"If I had a time machine, I'd go back a hundred million years to what is now Morocco's Sahara Desert," says paleontologist Nizar Ibrahim.

But time travel to the mid-Cretaceous period would be dangerous. At the time, the Sahara contained a lush river system teeming with life, with huge flying reptiles overhead, 40-foot crocodiles prowling the rivers, and predatory dinosaurs larger than Tyrannosaurus rex dominating the land. All were devouring massive turtles, fish—and each other.

"I call this 'river of giants' the most dangerous place on Earth, a true predator's paradise," says Ibrahim, a postdoctoral researcher at the University of Chicago. "You virtually never see such a high ratio of meat-eaters to plant-eaters."

It's the kind of place that could help paint a more vivid picture of dinosaur life and make paleontology more accessible to the general public—one of Ibrahim's chief goals. He sees learning about dinosaurs as a way for more children to develop a passion for science.

"Paleontology is like detective work," Ibrahim says. "It's amazing to piece together clues and re-create a hundred-million-year-old landscape where gigantic predators flourished and enormous evolutionary changes unfolded."

In his latest fossil findings, released Thursday by Science magazine, Ibrahim and colleagues reveal the most detailed look ever at the biggest and baddest of carnivorous dinosaurs—Spinosaurus.

Recovered from a local fossil collector, the fossil bones of Spinosaurus aegyptiacus turned up in sandstone beds in the Moroccan Sahara. The fossils reveal a crocodilian snout, paddle-like feet, and dense bones that aided buoyancy for the 50-foot-long (15.2-meter-long) dinosaur, adding up to a life aquatic for the giant predator.

Living most of its life afloat, Spinosaurus appears to have been the first dinosaur to take to the water. Rather than running on its two hind legs, the fossils show the largest predatory dinosaur—some nine feet (just under three meters) longer than T. rex—was heavily "front-loaded" and likely walked on all fours on land.

Armed with formidable front claws and a massive crocodilian skull, the creature lived off fish, and may have fought its biggest battles with the oversize sawfish, some as much as 25 feet (7.6 meters) long, whose fossils have turned up in the region as well. Other fish, ancient crocodiles, and even a small sauropod dinosaur roamed the river system where Spinosaurus made its home.

"We found an entire lost world—a window on a moment of major evolutionary change," Ibrahim says. "It's quite unique to discover animals from the water, land, and air coexisting in one such highly productive place and time."

Another of Ibrahim's recent discoveries: a new species of flying reptile that soared with a breathtaking 20-foot wingspan. An early ancestor of the largest flying creature ever, it is, to this day, the largest flying species ever to have been found in Africa.

Because the bones of flying animals are extremely light and fragile, few survive millions of years. Before his own forays, Ibrahim says that "all the bones of flying reptiles found in Africa could fit on a very small table."

By trekking to virgin desert never explored by other researchers, he unearthed beaks, jaws, and neck bones and assembled a collection of specimens that in 2010 revealed a new species of pterosaur he christened Alanqa saharica, phoenix of the desert.

For Ibrahim, fieldwork in hostile landscapes is challenging but essential. "The African continent remains a mystery in our big-picture analyses of large-scale animal evolution, diversification, and extinction," he says. "Only by finding and documenting fossils in the field can we understand their geological context and ancient ecosystems—and if that means going to remote parts of the Sahara, then that's what you've got to do."

His passion for paleontology bloomed early; Ibrahim's grandmother still has dinosaur drawings he made at age five.

"I grew up in West Berlin, and at that time the Natural History Museum was on the other side of the Berlin Wall, so my parents had to get special permits to take me there," he remembers. "It had the world's tallest mounted dinosaur skeleton, and I was awestruck.

"Years later I was asked to be a scientific adviser when the museum's dinosaur hall was redesigned—I got to help remount that same skeleton, which now strides majestically through the hall."

Today, Ibrahim feels like he's following in the footsteps of the early explorers who "gave us the first science-based descriptions of animals like the rhinoceros and hippopotamus."

Hair-raising adventures in far-flung lands are only part of the job. There are many long nights spent combing museum collections and countless hours of painstaking lab work. He identifies each of the thousands of bone fragments he finds and logs them into a database at the University of Casablanca.

But the work helps him retain a long-view perspective.

"It's easy to become focused on our little human world in this tiny slice of current time," he says. "I want us to step back and be amazed by millions and millions of years of evolution that happened before our species was even around."

That understanding, Ibrahim says, could spur today's humans to help protect the planet.

"Paleontology is really the only tool we have to understand that whole history and how major global changes affected it," he says. "Today, as we struggle with climate change and so many endangered species, I think it's more important than ever to treasure and protect the diversity that remains."