Arthropods belong to an evolutionary branch – the ecdysozoa – that contains about half of all animal species, and the earliest fossil evidence of the group dates back 550 million years Arthropods belong to an evolutionary branch – the ecdysozoa – that contains about half of all animal species, and the earliest fossil evidence of the group dates back 550 million years New Scientist – News
Worm-like fossil is the oldest ancestor of spiders and crustaceans
