The extinct fish considered a transitional fossil between fish and land vertebrates is Tiktaalik. It lived about 375 million years ago during the Late Devonian, when vertebrate evolution was producing animals increasingly suited to shallow water and the first stages of life on land.
Tiktaalik combined fish features—including scales, gills, and fins—with tetrapod-like traits. Its broad, flattened skull, movable neck, robust ribs, and fin skeleton containing bones comparable to a shoulder, elbow, and wrist suggest that it could support or maneuver its body in very shallow water. Some evidence also points to primitive air-breathing adaptations.
The first fossils were discovered in 2004 on Ellesmere Island in Nunavut, Arctic Canada, and formally reported in 2006. Its name comes from an Inuktitut word meaning “large freshwater fish.”
Tiktaalik is sometimes called a “missing link,” but that phrase can mislead. It was not claimed to be the direct ancestor of modern land vertebrates; instead, it represents one evolutionary branch near the fish-to-tetrapod transition. Panderichthys is another close relative, but Tiktaalik is the standard quiz answer.