Ancient Fish Fills Missing Link
Excavations carried out over six years in the treeless, grassless, soil-less Ellesmere Island in the Canadian territory of Nunavut, 750 miles from the North Pole, have yielded a remarkable treasure: a 375-million-year-old, scaly, fin-legged, flat-headed, swivel-necked creature called Tiktaalik roseae. Named after the Inuit word for "large shallow-water fish," Tiktaalik fills in one of the most significant gaps in evolutionary history—the transition between swimming fish and the first animals to walk onto land.
Paleontologist Neil Shubin, of the University of Chicago and the Field Museum of Natural History, and his colleague Ted Daeschler, of the Academy of Natural Sciences in Philadelphia, planned their Arctic search with great care. Three hundred seventy-five million years ago, the Canadian Arctic was near the equator, with a subtropical climate—a plausible place for an aquatic creature to venture from surf to turf. "Looking at the evolutionary tree, and knowing something about evolution and Earth history, we predicted there would be a Tiktaalik-like creature up there," Shubin says.
The four- to nine-foot-long creature had fins, which held limblike bones forming a shoulder, elbow, and wrist that could do a push-up; broad ribs and scales; and a neck that allowed the animal to swivel its head. "That the skull was disconnected from the shoulder is something we would not have expected in an animal that was still a fish," Daeschler says. "Our hypothesis is that it was an adaptation to shallow water and gave the animal more ability to hunt."
"What is really exceptional about Tiktaalik is that it is not some esoteric branch of evolution," Shubin says. "We are not looking at an evolutionary dead end. When we look at the origin of the neck in Tiktaalik, the origin of the wrist in Tiktaalik, we are talking about human history. We can trace our own history back to things like this. The transition we are seeing in these Devonian fish is a piece of our distant past."
>>Another great resource on this discovery is http://tiktaalik.uchicago.edu/