Extinct headbutting relative reveals how the giraffe grew a long neck

This illustration compares the headbutting of an extinct giraffoid called Discokeryx xiezhi (foreground) with the neck-fighting style of modern giraffes (background).

(CNN)A strange early relative of the giraffe was perfectly adapted for some serious headbutting 17 million years ago, according to new research.

The oddball giraffoid didn't have the signature long neck of today's giraffe. Instead, the ancient animal, built for fierce fighting, sported helmet-like headgear and the most complex head-neck joints ever seen in a mammal.
Researchers have dubbed this creature Discokeryx xiezhi. In Chinese legends, xiezhi is a mythical one-horned creature resembling a goat.
    The fossil was first found in China's northwestern Junggar Basin in 1996, and researchers have been studying it at the Chinese Academy of Sciences' Institute of Vertebrate Paleontology and Paleoanthropology in Beijing ever since. Since then, more fossils have been recovered.
      At first, scientists weren't really sure what they were looking at as they studied the unusual skull and four cervical vertebrae. It was only within the last three years that researchers realized this weird fossil belonged to a giraffoid -- and that it might help them unlock how giraffes have evolved.

      Evolution of an oddball

      Since the time of Charles Darwin, scientists have tried to understand why the giraffe, the tallest land mammal, evolved such a long neck. Many researchers believed it was so the animal could reach tall foliage. As they studied giraffe behavior, they realized the long neck serves another purpose. When male giraffes compete for courtship with females, they use it to fight with one another.
        The muscled necks, which can be 6.5 to 9.8 feet (about 2 to 3 meters) long, can be used to smash their heavy skulls, armed with skin-covered bony protrusions called ossicones, against the weakest parts of a rival's neck. In short, the longer the neck, the greater the chance of inflicting serious damage.
        As researchers studied Discokeryx xiezhi, they began to fill in the missing pieces of giraffe evolution, including the evolution of a long neck, fighting behaviors and environmental pressure to reach vegetation.
        The male giraffe with the longest neck is at the top of the social hierarchy, and its need to compete for females is the driving force behind why its neck evolved to be so long.
        A study detailing the findings published Thursday in the journal Science.
        "Both living giraffes and Discokeryx xiezhi belong to the Giraffoidea, a superfamily. Although their skull and neck morphologies differ greatly, both are associated with male courtship struggles and both have evolved in an extreme direction," said study author Shiqi Wang, an associate professor at the Chinese Academy of Sciences' Institute of Vertebrate Paleontology and Paleoanthropology.

        Built for headbanging

        Discokeryx xiezhi had a heavily built cranium, or the thick bones that surround the brain. The roof of its skull was more than an inch (2.5 centimeters) thick, which was incredibly hefty for an animal about the size of a sheep, said study coauthor Jin Meng, curator-in-charge for fossil mammals at the American Museum of Natural History.
        This skull roof also had a large, flat surface where it grew a single, large disklike horn for headbutting.
        And the animal had a thick skull base and neck bones that were specialized to absorb extreme impacts, the researchers realize