocodile.

The university report quoted co-author Pierce as saying that finding new fossil evidence was highly important for them to make their argument since most of the earlier fossil evidence of this species had been destroyed during World War II.

The lead author of the paper, a Paleontologist at the University of Detroit, Nizar Ibrahim had located more traces of the dinosaur species in 2014 in Morocco, and he went back to the country in 2018 to carry out the successful excavation of extensive remains of Spinosaurus. The excavated fossil included tail vertebrae with spines as long as a metre, which seemingly formed an expanded paddle. This raised questions about the possible purpose of the tail.

Pierce said that the working thesis in this regard was that the dinosaur used the tail to swim. She was approached by Ibrahim and his team to test their idea. Pierce, who is a curator of vertebrate paleontology at the Museum of Comparative Zoology, was fascinated by the tail which was longer than five metres.

She said that in this particular species, there were several features that stood out, including a fin-like structure not found in any other dinosaur so far, the university report said.

Pierce then roped in fish bio-mechanist Lauder and together, they started working on building a model of the dinosaur’s tail, along with the top fin that would cover the metre-long spines.

Lauder was quoted by the university report as saying that they cut simple plastic models of different tails and attached them to the remote controller, using which they could move the tail back and forth. With this movement, they could make the Spinosaurus ‘swim’ and could effectively quantify the difference in the swimming of the Spinosaurus and the tails of other dinosaurs.

Earlier as well, some paleontologists had been of the view that Spinosaurus could swim, but the idea was not well received as some scientists believed that the data had been “over interpreted”, according to Pierce. Some others had worked out mathematical experiments to prove that a Spinosaurus would not swim. But now, Pierce said, the discussion is over since the fin is not a conjecture. Moreover, she said, the centre of gravity of the dinosaur species would most likely tip the giant predator forward if it lived on the land.

Apart from this, there is also additional evidence supporting the theory that Spinosaurus was an aquatic creature. The new fossils excavated by Ibrahim have been found in freshwater sediment, along with the fossils of other animals, like coelacanths, a large fish which has existed since the time of the dinosaurs.

Pierce was quoted as saying that the debate has now reached an end, since the team has gathered enough evidence to prove that Spinosaurus was in fact a highly adapted creature of the water.

Trying to answer the question about the speed of the Spinosaurus, Lauder said that since the species was huge, it probably did not zip through the water. The remains which have been excavated belong to a small Spinosaurus, but it still was 10 metres long. Lauder and Pierce said that at a slow, steady pace, the dinosaur could probably swim at a speed of 2.5 metres per second.