Cambrian Period 540 Million Years Ago
540 Million Years Ago, nothing lives on land, but a different story exists under the oceans. Evolution has been pulsing slowly and steady for millions of years. The oceans are filled with simple, soft body organisms, blindly drifting away with the currents. In the shallow coasts however, evolution has slowly picked up the pace.
The Anomalocaris has been preying on smaller animals. Anomalocaris is the first super predator during this period. This 4 foot predator is a result of a slow evolutionary move. This animal possessed eye sight, its eyes were composed of many lenses. Other prey and predators possess sight. Being able to see and be seen by other enemies made the evolutionary process more challenging. To combat being visible and vulnerable, many organisms on these shallow seas have developed rigid exoskeletons to protect against the enemy. These armored organisms are called artrhopods. In the future they give rise to both, insects and spiders.
This is Haikouichthys, it is named after a place in China where its fossils were found. It is only the size of your thumb nail, but an evolutionary giant. Its the first species of fish. It is critical to our evolutionary line, because of instead of having armor on the outside, it is tough on the inside. It has a primitive back bone, a notochord which makes it the very fist vertebrate. He is the forth barer of all backbone animals, from dinosaurs, to elephants, to humans.
Although lacking fins, its flexible backbone makes it more flexible and maneuverable than the spineless Anomalocaris. While these tiny backbone ancestors may have survived among other predators, they must adapt or die out. As millions of years pass by, fish built on their basic design.
The muscles on their backbone evolved into a powerful tail, and fins began to sprout. They also developed a distinct head. These animals may not look like you and I but this fish became the blueprint to our bodies. This fish now evolved is called Cephalaspis. Cephalaspis would not appear until the Silurian Period about 480 million years ago.
The Cambrian Period saw a huge expansion of life. Many of these new animals would not survive beyond the end of the Cambrian Period, such as those that were first identified as fossils in the famous Burgess shale.
It is not clear why the Cambrian explosion did happen, but it is believed that it may have been triggered by changes in oxygen levels or in the layout of the seabed. Or that life may have reached a critical point, triggering off a chain reaction in which many new body types evolved.
Although Cambrian animals lived in the sea, few of them were creatures of open water. Instead, animal life dwell on the ocean's floor.