There were bipeds, tripeds and quadrupeds.

有两足、三足和四足动物。

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

这情况与其它四足动物有非常大的不同。

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

四足动物当中，狗是最善解人意、最聪明的动物。

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

据信，这四足动物只有10厘米高，约40厘米长。

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

今天，已经知道期有三四足动物，但没有跟数字5有。

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

瓦切螈是期的四足动物，作为第批有脊椎的陆地动物而为人所知。

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

与许多期四足动物不同的是，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.

熊是四足动物，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.

肿鼻角龙是更结实的四足动物，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足动物之间缺失的环，所以对我们来说这期待很奇妙。

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

你永远不会遇到四足动物在墙上上下移动； 你不能在墙上展示四足动物。

While animals that walk on four legs are called quadrupeds.

而四足行走的动物被称为四足动物。

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

很明显，这些四足动物是四足行走，而不是划桨或翻滚。

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

你的少数四足祖先， 四足动物，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 四足动物发生了重大变化。

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

新的呼吸方式并不是 四足动物唯需要的。

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

这堂课的对象是只四足动物，它可以是任何动物。

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

“鹿”是大型四足动物，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足动物的毛发有些直接影响。

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，那鱼是所谓的四足动物，即我们和其他所有会行走的动物的祖先。