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

情况与其它物有非常大的不同。

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

瓦切螈是一早期的物，作为第一批有脊椎的陆地物而为人所知。

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

今天，已经知道早期有三物，但没有一跟数字5有关系。

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

物当中，狗是最善解人意、最聪明的物。

There were bipeds, tripeds and quadrupeds.

有两、三和物。

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

据信，物只有10厘米高，约40厘米长。

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

是硬骨鱼和包括人类在内的物之间缺失的一环，所以对我们来期待很奇妙。

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

与许多早期物不同的是，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.

熊是物，用条腿走路，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.

肿鼻角龙是一更结实的物，比阿尔伯特龙身体更加粗壮。

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

你的少数祖先， 物，在热带河流平原上挣扎。

I’m using “cow” to mean “four-legged farm animal that moos”.

我用“牛” 来表示“会哞叫的农场物” 。

But it also had tetrapod like legs.

但它也拥有类似物的腿。

It was a term of derision for two-legged as well as four-legged animals.

它是对两物和物的蔑称。

And he came up with one called The Four-Legged Zoo.

他构思出了一个名为《物园》的节目。

But, the earliest tetrapods were all carnivorous predators.

但是，最早的物都是肉食性 捕食者。

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

但更大的消息是 物发生了重大变化。

These arid wastelands would’ve been uninhabitable for early tetrapods, but not for the amniotes.

些干旱的荒地 对于早期的物来是不适宜居住的，但对于羊膜物来却不是。

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

很明显，些物是行走，而不是划桨或翻滚。

One of the earliest of these new creatures was a tetrapod named Acanthostega.

些新生物中最早的一 是一名为棘螈的物。