Read more: These 12 Prehistoric Sea Animals Are Pure Nightmare Fuel Though arthropods are ubiquitous in the modern world, ...

Around 400 million years ago, Earth’s oceans were dominated by massive sea scorpions. Scorpions, as we know them today, are ...

Since the 1970s, populations of arthropods—a group of animals that includes exoskeleton-bearing critters such as insects, spiders, centipedes, and millipedes—in the Puerto Rican rainforest have ...

They’re also one of the world’s largest arthropods, animals with no backbone, external skeletons, and multiple-jointed appendages. In this crab’s case, those appendages are its 10 legs.

For over a century, the Cambrian arthropod Helmetia expansa remained a mystery. Discovered by paleontologist Charles Doolittle Walcott in 1918, it was initially classified as a crustacean.