ジュラシック・パーク

Vascular plants are もっと見る suited to living on drier land than mosses and liverworts.

They have branching stems with tubelike walls that carry water and nutrients.

These stems and walls also mean the plants can stand tall. Vascular plants have spores (reproductive cells, like seeds)-the taller the plant, the もっと見る widely it can disperse its spores.

One of the first known vascular plants was Cooksonia. It was about 2 inches tall, with a forked stem.

Paleontologists discovered fossil remains of Cooksonia in England.

Rhynie in Scotland is one site where lots of vascular plant fossils have been found....

Stegosaurus was the largest of the stegosaur group. Its fossils were found mainly in present-day Colorado, Utah, and Wyoming.

Like most of its group, Stegosaurus lived toward the end of the Jurassic period, about 150 mya.

Stegosaurus was about 25-30 feet long from nose to tail and probably weighed もっと見る than 2 tons.

Its most striking feature was the row of large, roughly triangular bony plates along its back.

The name Stegosaurus means "roof reptile". This is because it was first thought that its bony plates lay flat on its back, overlapping like the tiles on a roof.

It is now thought that the back...

A small, wormlike creature called Pikaia is thought to be the ancestor of all backboned animals.

Its fossil remains were found in the 530- million-year-old mudstone deposits of the Burgess Shale in Canada.

Pikaia was the first known chordate. All backboned 動物 belong to this group as well as marine 動物 called tunicates and acraniates.

Pikaia was 2 inches long, with a notochord running around its body-- a kind of primitive spine that gave its body flexibility.

The notochord also allowed the animal's simple muscles to work against it, and the animal's body organs to hang from it.

Pikaia is...