by When did sharks first appear
Learn about the awesome history of sharks and how these creatures have been able to adapt and sᴜʀᴠɪᴠᴇ conditions that ᴋɪʟʟᴇᴅ off many prehistoric life forms. Their survival tactics were endless, from a prehistoric shark that had saw-like dentition to another one that can walk on land.
Let’s talk about the history of sharks.While often referred to as living fossils, sharks have evolved many different guises over the hundreds of millions of years that they have been swimming the oceans. Sharks belong to a group of creatures known as cartilaginous fishes, because most of their skeleton is made from cartilage rather than bone. The only part of their skeleton not made from this soft, flexible tissue is their teeth. The group includes the more famous animals such as whale sharks and great whites, but also all rays, skates and the little-known chimaeras. The earliest fossil evidence for sharks or their ancestors are a few scales dating to 450 million years ago, during the Late Ordovician Period.
450 million years ago, during the Silurian period, sharks first began developing as a unique species. During that time, the ocean was filled with a variety of bony fish. One of these fish, the Acanthodian, was the very first ancestor of the modern shark. Acanthodians, also called “spiny sharks,” were the first fish to not only take on the physical characteristics of a shark, but to develop the cartilaginous skeletal structures that define sharks. All sharks living today have evolved from this early fish.
About 50 millions years of after the SIlurian Era, the Devonian Era began. This is when the very first, fully developed shark, the Leonodus Shark, evolved. Very little is known about the leonodus shark. However, the fossil remains of its two-pronged teeth lead scientists to believe that it was about 16 inches long, with an eel-like body and lived in freshwater. Another freshwater shark discovered from this period was the Antarctilamna. The Antarctilamna was also eel-like but had a small fin behind it’s head. Both of these species are considered to be in the now ᴇxᴛɪɴᴄᴛ early shark genus Xenacanthus. Though new sharks are still being discovered, we know of about 500 species that exist to date.
