Spinosaurus aegyptiacus: The First Known Aquatic Dinosaur
A species of carnivorous dinosaur called Spinosaurus aegyptiacus used tail-propelled swimming locomotion to hunt for prey in rivers, according to a new analysis of the world’s only existing skeleton of this ancient predator, found in the Kem Kem region of the Moroccan Sahara.
Spinosaurus aegyptiacus is a giant theropod dinosaur that lived about 95 million years ago (Cretaceous period) in what is now North Africa.
In a previous study, this creature had been identified as a fish-eating dinosaur with adaptations for an amphibious lifestyle, supported by its relatively short hindlimbs, wide feet, dense bones and elongated jaws studded with conical teeth.
However, suggestions that it may have been a truly water-dwelling dinosaur were met with considerable opposition, in large part because the partial skeleton provided little to no evidence of the propulsive structure needed to move such a giant dinosaur through water.
A research team led by National Geographic Explorer and University of Detroit Mercy paleontologist Nizar Ibrahim to the Kem Kem site where parts of the Spinosaurus aegyptiacus skeleton had first been uncovered in 2008.
Between 2015 and 2019, the researchers recovered many more fossils, including a remarkably complete, fin-like tail capable of extensive lateral movement and characterized by extremely long spines.
They then used photogrammetry to digitally capture the anatomy of the tail of Spinosaurus aegyptiacus.
To quantitatively assess the performance of the tail, they made a flexible model and attached it to a robotic system that mimics swimming movements.
They then compared the swimming performance of the model Spinosaurus aegyptiacus tail to those from crocodiles, newts and other dinosaurs.
The results were fully consistent with the idea of a truly water-dwelling, tail-propelled, river monster.
“This dinosaur was actively pursuing prey in the water column, not just standing in shallow waters waiting for fish to swim by. It probably spent most of its life in the water,” Dr. Ibrahim said.
“This new discovery changes our current understanding of dinosaurs and reflects Dr. Ibrahim’s boundless curiosity and dedication to uncovering the secrets of the Sahara’s dinosaurs,” added Alex Moen, vice president of explorer programs at the National Geographic Society.
“His work is at the nexus of science and exploration, and embodies the unique role National Geographic has in illuminating the wonder of our world.”
This research, supported by a grant from the National Geographic Society, is described in a paper in the journal Nature.
N. Ibrahim et al. Tail-propelled aquatic locomotion in a theropod dinosaur. Nature, published online April 29, 2020; doi: 10.1038/s41586-020-2190-3