NEW YORK (AP) — New fossils are providing critical details about one of the earliest known fishes, and researchers say that helps show how jaws evolved in animals that have backbones.

The fish is called Metaspriggina (me-tuh-SPRIG’-ih-nuh). Researchers say it grew about 2 inches long and lived widely in North America some 515 million to 500 million years ago.

The fish had no jaws. But Jean-Bernard Caron of the Royal Ontario Museum in Toronto, one of the study authors, said structures near the gills show what the precursor to jaws looked like.

A new description of the fish, based on fossils found mostly in British Columbia, was released Wednesday by the journal Nature.

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Online: Journal: http://www.nature.com/nature