Who was the first marine animal?
Dylan (five years old), asks: Who was the first marine animal?
Hannah from Planet Tuna answers: The first marine animals appeared about 560 million years ago, in a geological period called the Ediacaran. As you can see from the picture, these first animals were very odd. Some stayed in one place like a plant and probably filtered nutrients from the water around them. Others could move slowly along the sea bottom. They could afford to be soft-bodied and slow because there were no predators yet. Some of the best-known are Dickinsonia, which looks a bit like a pancake, Arborea, which looks like an upright leaf, and Spriggina, which was one of the ones that could move about.
In the following period, the Cambrian, we see the first predators, as well as many new types of animals with defenses against being eaten such as hard shells, spines, pincers, or the ability to swim away fast. The defenseless Ediacaran animals all disappeared.
The first marine animals were also the first animals on the entire planet, because life on dry land took a while to evolve, and the first land animals didn’t appear until much later, in the Silurian period.