An amphibious creature that lived 375 million years ago has turned out to be a "missing link" in the chain of events that led to the emergence of the first fish-like animals to walk on land.
The animal bears all the hallmarks of a primitive land animal, with limb-like appendages, a crocodilian head and tooth-filled jaws, but it still retains scales, fins and gills.
Scientists have described the discovery as one of the most important in the description of the evolutionary origins of all land-dwelling vertebrates. The "fish with fingers" lived in semi-tropical water and probably used its front limbs to prop itself up or to walk in rudimentary fashion on dry land for short periods.
Scientists found fossils of the creature, ranging in size from four to nine feet long, on Ellesmere Island in the Canadian Arctic, which 375 million years ago was part of a subtropical landmass that straddled the equator.
The researchers have called the species Tiktaalik roseae after an Inuit word for "large, shallow-water fish". Its description is published today in the journal Nature.
Neil Shubin, a professor of biology at the University of Chicago and one of the leaders of the research team, said: "Tiktaalik blurs the boundary between fish and land-living animals in terms of its anatomy and its way of life. This animal is both fish and tetrapod; we jokingly call it a 'fishapod'.
"Most of the major joints of the fin are functional in this fish. The shoulder, elbow and even parts of the wrist are already there and working in ways similar to the earliest land-living animals," Professor Shubin said.