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Cattle and zebra share a meal in a pasture in Kenya. Ryan Lee Sensenig/Science hide caption

itoggle caption Ryan Lee Sensenig/Science

The Quay Brothers, filming Through The Weeping Glass at the Mutter Museum in Philadelphia. The Quays started filming without a script or a storyline. Edward Waisnis/Behind the Scenes with the Quay Brothers hide caption

itoggle caption Edward Waisnis/Behind the Scenes with the Quay Brothers

When the T. rex skeleton was first put on display, it was presented standing vertically, in this Godzilla-like pose, as seen at the Carnegie Museum of Natural History around 1950. Recent studies show the dinosaur actually kept its body horizontal. Watch the videos here to see how T. rex walked. Carnegie Museum of Natural History hide caption

itoggle caption Carnegie Museum of Natural History

The fossil of Australopithecus sediba could be the long-sought transition between ape-like ancestors and the first humans. "It shows a small brain, but a brain that's beginning to reorganize in some ways that resemble our brain," says anthropologist Lee Berger. Brett Eloff via Lee Berger/University of Witwatersrand hide caption

itoggle caption Brett Eloff via Lee Berger/University of Witwatersrand

An artist's reconstruction of the Tibetan woolly rhino. Woolly rhinos used their flattened horns to sweep snow off of vegetation, a critical adaptation to survive frigid conditions. Image by Julie Naylor hide caption

itoggle caption Image by Julie Naylor

Two women check their cellphones as they hawk their wares on a bridge over the Artibonite River, whose waters are believed to be the source of Haiti's 2010 cholera outbreak. Nicholas Kamm/AFP/Getty Images hide caption

itoggle caption Nicholas Kamm/AFP/Getty Images

A Libyan oil worker at a refinery inside the Brega oil complex, in eastern Libya, on Feb. 26. Production at Brega has dropped by almost 90 percent amid the country's crisis because many employees have fled, and few ships are coming to the port. Hussein Malla/AP hide caption

itoggle caption Hussein Malla/AP

Workers move a section of well casing into place at a natural gas drilling rig near Burlington, Pa. The industry is expected to drill as many as 10,000 new wells in the next few years. Ralph Wilson/AP hide caption

itoggle caption Ralph Wilson/AP

Last year, the Obama administration canceled plans to make Yucca Mountain the permanent storage site for the nation's nuclear waste. The half-built site is seen here in a file photo from 2006. Isaac Breekken/AP hide caption

itoggle caption Isaac Breekken/AP

The U.S. Nuclear Regulatory Commission says American nuclear plants need to be better prepared for the sudden and continued loss of electric power. Above, the Limerick Generating Station, a nuclear power plant in Pottstown, Pa. Stan Honda/AFP/Getty Images hide caption

itoggle caption Stan Honda/AFP/Getty Images