Category Archives: Early Vertebrates

What Are Vertebrates?

A donkey, a crocodile, a fish, a parrot, and a frog all have one thing in common. They all have a backbone, or vertebral column, connected to a supporting bony skeleton inside their bodies. They are all vertebrates. FA/MILY TREE OF VERTEBRATES Although vertebrates are the animals we know most about, they actually make up… Read More »

Jawless Fish

The first vertebrates were fish, but they were very different from today’s fish. The early fish couldn’t bite, since jaws were yet to evolve. Instead, they fed by sucking or scraping. With few or no fins, they swam by waggling their tails like tadpoles. They had no internal bones, but some had wide, bony shields… Read More »

Armored Fish

Also known as placoderms, the armored fish were the first fish to grow to a monstrous size, some reaching the size of modern sharks. They were also among the first fish with biting jaws, which they used as lethal weapons. For protection from each other, these prehistoric fish evolved suits of armor made of overlapping… Read More »

Sharks and Rays

Fossil teeth reveal that killer sharks have been cruising the seas for more than 400 million years—an astonishing length of time. Along with their flat-bodied relatives the rays, sharks belong to a truly ancient class of animals known as cartilaginous fish. These fish have no bones; instead, the skeleton is made of a rubbery material… Read More »

Megatooth Shark

The megatooth shark may have been the most terrifying and ferocious predator of all time—and possibly the biggest. This gigantic beast was a close cousin of today’s great white shark but was far larger: the height of its tail fin alone was equal to the length of a great white. The megatooth terrorized the seas… Read More »

Bony Fish

About 400 million years ago, a new family of fish began swimming in the seas. Unlike the sharks that had ruled the waters for millions of years, the new fish had skeletons hardened with calcium to form bone, earning them the name “bony fish.” The bony fish evolved into a huge range of new species… Read More »


This bony fish appears to have been a food choice of a ferocious dinosaur called Baryonyx, as a number of Lepidotes scales and bones have been found in the fossilized stomach area of this dinosaur. It was quite big itself, reaching lengths of up to 6 ft (1.8 m), and it was widespread— fossil remains… Read More »


During the Jurassic and Cretaceous periods, when dinosaurs ruled the land, the oceans were ruled by gigantic carnivorous reptiles called plesiosaurs. There were two main types: long-necked plesiosaurs, which had long, snakelike necks and small, dainty heads; and short-necked plesiosaurs (pliosaurs), which had huge heads and enormous, fang-filled jaws. FAMILY FACT FILE Key features ■… Read More »

Conquering Land

We know that land animals today evolved from creatures that lived in water millions of years ago. To move onto land, certain barriers had to be overcome—after all, a fin or flipper is not much use on land. Let’s take a look at some of the changes that took place. PROTEROGYRINUS FROM FINS TO LEGS… Read More »


Amphibians are animals that spend their lives partly in water and partly on land. They evolved from fish about 370 million years ago as fins slowly turned into fully formed legs that allowed them to walk on land. Amphibians were the first four-legged animals (“tetrapods”) and the ancestors of all four-legged animals alive today, from… Read More »