The fossil fish discovered in Arctic Canada and regarded as a transitional form between fish and tetrapods is Tiktaalik.
Tiktaalik was a lobe-finned fish that lived during the Late Devonian, about 375 million years ago. Its fossils were discovered on Ellesmere Island in Nunavut, Canada, in 2004, and the finding was formally reported in Nature in 2006.
The animal combined fish traits—scales, gills, and fins—with features associated with early tetrapods. Its broad skull, movable neck, ribs, and robust fin bones including wrist-like elements suggest that it could support part of its body in shallow water or on muddy surfaces. It may also have possessed primitive lungs.
Tiktaalik is often called a “missing link,” but that wording is misleading. It is not known to be the direct ancestor of modern land vertebrates. Instead, it is a close relative that helps document the evolutionary transition from fin-supported fish to four-limbed vertebrates. Coelacanths are also lobe-finned fish, while Acanthostega and Ichthyostega are more advanced early tetrapods.