The sands of the Sahara Desert have delivered a new and very strange dinosaur: an elephant-size beast whose skull and jaw are unlike anything scientists have ever seen. They are calling it the "Mesozoic Cow."
Paleontologist Paul Sereno, who discovered the bones, has a reputation for finding new kinds of dinosaurs in out-of-the-way places. This find was unearthed in Niger, where it had been buried under the sand since the Mesozoic era, 110 million years ago. Sereno spent years piecing together the creature's bones. When he got the head and jaw together, he was shocked.
"Well the first thing that comes to my mind is that this is the weirdest dinosaur I've ever seen," he says. "It's some kind of Darth Vader dinosaur when you look at the skull. You put the skin on it and ... most people think it looks like a vacuum."
The "skin" is a plastic rendering of what the animal, called Nigersaurus taqueti, looked like. Sereno calls Nigersaurus an "extreme dinosaur" — one of nature's more bizarre experiments.
"It has jaws wider than the skull," Sereno says. "There's no other animal that's done that. All the teeth [are] up front in some type of conveyer belt fashion to create these shears," says Sereno.
The shearing teeth are aligned across the front of the wide, boxy mouth like a row of sharpened piano keys. Sereno says the animal probably used the top and bottom rows like scissors to graze on low-growing ferns or primitive plants, like horsetail. Its mouth held as many as five replacements for each tooth at any one time and probably lost a row every month.
The scientists also discovered something unusual by doing computerized tomography of its skull; CT scans are like three-dimensional X-rays. The scans revealed the bony remains of the animal's "organs of equilibrium" — like the semicircular canals in our own ears that help us keep our balance. From the positioning of those organs, it looks as though the animal spent most of its time with its head pointed almost straight down. That's different from the way the big long-necked dinosaurs are usually depicted. Combined with the mower-like teeth, it reinforces the idea of a ground-level grazer.
Paleontologist Larry Witmer of Ohio University says the scientists couldn't have figured that out without CT scanning.
"What it's done for paleontology is opened up really whole new vistas for questions we can ask about dinosaurs. Things we never even thought we could ask, we can now even answer," Witmer says.
Nigersaurus has more surprises, which Sereno points out as he gives a tour of its long, bony spine.
"The animal is about 30 feet long, and we are standing at the base of the neck that rises above our heads, and when you see the vertebrae in front of us, there's more air in each one of these vertebrae in the neck and in the back than there is bone," Sereno says.
In fact, many of the bones that make up the skull and jaw are remarkably thin and light. Sereno says he doesn't quite know what to make of that on such a big animal. It certainly wouldn't work on a mammal.
"Every mammal that has gone into serious chewing like a cow has made the skull more robust, they've enhanced the jaw muscles. This is breaking a lot of rules," he says. "I'm serving notice to the scientific community, to the biomechanics out there, you gotta explain this one."
The fossil remains of Nigersaurus are on display at the National Geographic Society in Washington, D.C., where Sereno is an explorer in residence when he's not teaching at the University of Chicago. Sereno describes the dinosaur in the latest issue of the online journal of the Public Library of Science.