Water and air pose completely different challenges to animals on a number of levels.

The motivation behind everything that animals do is to stay alive, at least until they have produced offspring. Any species ...

Only animals that evolved to live solely on land ever developed claws. The earliest vertebrates -- fish and amphibians — never developed hard nails and remained dependent on watery environments ...

How Ancient Reptile Footprints Are Rewriting the History of When Animals Evolved to Live on Land WASHINGTON (AP) — Scientists in Australia have identified the oldest known fossil footprints of a ...

Only animals that evolved to live solely on land ever developed claws. The earliest vertebrates — fish and amphibians – never developed hard nails and remained dependent on watery environments ...

Only animals that evolved to live solely on land ever developed claws. The earliest vertebrates -- fish and amphibians – never developed hard nails and remained dependent on watery environments ...

Only animals that evolved to live solely on land ever developed claws. The earliest vertebrates -- fish and amphibians – never developed hard nails and remained dependent on watery environments ...

WASHINGTON (AP) — Scientists in Australia have identified the oldest known fossil footprints of a reptile-like animal, dated to around 350 million years ago.. The discovery suggests that after the ...

Only animals that evolved to live solely on land ever developed claws. The earliest vertebrates — fish and amphibians – never developed hard nails and remained dependent on watery environments ...

Only animals that evolved to live solely on land ever developed claws. The earliest vertebrates -- fish and amphibians – never developed hard nails and remained dependent on watery environments ...