Dinosaurs were a diverse bunch of animals. There were herbivores and carnivores, long-necks and crested heads and horned giants. Some, maybe most, were feathered and some may have been warm-blooded, unlike the reptiles of today. Some even lived on after the asteroid collision that ended their dominance over the planet - you can see their modern descendants flying around you!
But one thing we've always understood about dinosaurs is that they were all, whether big or small, whether predator or prey, land animals.
No more. Read on for today's big news from the world of paleontology.
You remember Spinosaurus, right? That's the huge, sail-backed dino that took on the T-rex in the third Jurassic Park film. Well, it was not that great of a movie and it didn't help that there is no chance a Spinosaurus ever would have met up with a Tyrannosaurus rex. They lived on different continents!
But the cinematic portrayal of Spinosaurus as a huge animal was dead-on. Way back in 1915, the German paleontologist Ernst Stromer von Reichenbach described some remains of the animal that had been found a few years earlier in Egypt's western desert. He named the beast Spinosaurus aegyptiacus for the huge spines that rose from its vertebral column.
Scientists as far back as 1926 considered Spinosaurus aegypticus as a very long animal - about 50 feet in length - and a debate over its size continued for decades. Paleontologists long presumed that Spino was a pescetarian. It has a similar skull to its cousins, Baryonix walkeri and Suchomimus terenensis, which were sort of heron-like in their behavior, dipping their feet in the water when they wanted a fishy treat.
Unfortunately, these questions could not be definitively resolved easily because, until now, there have been only a few fragments of the dinosaur available to examine. Stromer's fossils had been destroyed in a German museum when it was bombed by the Royal Air Force during World War II.
In today's Science Express paper, Nizar Ibrahim and Paul C. Sereno of the University of Chicago remove all doubt about Spinosaurus' length. But they also highlight something even more amazing: the animal spent most of its time in the water.
In 2008 Ibrahim stumbled across a bone in a little town in Morocco. Later, he realized it was similar to bones he had seen in the basement at a museum in Milan, Italy. One thing led to another, and over time Ibrahim and his colleagues pieced together a nearly complete individual of Stromer's "spine lizard."
In doing so, they found quite a few adaptations that make sense only if the animal was semi-aquatic, including a nose near the top of the skull (allowing it to keep its snout under the water), short hips and legs, flat and wide feet with bony extensions that likely supported paddle-like structures, very dense bones for buoyancy, and pressure regulators at the front of the skull.
Spinosaurus aegyptiacus did not spend all of its time in the water, of course. Like all dinosaurs, it laid eggs on land.
Like today's lions, jaguars, and cheetahs, it's possible that Spino and other predators might have encountered each other. The fossils don't tell us what might have happened if they did. But while a Charcharodontasaur had slashing teeth, Spino's long snout might have been a tough match for it.
Oh, yeah, that big sail on Spino's back: it was a display tool.
The reality that not all dinosaurs were land animals is amazing enough. What's equally wonderful about this discovery is the way in which it further illustrates the workings of evolution in the hot and wet environs of Mesozoic Africa and in the long reign of the dinosaurs. The rivers and swamps of Mesozoic Africa were an environmental opportunity for a predator, and Spino evolved from earlier theropods to take advantage of it.
It's a cool story for the dinosaur lover in your life and, if you are in Washington, D.C. there's an exhibition on Spino that opens tomorrow.
By the way, the fossils that led to Ibrahim's and Sereno's discovery, which were found in the Kem-Kem fossil beds of Morocco, will be returned to that country from their present locale at the University of Chicago.
If you're interested, you can read my Science for the Future piece on this news here.