This animal is called horseshoe crab, which is an ancient marine arthropod.

In fact, hoofed crabs have a wide disk-shaped body and a slender needle-shaped tail. Although there are still five species of horseshoe crabs, they have been less common since the late Cretaceous.

horseshoe crab looks like shrimp and crab, but it is not a real crab, but a very primitive arthropod. It is a kind of animal as old as trilobites. Their ancestors can be traced back to the Cambrian period, but it was not until the Jurassic period (more than 1 million years ago) that the appearance of horseshoes was exhibited. Since then, until today, the shape of horseshoe crab has not changed.

horseshoe crab's blood contains copper ions, and its blood is blue.