There were bipeds, tripeds and quadrupeds.

有两、三和四。

And the situation is very different with other four-legged animals, tetrapods.

这种情况与其它四有非常大的不同。

The dog is the most knowing and clever of all four-footed animals.

四当中，狗是最善解人意、最聪明的。

The four-legged animal is believed to have been just 10 centimeters tall and about 40 centimeters long.

据信，这种四只有10厘米高，约40厘米长。

Today three early tetrapods are known and none has five digits.

今天，已经知道早期有三种四，但没有一种跟数字5有关系。

Whatcheeria was an early tetrapod, as the first land animals with backbones were known.

瓦切螈是一种早期的四，作为第一批有脊椎的陆地而为人所知。

Unlike many early tetrapods, bones of Whatcheeria have been discovered from different points in the animal's life.

与许多早期四不同的是，人们发现了瓦切螈不同生命阶段的骨骼。

Bears are quadrupeds, meaning they walk on four legs, but they are able to stand up on their hind legs.

是四，用四条腿走路，但他们也能用后脚站立。

Pachyrhinosaurus though was a more compact quadrupedal kind of animal, a more sturdy build than what we see in Albertosaurus.

肿鼻角龙是一种更结实的四，比阿尔伯特龙身体更加粗壮。

This was the missing link between bony fishes and tetrapods, including human beings, so this was a fantastic expectation.

这是硬骨鱼和包括人类在内的四之间缺失的一环，所以对我们来说这种期待很奇妙。

You never meet with quadrupeds going up and down walls; you must not have quadrupeds represented upon walls.

你永远不会遇到四在墙上上下移； 你不能在墙上展示四。

While animals that walk on four legs are called quadrupeds.

而四行走的被称为四。

What’s clear is that these tetrapods were walking on all fours, not paddling or flopping.

很明显，这些四是四行走，而不是划桨或翻滚。

Your few four-legged ancestors, the tetrapods, struggled in tropical river plains.

你的少数四祖先， 四，在热带河流平原上挣扎。

But the bigger news was a major change among the tetrapods.

但更大的消息是 四发生了重大变化。

And a new way of breathing wasn’t the only thing tetrapods would need.

一种新的呼吸方式并不是 四唯一需要的。

The object of the class was take a four legged animal, it can be any animal.

这的对象是一只四，它可以是任何。

A " deer" is a large, four-legged animal that eats grass and can run very quickly.

“鹿”是一种大型四，吃草而且跑得很快。

For it would appear that climate has some direct action on the hair of our domestic quadrupeds.

因为气候似乎对我们家养四的毛发有一些直接影响。

In particular they sought lobe-finned fish of the type that presumably were ancestral to us and all other walking creatures, known as tetrapods.

据推测，那种鱼是所谓的四，即我们和其他所有会行走的的祖先。