Among those features are paired appendages — the mirrored arms and legs of many mammals — and a 370-million-year-old, long-extinct fish species discovered at a world-famous Quebec fossil site has been described as one of the earliest known exhibitors of such duality in a jawless fish.

The fossil creature, Euphanerops longaevus, thrived during the Devonian era — the so-called “Age of Fishes” — when marine animals were developing ever-more complex variations, and some of them evolved into the “lobe-finned” precursors of land vertebrates.

Perhaps the most famous of those lobe-finned fish — the Ellesmere Island fossil species Tiktaalik roseae, discovered in 2006 — has helped scientists bridge the gap between fish and the earliest tetrapods, the four-footed creatures that eventually encompassed dinosaurs, deer and humans and which would come to dominate life on land.

But Euphanerops longaevus, first unearthed in 1900 at the renowned Miguasha fossil site on Quebec’s Gaspé Peninsula, represents a time when even simple, jawless fish were evolving novel anatomical structures as organisms worked out the optimal arrangements of fins and limbs.