New Fossils Prove Spinosaurus Was an Underwater Terror

Credit: Kumiko https://www.flickr.com/photos/kmkmks/27388394090/ CC BY-SA 2.0

We’re all familiar with Tyrannosaurus Rex, a massive theropod dinosaur from the Cretaceous period and star of several movies about dinosaurs eating people. However, there were even larger, potentially more terrifying beasts on Earth all those millions of years ago. Spinosaurus was even bigger than the T-rex, and new discoveries indicate you wouldn’t have been safe even in the water. Spinosaurus, it turns out, was an excellent swimmer thanks to its large, paddle-like tail. 

Spinosaurus was a theropod like the Tyrannosaurus — that just means it had hollow bones and three-toed limbs. The descendants of theropods most likely evolved into modern birds, but Spinosaurus was more dangerous than any bird. Adults could weigh as much as 7.5 tons and grow to more than 50 feet in length, making them among the largest theropod dinosaurs. 

Researchers first proposed that Spinosaurus was primarily an underwater predator several years ago, but the scientific community was unconvinced. Donald Henderson, a paleontologist at Canada’s Royal Tyrrell Museum, noted that Spinosaurus was probably top-heavy with its distinctive back sail and would not have been able to dive underwater. Nazir Ibrahim, lead author of the study, believed the answer would be found in fossils. Previous excavations had only uncovered a few Spinosaurus tail sections, but the team uncovered an almost full set of tail bones at a fossil site in Morocco between 2017 and 2018. 

The newly reconstructed Spinosaurus was undeniably at home in the water. Rather than having a tapered whip-like tail, Spinosaurus had a giant fin attached to its backside. Some of the fossil bones were 12-inches thick, indicating the tail would have been a powerful mode of underwater propulsion. The team speculates Spinosaurus might have spent most of its time in the water. 

The team created a computer model to assess the capabilities of Spinosaurus’ tail, comparing it with modern land-dwelling dinosaurs and semi-aquatic creatures like crocodiles. Unsurprisingly, the Spinosaurus tail fin was about 2.6 times more efficient in the water than the tails of other theropods. 

Museums around the world will have to update their Spinosaurus models in the wake of this discovery, but that’s nothing new. The fossil record is incomplete, and sometimes we get details wrong when trying to reconstruct an entire animal from partial remains. The Tyrannosaurus Rex skeleton at the American Museum of Natural History in New York stood in the incorrect upright posture until 1992 before adopting the correct parallel position. Oh, the developers of Animal Crossing will have to update their inaccurate Spinosaurus fossils, too.

Top image credit: Kumiko/Flickr/CC BY-SA 2.0

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