Since the days of Charles Darwin, the long necks of giraffes have been a textbook example of evolution. The theory goes that as giraffe ancestors competed for food, those with longer necks were able to reach higher leaves, getting a leg-up or neck-up over shorter animals.

But a very unusual prehistoric giraffe relative reveals that, in addition to finding food, fighting may have driven early neck evolution. In a study published Thursday in Science, a team of paleontologists described the Discokeryx(獬豸盘角鹿), a giraffe ancestor, as having a helmet-like head and large neck vertebrae(脊椎).The Discokeryx evolved like this to absorb and deliver skull-cracking collisions to seek mates and defeat competitors.

“It shows that giraffe evolution is not just lengthening the neck,” said Jin Meng,a paleontologist at the American Museum of Natural History and co-author of the new study.

Head-butting is an ancient and widespread form of conflict solution. Dinosaurs like Pachycephalosaurs have firm skulls(头骨), and knocking heads remain common in bighorn sheep, chameleons and even whales.

But the researchers suggested that the Discokeryx was uniquely expert at head-to-head fight. The team estimated that collisions between Discokeryxes were likely twice as forceful as head-butting muskoxen, which strike each other at nearly 25 mph.

The series of interlocking neck joints haven’t been discovered in any other vertebrate(脊椎动物),living or dead,giving the Discokeryx the greatest head-bashing equipment yet discovered, according to the researchers. “This animal is an extreme example of using head-butting as a fighting tool,” Meng said.

【小题1】What do we know about the Discokeryx?

A．Its evolution helps make and bear crashes.

B．It has tiny neck vertebrae.

C．Its thin neck can stretch to find mates.

D．It has a horn-like head.

【小题2】What does the research find?

A．Whales move at the speed of 25 mph.

B．Muskoxen are good at giving a side attack.

C．Many vertebrates have amazing neck joints.

D．Discokeryxes hit opponents with big power.

【小题3】What is the text mainly about?

A．How Jin Meng completed a research paper.

B．Why giraffes’ necks evolve so long.

C．How the impact force between Discokeryxes is measured.

D．Why giraffes’ development goes against Charles Darwin’s theory.

【小题4】Where can the text be found?

A．In a:history book.

B．In a story collection.

C．In a science magazine.

D．In a celebrity biography.