Huge and Aquatic—Meet Spinosaurus, the biggest predator of the Cretaceous period!period

Have you ever thought scientists might find a dinosaur bigger than Tyrannosaurus rex?

They have. Paleontologists—scientists who study fossils—have identified a dino which measured 50 feet. That’s 9  feet longer than any T. rex ever found. It was bigger than a bus. And what’s even more interesting, this big guy, Spinosaurus, lived and hunted in the water as well as on land. Before this discovery, paleontologists knew that some huge prehistoric reptiles, like crocodiles, lived in water.  But no aquatic dinosaurs had been identified before.  
    This was not really a new dinosaur.  About 100 years ago, in 1912, a bone and fossil collector,  Richard Markgraf, found some bones—parts of ribs, a lower jaw, tail and vertebrae which were attached to large, flat, long spines. Ernst Stromer, a German paleontologist, examined the bones and saw that these fossils were different from any other dinosaur bones found before that time. Because the bones were different, he knew he had a new dino. But what kind of dino? And what should he call it?
    The new dinosaur’s jaw was long and slender and had teeth good for catching fish. The scientist thought this new dinosaur was a gigantic predator that may have spent some time hunting in the rivers of North Africa. It probably fished by dipping its head in the shallows. The spines on the vertebrae that he found were likely to have formed a sail. Strommer called his new find, Spinosaurus. Because he had found it in Egypt, he called it Spinosaurus aegyptiacus.
    Back in 1915, Strommer had an idea of what Spinosaurus might have been like, but not a good idea. He didn’t have enough bones to picture the giant. That changed in 2013. Then Nizar Ibrahim, another paleontologist, found a very large number of Spinosaurus bones. It turned out to be a young dinosaur—not fully grown—but it was already 36 feet long. Scientists determined that a full grown Spinosaurus would have been about 50 feet long, the largest predatory dinosaur found so far. Even bigger than the fearsome Tyrannosaurus. They knew that it had lived about 97 million years ago, in Africa. In an area full of other big predators.
    How do paleontologists figure out what a bunch of bones might represent? It is like putting a puzzle together—being a detective and using clues. Putting the skeleton together is the puzzle part. They used bones they found from different Spinosaurs. They filled in missing parts by using what they know about other animals and dinosaurs.
    They figured out how the dinosaur lived by comparing the bones to other animals’ bones. Spinosaurus bones were dense—thick and heavy— and compact, like the bones of penguins and whales—animals that spend most or all of their time in the water.  The dense and compact bones help them stay in the water. The bones that formed the dinosaurs hips, were like the bones of other animals that had moved from land to water. The nostrils on its head were set back, closer to the eyes on the snout. This would have allowed Spinosaurus to breathe while keeping its head mostly under water—like crocs.
    Have you ever seen a crocodile’s teeth? They are different from most animal’s teeth. They are conical and interlock. Guess what? Spinosaurus’ teeth are conical and interlock too. From this clue, paleontologists could tell that Spinosaurus would have eaten the same thing that  some crocodiles eat—fish—huge fish. Another clue that they preyed on fish is the pits found on the jaw bones. The pits are holes that may have allowed the animal to know of movement of prey under water.    
    The new dino’s forelimbs had foot-long claws to tear meat. The arms were strong and large and the back legs were short, with paddle-like feet—both good for swimming. And more importantly, a dinosaur that large, with such small back legs, would not have been very good on land. It would have been slow. It would not have been able to stand on its back legs for long periods of time like T. rex. Instead, it probably walked on all fours—rather slow—while on land. A long and flexible tail, like a crocodiles’, might have helped push Spinosaurus through the water.    
    And what about the spines that give Spinosaurus its name? Scientists think the spines formed a sail. Maybe it allowed other dinos to see it while it was partially under water.
    Now that you know the clues scientists used, can you see how the paleontologists think that Spinosaurus was the first semi aquatic dinosaur found? Do you like to solve puzzles? Maybe you would enjoy being a paleontologist. Check out the links below to see more pictures of the scary beast.  If you live in the Washington, D.C. area, you can see a life-size model of the frightening Spinosaurus, the largest and the first aquatic dinosaur found. It’s on display outside the National Geographic Museum.     

Here are the articles I read to write this blog post. You can find a really cool story about how the bones were found if you read some of these. Nizar Ibrahim, Ph.D., the paleontologist and National Geographic Explorer who analyzed the newest Spinosaurus bones, was unbelievably helpful to me in writing this blog. Clare Jones, also from National Geographic, helped me obtain the pictures you see here.  Thank you to National Geographic for the use of these beautiful pictures.

Changspet, Kenneth. “A Lost-and-Found Nomad Helps Solve the Mystery of a Swimming Dinosaur.” http://www.nytimes.com/2014/09/12/science/a-nomads-find-helps-solve-the-mystery-of-the-spinosaurus.html?_r=0 Accessed September 17, 2014.

Joyce, Christopher. “Crocodile Meets Godzilla—A Swimming Dino bigger than T. Rex.” http://www.npr.org/2014/09/11/347488364/crocodile-meets-godzilla-a-swimming-dino-bigger-than-t-rex. Accessed September 17, 2014.

Mueller, Tom. “Mr. Big.” http://ngm.nationalgeographic.com/2014/10/spinosaurus/mueller-text. Accessed September 17, 2014.

Switek, Brian. “What Do We Know About Spinosaurs?” http://www.smithsonianmag.com/science-nature/what-do-we-know-about-spinosaurs-89178721/. Accessed September 18, 2014.

Thompson, Helen. “First Dinosaur Adapted for Swimming.” http://www.smithsonianmag.com/science-nature/meet-mighty-spinosaurus-first-swimming-dinosaur-180952679/?utm_source=smithsoniansciandnat&no-ist Accessed September 17, 2014.

Watson, Tracy. “New ‘Massive’ Dinosaur Skeleton Discovered.” http://www.usatoday.com/story/news/nation/2014/09/11/dinosaur-swimming-spinosaurus-skeleton/15448103/. Accessed on September 17, 2014.