Both the Raiusuchians and the Dinosaurs independently evolved an erect gait (where the limbs are positioned directly below the body rather than splayed outwards), but their anatomical approaches to this condition differed.
劳氏鳄和恐龙各自独立地演化出了直立步态（四肢在身体正下方，而不是叉开向外），
但是他们实现直立的解剖学结构却并不相同。
Three bones make up the pelvis: the pubis,the ischium and the illium.
At the junction of these three bones, there is a socket into which the head of the femur fits called the acetabulum.
In Dinosaurs, the head of the femur is bent– that is, offset at an angle to the main body of the bone. The head fits into the acetabulum. The dinosaur acetabulum, rather than being a solid bone-pocket, actually has an opening in it (an open acetabulum is one of the defining features of the dinosaur clade).
The dinosaur femoral head is rather more barrel-shaped that the bulbous head of the human femur, limiting thigh motion to a plane parallel to the body.
骨盆由3块骨头组成：耻骨、坐骨和肠骨。
在这三块骨头的交界处，有一个放置股骨体的插座被称为髋臼。
在恐龙中，股骨的头部是弯曲的 —— 也就是说，向骨的主体部分发生了偏移。股骨头适合进入髋臼。恐龙的髋臼不是一个牢固的骨口袋，实际上有一个开口（开放的髋臼是恐龙类群的特征之一）。
恐龙的股骨头与人类圆形的股骨头不同，更像是桶装，以此限制大腿相对身体的平行移动。

不错

可

柱状直立有什么优缺点呢？为什么现金存活的生物都放弃了这条路线