Debate heats up over swimming ability of bizarre-looking Spinosaurus

An illustration of a Spinosaurus wading in the water and hunting for fish.

(Image credit: Nicholls2020)

The wild-looking Spinosaurus may not have been the Michael Phelps of dinosaurs, as was recently claimed, but rather more like a casual bathing beauty that preferred to wade gracefully in the shallow zone, a new study suggests.

That's not to say Spinosaurus couldn't swim: It could. But it wasn't the "highly specialized aquatic predator" that could efficiently chase prey through the water, as it was made out to be in a big 2020 study published in the journal Nature, the researchers of the new study said.

Spinosaurus, which lived about 112 million to 94 million years ago during the Cretaceous period, has baffled scientists since its 1915 discovery in North Africa. At more than 50 feet (15 meters) in length, it was as large as a Tyrannosaurus rex and had large projections sticking out of its back, which may have formed a skin-covered sail. The oddball's crocodile-like snout and teeth indicated that it hunted fish; chemical analyses of isotopes (versions of an element) and fossil finds confirmed it ate fish as well as snacked on dinosaurs and pterosaurs.

Spinosaurus' habits are challenging to decipher because there are few fossils of the beast. The most complete skeleton, from Egypt, was destroyed in 1944 when the Allies bombed a museum in Munich, Germany. In the past decade or so, new fossil discoveries have led to a slew of studies on Spinosaurus, triggering renewed interest in understanding its lifestyle, said Darla Zelenitsky, an assistant professor of paleontology at the University of Calgary, who was not involved in the study.

So, what about Spinosaurus negates the "Olympic swimmer" claim? The new analysis suggested its weird body shape, especially its tall sail, would have created a lot of drag in the water. "Our rough estimate shows it would [have needed] to be many meters under the water to reduce the drag effect," Holtz said. "But as Spinosaurus is known from estuarine [swampy] environments, it was feeding not just in huge Mississippi- or Amazon-like channels, but in water of all depths."

"Most larger pursuit predators — from Jurassic ichthyosaurs to tunas to dolphins and so on — have relatively stiff bodies and short necks, with the propulsion generated from a rather concentrated area of motion in the tail," Holtz said. But Spinosaurus didn't have a short neck or a stiff body. "In contrast, the body of Spinosaurus is more like less specialized swimmers. And the fact that isotopic evidence shows they were also feeding on land strongly supports them as having a more generalized lifestyle rather than one committed to a single primary mode of life," Holtz said.

Spinosaurus had a relatively long neck that was curved like a coat hanger. "It's got this weird neck ... for stabbing down," added study lead researcher David Hone, a senior lecturer of zoology at Queen Mary University of London. Plus, its nostrils were halfway up its snout, not on top of its snout like a crocodile's. "That makes sense if you hold your nose just under the surface [while hunting]," rather than spending all its time mostly submerged, Hone told Live Science.

Other anatomical clues hint that Spinosaurus was more like a stork than a leviathan — Hone detailed many on Twitter, including that propulsion from long tails, like that of Spinosaurus, usually helps with short bursts, not lengthy pursuits, Hone said. The 2020 Nature study also showed that Spinosaurus couldn't swim as efficiently as a crocodile, in part because it had fewer tail muscles than crocs.

"So what's next for Spinosaurus? Who knows?" Lindsay Zanno, head of paleontology at North Carolina Museum of Natural Sciences and associate research professor at North Carolina State University, who was not involved in the study, told Live Science in an email. "But if it were me, I'd look more closely at the internal structure of the skeleton." The microscopic structure of the bone could reveal whether it floated well, Zanno noted.

Meanwhile, the lead author of the 2020 study is standing by his interpretation that Spinosaurus was a specialized predator of aquatic prey. "Long story short, it doesn't really change anything for us — there is nothing in the paper we have not considered before," Nizar Ibrahim, a senior lecturer of paleontology at the University of Portsmouth in the United Kingdom, told Live Science in an email.

Laura is the managing editor at Live Science. She also runs the archaeology section and the Life's Little Mysteries series. Her work has appeared in The New York Times, Scholastic, Popular Science and Spectrum, a site on autism research. She has won multiple awards from the Society of Professional Journalists and the Washington Newspaper Publishers Association for her reporting at a weekly newspaper near Seattle. Laura holds a bachelor's degree in English literature and psychology from Washington University in St. Louis and a master's degree in science writing from NYU.

Debate heats up over swimming ability of bizarre-looking Spinosaurus

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