(BBC News) American scientists have discovered a fossil of a duck-sized，flightless dinosaur，which was apparently covered in feathers.

(英国国家广播公司报道)美国科学家发现了一个鸭子大小的化石，那是一只无法飞行的恐龙，身上很明显布满了羽毛。

The team believes that this prowes that feathers were developed for insulation，not flight.

研究小组相信，这证明动物长出羽毛的进化目的是保温，而不是飞行。

The scientists believe it means that modern-day birds are actually living dinosaurs.

科学家相信，这表示当今的鸟类其实是活恐龙。

The fossil is believed to be of a dromaeosaur.

据信这件化石是一只奔龙。

It could mean experts have to rewrite natural history books.

这可能意味着专家必须改写自然历史书了。