The Senegal bichir represents an ancient ray-finned lineage that split from the lobe-finned line long before vertebrates moved onto land.

Polypterus Lineage: About 380 million years ago, during the Devonian Period — often called the “Age of Fishes” — the lineage leading to today’s bichirs branched off from other ray-finned fishes (Actinopterygii). This branch occurred early, very early, near the base of the ray-finned radiation. The Senegal bichir, Polypterus senegalus, is a modern descendant of that deep split.

Pictured: The Senegal bichir still breathes air. It possesses paired lungs in addition to gills and can survive in low-oxygen waters by gulping at the surface. Its thick, diamond-shaped ganoid scales resemble armor more than fish scales. Along its back runs a series of small dorsal finlets — each with its own spine — a feature that looks almost prehistoric because it is.