For over a century, scientists have been puzzled by a mysterious fossil called Helmetia expansa, an ancient arthropod from ...

For over a century, the Cambrian arthropod Helmetia expansa remained a mystery. Discovered by paleontologist Charles ...

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