Debating the Spinosaurus: Terrestrial or Aquatic?

Written by Damien Rudy

Spinosaurus art by Arvalis

Spinosaurus Aegyptiacus is one of the most beloved dinosaurs in the paleontology community and yet, it continues to be found under the spotlight of controversy. The Spinosaurus is a dinosaur that lived during the Late-Cretaceous period (About 99 to 93.5 million years ago) in what is modern day Northern Africa (Locations such as Egypt). It is believed to be one of the larger carnivorous dinosaurs and sports a signature sail upon its back, giving it a unique and recognizable look. 

Spinosaurus is believed to have eaten marine life such as fish as the cornerstone of their diet, but the aforementioned controversy derives from the manner in which the dinosaur hunted said marine life. Did it dive after fish on the coast and in large rivers? Or did it perhaps wade into the shallows to catch fish? For that answer, paleontologists must speculate, which inevitably leads to arguments. 

Spinosaurus was first discovered in 1912 in  the Bahariya formation of Egypt by German paleontologist Ernst Stromer. These original remains were very incomplete, leaving a lot of this creature's structure up for debate. Stromer concluded that Spinosaurus was a large, terrestrial theropod similar to well known dinosaurs like Tyrannosaurus and dinosaurs it shared its habitat with such as Carcharadontosaurus. The original bones were then, regrettably, destroyed in the midst of World War 2 during a British bombing raid in 1944. The Spinosaurus at this point was seen as a fully terrestrial theropod due to limited evidence of any other possibility. About 70 years later, a paleontologist by the name of Nizar Ibrahim reconstructed the Spinosaurus. This reconstruction allowed the possibility of a semi-aquatic lifestyle for the Spinosaurus. This reconstruction kicked off the Terrestrial vs. Semi-Aquatic debate among paleontologists. 

4 years later, in 2018, Ibrahim’s team found evidence of the Spinosaurus actually possessing a tail paddle (in the form of tail vertebrae with large spines), which would further back the semi-aquatic argument for the Spinosaurus. It was also noticed that Spinosaurus’ bones are quite dense, much like aquatic creatures such as Sea Cows. These dense bones may have acted as a ballast, allowing Spinosaurus to submerge itself underwater. A paleontologist by the name of Paul Sereno backs up the dense bones argument as an adaptation for semi-aquatic life. Paul Sereno himself however, would do a double take on this outlook, later supporting the argument of a more terrestrial lifestyle. Paleontologists also have reported that the Spinosaurus likely found its home in freshwater habitats, supported by the material and location the bones were found in (freshwater silt). 

Paul Sereno in studies submitted to the University of Chicago, (where he works as a professor) states that the dense bones were suited to, “Support the great weight of the beast”, Sereno went on to admit a mistake he made in his original studies, with Sereno and his colleagues originally miscalculating the weight proportions of the beast, they believed that its center of gravity identified it as traveling on all fours, however, the group of paleontologists didn’t bring the Spinosaurus’ lungs into account. After they applied the weight of its lungs, they found that the Spinosaurus’ center of gravity was probably closer to its hind legs, allowing bipedal travel like other large carnivorous dinosaurs. 

These arguments have even led to jokes and spoofs of the Spinosaurus. Now, every time new research emerges of Spinosaurus, fans make a joke, stating that, “Spinosaurus got nerfed again!” The most famous, “Nerfed Spinosaurus” is a spoof known as Spinofaaurus Vulgaris by Chris Masna, an elephant seal inspired work, making a mockery of the communities assumptions and indecisiveness regarding the Spinosaurus.

More evidence continues to be revealed for both sides as the paleontology community continues to divide in this debate. As you’d expect, Paul Soreno still backs the terrestrial theory and Nizar Ibrahim remains on the aquatic side. This debate (unsurprisingly) will likely perplex paleontologists forever, all in all, creating the most controversial dinosaur.