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

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，并且一种鬣蜥鸟臀目。

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

很好，这就 鸟臀目恐龙发重大变化的地方。

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。

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.

所有的头骨都有鸟臀目恐龙中的原始骨骼。

There are two key traits that distinguish all ornithischians from thischians.

有两个关键特征可将所有鸟臀目与蓟亚目区分开来。

That's one of the easiest ways to tell an Ornithischian dinosaur from a Saurischian dinosaur.

这区分鸟臀目恐龙和蜥臀目恐龙的最简单方法之一。

To explore this concept further, let's take a look at some ceratopsians, a major group of ornithischian dinosaurs.

为了进一步探索这个概念，让我们来看看一些龙类，这鸟臀目恐龙的一个主要类群。

These species represented the earliest members of the Sertian Theropods and sauropods as well as primitive Ornithischian dinosaurs.

这些物种代表了塞尔提亚兽脚亚目和蜥脚类恐龙以及原始鸟臀目恐龙的最早成员。

First, ornithischians have a hip with a pubic bone that points backwards.

首先，鸟臀目动物的臀部有一个向后指向的耻骨。

They are a diverse group of plant-eating ornithischian dinosaurs that includes animals from the little Dryosaurus to the much larger Edmontosaurus and Iguanodon.

它们多种多样的以植物为食的鸟臀目恐龙，包括从小型龙龙到体型更大的埃德蒙顿龙和禽龙的动物。

Birds belong among saurischian dinosaurs, not among the ornithischians.

鸟类属于蜥臀目恐龙，而不属于鸟臀目。

The second trait that distinguishes ornithischians is a special bone in the lower jaw, called the predentary.

区分鸟臀目动物的第二个特征下颌有一块特殊的骨头，称为前齿骨。

The ankylosaur and ceratopsian don't have the broad beak of the hadrosaurs, so we'll draw a circle around the hadrosaurs and leave the other ornithischians out.

甲龙和龙没有鸭嘴龙的宽喙，所以我们将围绕鸭嘴龙画一个圆圈，将其他鸟臀目动物排除在外。

In other words, every dinosaur inside the circle is an ornithischian or bird-hipped dinosaur as we learned back in the first module of this course.

换句话说，正如我们在本课程的第一个模块中学到的那样，圆圈内的每只恐龙都鸟臀目或鸟臀恐龙。