About 375 million years ago, a pioneering fish crawled out of a prehistoric ocean and kick-started the evolution of salamanders, lizards, you, me and all other land vertebrates that have ever existed.

The circuits of neurons that govern walking, many have long thought, emerged sometime after that, as creatures transitioned from swimming to limb-based locomotion.

But a new report, published in the journal Cell on Thursday, overturns that notion, suggesting the template for walking originated in ancient fish millions of years before the first vertebrate ever ambled on dry land. The little skate, a fish closely related to sharks and rays, not only displays walking behavior on the seafloor, but uses neurons and genes that are nearly identical to the ones vertebrates use to walk on land, said Jeremy Dasen, an associate professor at the N.Y.U. School of Medicine’s Neuroscience Institute and senior author of the paper.

You can trace the heritage of little skates and land vertebrates back to a common ancestor that lived about 420 million years ago. This primitive fish gave rise to the vast majority of vertebrate species, including all fish with paired fins. Typically, these pectoral and pelvic fins — which correspond to forelimbs and hindlimbs in land vertebrates — are small and largely used for balance and steering. To really propel themselves, most fish wriggle their powerful tails.