Ornithischian dinosaurs like Triceratops and Stegosaurs lack these air sacs and as a result, most of them weren't very big.

三角龙和剑龙属于鸟臀目恐龙，缺少这些气囊，因此它们大多数的体型并不大。

It's a closed relative of Triceratops, and the group called the ornithischians.

它是三角龙的近亲，属于鸟臀目恐龙。

Ouranosaurus has a spike-like thumb and a dental battery, and was an iguanadont ornithischian.

Ouranosaurus 有一个尖刺状的拇指和一个牙齿电池，并且是一种鬣蜥鸟臀目。

Well that’s where a major change occurred in ornithischian dinosaurs.

很好，这就是 鸟臀目恐龙发生重大变化的地方。

That makes it an Ornithischian dinosaur.

这使它成为鸟臀目恐龙。

This beak gave ornithischians a tool for slicing off plant stems.

这种喙为鸟臀目动物提供了切下植物茎干的工具。

Sometimes, the backwards pointing pubis on an ornithischian dinosaur.

有时，鸟臀目恐龙的耻骨向后指。

All the way over on the other side of the dinosaur family tree, there's another, broader group called the ornithischians.

在恐龙家族树的另一边，还有另一个更广泛的群体， 叫做鸟臀目。

And in the 1990s, researchers studied the nasal regions of three species of theropods and one ornithischian.

在 1990 年代，研究人员研究了三种兽脚类动物和一种鸟臀目动物的鼻部区域。

And all skulls have the predentary bone present in ornithischian dinosaurs.

所有的头骨都具有鸟臀目恐龙中的原始骨骼。