[求助]问

Until a few centuries ago,any large bones discovered in the fields or caves of Europe,now known to be large prehistoric animals,were usually assumed to be
        the remains of giants and were often displayed as curiosities in castles,palaces town halls,churches ,and monasteries.

A.now known to be large prehistoric animals,were usually assumed to be
        

B.bones now known to be those of large prehistoric animals,were usually assumed to be

为什么要加bones呢？

这里的known to be 能换成known as 么？两者之间有什么区别么？

谢谢指点！！

加bones是为避免歧义

严格的说be known to be不是一句型，be known to是，意思是为......所知 这里不是在考be known构成的句型。

be known for 因为......而闻名

be known as 作为......而闻名