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A swimming dinosaur: The revealing tail of Spinosaurus aegyptiacus

How did the enigmatic Spinosaurus aegyptiacus or ‘Egyptian spine lizard’ live day to day 112 to 93.5 million years ago? A new desert discovery has revealed that this species of spinosaurs was a powerful swimming predator.

In this April 2020 Nature video, paleontologist Nizar Ibrahim describes the experience of discovering the dinosaur’s surprising tail bones in the rock and sand of the Sahara desert, an area he calls the “river of giants,” “the most dangerous place on Earth,” and “a true predator’s paradise.”

digging up a tail bone
He also explains the technologies that helped test if the tail could successfully propel a large carnivorous beast. More about this “river monster” from the paper’s abstract:

It has recently been argued that at least some of the spinosaurids—an unusual group of large-bodied theropods of the Cretaceous era—were semi-aquatic, but this idea has been challenged on anatomical, biomechanical and taphonomic grounds, and remains controversial. Here we present unambiguous evidence for an aquatic propulsive structure in a dinosaur, the giant theropod Spinosaurus aegyptiacus.

tail shape mockups for testing

This dinosaur has a tail with an unexpected and unique shape that consists of extremely tall neural spines and elongate chevrons, which forms a large, flexible fin-like organ capable of extensive lateral excursion. Using a robotic flapping apparatus to measure undulatory forces in physical models of different tail shapes, we show that the tail shape of Spinosaurus produces greater thrust and efficiency in water than the tail shapes of terrestrial dinosaurs and that these measures of performance are more comparable to those of extant aquatic vertebrates that use vertically expanded tails to generate forward propulsion while swimming. These results are consistent with the suite of adaptations for an aquatic lifestyle and piscivorous diet that have previously been documented for Spinosaurus.

spinosaurus teeth
Related reading at National Geographic: Bizarre Spinosaurus makes history as first known swimming dinosaur.

This animated video, written by Ibrahim, will need to be updated: The ferocious predatory dinosaurs of Cretaceous Sahara.

Does this Spinosaurus skeleton need to be updated, too?

Watch these related paleontology videos next:
How scientists solved this dinosaur puzzle
• What are mosasaurs?
• Dreadnoughtus: A New Dinosaur Discovery
• Why are there oyster shells in the ‘Chalk Pyramids’ of Kansas?

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