How arthropods got their legs
Fossils show flaps that fused to make modern limbs
Newly discovered fossils fill a gap in scientists’ knowledge of how arthropods evolved their legs. The extinct creatures’ limblike flaps represent a stage before the two parts fused into the limbs seen in many arthropod species now living.
The fossils, which belong to a group of very early arthropods called anomalocaridids, were found from 2009 to 2014 in Morocco. The earliest anomalocaridids lived 530 million years ago, during the Cambrian Period. Paleontologists thought that the group had gone extinct by 505 million years ago, but the fossils of the new species, named Aegirocassis benmoulae, are 480 million years old.