Long before dinosaurs walked the Earth, sharks were in the oceans. Their legacy has been traced back at least 420 million years which is quite amazing. They have been able to evolve as needed in order to continue surviving. What is interesting though is that there hasn’t been that much evolution with them compared to many other types of animals on Earth and in the ocean.
It can be hard to find fossils of sharks though which has made some types of research quite difficult. The fact that their bodies consist of cartilage and not bones means there isn’t much remaining to be found. Bones can be well persevered for thousands and thousands of years.
However, cartilage has a very fast rate of decomposition. So how do researchers and scientists know that sharks existed millions of years ago? It is due to the many teeth that they have in their lifetime. Each shark can produce up to 30,000 teeth over the span of their life. These teeth consist of dentine and enamel which does fossilize in the ocean. There are ways to determine how old these teeth are. That has lead to significant evidence of how long sharks have been around.
Scientists have come up with some great photos of what they believe prehistoric sharks looked like. This is based on the formation of the jaws and the shape of the teeth found at the bottom of the ocean. They believe these changes too place due to the habitat, diet, the evolution of other aquatic live around them.
It is believed the biggest evolution of sharks took place during the Cretaceous period. During this time there was an abundance of food and the sharks were getting larger and larger with many species. At the same time the food sources were expanding where they were located.
Therefore the sharks no longer had to remain in one place. Many of them migrated to new areas of water in order to follow the food sources. As they found new environments though they had to evolve in order to be able to survive there. In some areas there weren’t very many fish or other meaty aquatic live forces to consume. It is believed this is when some species of sharks became more dependent upon other food items in the ocean including clams and mollusks.
Researchers have found some body indentations along with teeth that date back to the Miocene period. These indicate that some significant changes took place among the design of the sharks around that time. Their bodies developed to allow them to survive in the water by moving quickly and processing oxygen through their gills.
Another significant period of evolution for sharks is noted around 5 million years ago known as the Pliocene period. It is believed that the changes in this period of time were due to the changes in the temperatures of the water. Many species of sharks had to adapt to the colder waters. Their bodies were able to do so and so they continued to survive as the oldest living creature in the water. They are magnificent creatures who have continued to stand the test of time through all that has happened in the waters of the world.
From the findings of prehistoric sharks, researchers and scientists have been able to piece together their evolution. It is one that is very interesting and shows us the strength and adaptation skills of the sharks. There is a great deal to be learned from this particular aquatic creature. Sharks have placed a remarkable role in the evolution of other animals in the water as well.