Imprints of mollusk shells are sometimes found on stones. Rock formations contain imprints of ancient plants and unicellular organisms, very different from their modern counterparts.
The first living creatures living in the water had no head, no legs, no mouth. These were small masses of living matter.
Sponge
After quite a lot of time after the appearance of the first living creatures in the sea, living creatures began to develop, arising from colonial forms. These were the first multicellular animals — sponges. Two billion years have passed since then, and the sponges have not changed.
Also appeared:
- jellyfish
- trilobites
- flatworms
- oncophors
- sponges
- multi-bristle worms
- sea lilies
- ancient corals
- nautilus
- sea stars
- scorpions
- horseshoe crabs
- ammonites
At the bottom of the sea
400 million years ago, different types of algae lived on the bottom of the sea, since plants at that time could only live in water. On the ground, protruding above the surface of the water, not a single blade of grass has yet grown.
Curtailed house
Several thousand years passed, and nautiluses appeared in the seas - mollusks with a shell twisted into a spiral. It was their "home." In those days, ammonites were very numerous - extinct animals with this type of shell. And nautiluses swim in the seas to this day.
First fish
At that time, the first vertebrate animals — fish — had already appeared. They were very different from modern fish: they had a fixed, always open mouth, with which they drove along the bottom silt in search of food.
