University scientists dig up missing evolutionary link

By Emily Bell

A team of paleontologists led by University researcher Neil Shubin has discovered the fossils of a 375-million-year-old creature that is the missing evolutionary link between water-bound fish and the first animals to walk on land, according to two research articles published in the April 6 issue of Nature.

The team of scientists found the never-before-seen species Tiktaalik roseae on Ellesmere Island in the northern reaches of Canada’s Nunavut territory.

“We got the idea for this dig from an undergrad geological textbook,” Shubin said. “We look for rocks of the right age and type that are exposed at the surface. The Arctic was perfect.”

Shubin, professor and chairman of organismal biology, was the co-leader of a team that also included Edward B. Daeschler of the Academy of Natural Sciences in Philadelphia and Farish A. Jenkins Jr., a Harvard University evolutionary biologist. The National Geographic Society funded much of the research.

The scientists found several specimens of the new species. The quality of the fossils has allowed the scientists to challenge long-standing conclusions about the evolutionary progression from water animals to land animals.

“It was expected and unexpected,” Shubin said. “We expected to find an intermediate fossil at this time in the history of Earth. We did not expect to find such a beautiful one or one so well preserved.”

Convention among scientists before the discovery was that animals evolved to live and walk on land in response to environmental pressures. As their habitats began to dry, the animals that survived were ones who could move from pond to pond in search of food.

Analyses of Tiktaalik roseae, however, contradict that model. Though evidence of scales and fins in the specimens confirm that Tiktaalik was indeed a fish, the well preserved bones show evidence of joints capable of supporting weight on land in addition to a flattened body structure that implies a life spent in shallow water.

“Most of the major joints of the fin are functional in this fish,” Shubin said in a statement to the University News Office. “The shoulder, elbow and even parts of the wrist are already there and working in ways similar to the earliest land-living animals.”

The discovery has prompted a flurry of media attention in the last few days. “It’s been tiring, but it was a great opportunity to communicate science to the general public,” Shubin said.

The scientific name of the new species comes from a word in the language of the Inuits of Nunavut meaning “large, shallow water fish.” The fossils officially belong to the people of Nunavut and will be returned once analysis is complete.