central shaft meaning in English

中心轴

The feathers attached to the arms and the tail evidently possess the structures of " modern feathers " , which consisting of the central shafts ( rachis ) and parallel barbs . dromaeosaurids are unusual group of maniraptoran theropods . they share many similar or the same features with archaeopteryx or other primitive birds , such as : u - shaped furcula , uncinate process , laterally facing glenoid of shoulder girdle , comparatively long forelimb , large semilunate carple , retroverted pubis , ascending process of astragalus , and " modern feathers " with rachis and barbs etc . these facts indicate not only that dromaeosaurids had developed many bird - like characters in course of the advanced maniraptorans toward birds , but also that there seemed to be the co - evolutionary trend between the feathers and the skeletal bones
奔龙类是一类较为特殊的手盗龙类( maniraptora ) ，它具有许多与始祖鸟archaeopteryx甚至其它早期鸟类相似或接近的特征，主要表现在：叉骨u形与始祖鸟和孔子鸟类的相同，背肋钩状突在孔子鸟类和个别反鸟类中也存在，肩臼窝绝大部分指向侧方类似于始祖鸟，肩胛骨与乌喙骨间的夹角非常接近90也和始祖鸟的相似，前肢从比例上讲显得较长，大的半月形腕骨使肘部能向侧方折过来，耻骨伸向后下方，距骨上升突与原始鸟类中的为同源结构，羽毛已有显著的分化且具备了现代羽毛的基本结构等等。