CNN —Hundreds of millions of years ago, jawless fishes swam Earth’s seas, their brains protected on the outside by armored skin, and on the inside by plates made of cartilage. Scientists are still piecing together how modern vertebrates’ skulls evolved from these ancient fish ancestors, which were the first animals with backbones. The specimen — an articulated cranium that’s 455 million years old — belongs to the jawless fish Eriptychius americanus. Modern vertebrate descendants of jawless fishes make up two groups: vertebrates with jaws, and jawless hagfish and lampreys. “So it’s quite exciting.”Extracting the detailsThe fossilized head cartilage was excavated in 1949 and described in 1967 by the late paleontologist Robert Denison, a curator of fossil fishes at Chicago’s Field Museum of Natural History.

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Persons: jawless, ”, Richard Dearden, Robert Denison, Denison, Dearden, “, paleobiologist Lauren Sallan, Sallan, ” Sallan Organizations: CNN, Naturalis Biodiversity, Field, University of Birmingham, Okinawa Institute of Science, Technology Graduate University Locations: Colorado, Leiden, Netherlands, United Kingdom, Japan