ABOVE: Scientists are calling this new species a “fishapod,” since it is an intermediate between fish and four-legged land animals called tetrapods. It could use its fins like limbs to prop up its body. Illustration: Kalliopi Monoyios BELOW: This newly discovered species, Tiktaalik roseae, walked out of the water onto land about 375 million years ago. Photo: Ted Daeschler.
	The valley in Bird Fiord where the team camped and made its discovery. Photo by Ted Daeschler

HEADLINE SCIENCE: Fish Out Of Water

A new fossil find catches fish in the act of evolving into the first land-dwelling vertebrates.

Creationists and intelligent design supporters often claim that the lack of “transitional” animals in the fossil record proves that evolution did not and does not take place. In fact, there are many examples of species – both living and extinct – that demonstrate evolutionary transitions from one body type to another. The newest species to make this list is Tiktaalik roseae, a fish that lived about 375 million years ago in the shallow waters of what is now the Canadian Arctic.

This prehistoric predator had fishlike fins, gills, and scales, but its neck, head, and ribs resembled those of the earliest land-dwelling vertebrates. Unlike other fish, which lack necks, Tiktaalik would have been able to turn its head from side to side – an essential skill for land-dwelling animals. Its heavy ribs also suggest that it spent some time on land, since water supports the weight of aquatic animals, making strong ribs largely unnecessary. External nostrils on its snout indicate that it could breathe air through its nose and lungs as well as through its gills. Additionally, the bones inside animal’s forward fins provide evidence of arms in the making. The beginnings of digits, wrists, elbows, and shoulders were all present, and would have allowed the fish to flex its proto-limbs on the floor of streams and perhaps pull itself up on the shore for brief stretches.

Previous fossils representing this evolutionary event have essentially been fish with a few land characteristics, or land vertebrates with a few residual fish characteristics. Tiktaalik’s semi-fishy features evenly split the difference between fish and early amphibians, helping to answer a number of questions about how the first land dwellers evolved.