Fossil Fish (named "Tiktaalik") Sheds Light on Transition

The 383 million-year-old specimens are described as crocodile-like animals with fins instead of limbs that probably lived in shallow water.Before these finds, palaeontologists knew that lobe-finned fishes evolved into land-living creatures during the Devonian Period.But fossil records showed a gap between Panderichthys, a fish that lived about 385 million years ago which shows early signs of evolving land-friendly features, and Acanthostega, the earliest known tetrapod (four-limbed land-living animals) dating from about 365 million years ago."The really remarkable find came when one of the crew found a snout of a flat-headed animal sticking out of the side of a cliff - that is totally what you want to find because if you are at all lucky the rest of the skeleton is back in the cliff," said Professor Shubin.The team found three near-complete, well-preserved fossils of the new species, Tiktaalik roseae, in an area of the Arctic called the Nunavut Territory. The largest measures almost 3m (9 ft) in length.The creature shares some characteristics with a fish; it has fins with webbing, and scales on its back.But it also has many features in common with land animals. It has a flat crocodile-like head with eyes positioned on top and the beginnings of a neck - something not seen in fish."When we look inside the fin, we see a shoulder, we see an elbow, and we see an early version of a wrist, which is very similar to that of all animals that also walk on land," said Professor Shubin."Essentially we have an animal that is built to support itself on the ground."

Tiktaalik - the name means "a large, shallow-water fish" in the Inuit language Inuktikuk - shows that the evolution of animals from living in water to living on land happened gradually, with fish first living in shallow water.The animal lived in the Devonian era lasting from 417m to 354m years ago, and had a skull, neck, and ribs similar to early limbed animals (known as tetrapods), as well as a more primitive jaw, fins, and scales akin to fish.The near-pristine fossil was found on Ellesmere Island, Canada, which is 600 miles from the north pole in the Arctic Circle.Scientists from the Academy of Natural Sciences in Philadelphia, the University of Chicago, and Harvard University led several expeditions into the inhospitable icy desert to search for the fossils.
The find is the first complete evidence of an animal that was on the verge of the transition from water to land. "The find is a dream come true," said Ted Daeschler of the Academy of Natural Sciences.
"We knew that the rocks on Ellesmere Island offered a glimpse into the right time period and were formed in the right kinds of environments to provide the potential for finding fossils documenting this important evolutionary transition."When Tiktaalik lived, the Canadian Arctic region was part of a land mass which straddled the equator. Like the Amazon basin today, it had a subtropical climate and the animal lived in small streams. The skeleton indicates that it could support its body under the force of gravity.

"Most of the major joints of the fin are functional in this fish," Professor Shubin said."The shoulder, elbow and even parts of the wrist are already there and working in ways similar to the earliest land-living animals."
Dr Clack said that, judging from the fossil, the first evolutionary transition from sea to land probably involved learning how to breathe air. "Tiktaalik has lost a series of bones that, in fishes, covers the gill region and helps to operate the gill-breathing mechanism," she said. "The air-breathing mechanism it had would have been elaborated and having lost the series of bones that lies between the head and the shoulder girdle means it's got a neck, it can raise its head more easily in order to gulp the air.
"The flexible robust limbs appear to be connected with pushing the head out of the water to breathe the air."

Creatures with features of both fish and land-living animals have been found before. Fish that may have been beginning to 'walk' in shallow water have been found from about 385 million years ago, and fish with limbs that bear digits have been seen from more than 365 million years ago.Specimens that fall into the gap, such as Tiktaalik, help researchers to work out the details of this transition. The newly found animal has a structure on its head that looks like a small gill slit that is on its way to becoming an ear, for example, and a long snout that would have been suited to catching prey on land.

Daeschler and Shubin set off to find this missing link in the evolutionary chain back in 1999. The pair targeted Ellesmere Island after noticing that it was listed in an undergraduate textbook as exposed Devonian rock that had not previously been explored for vertebrate fossils.The desolate area was reachable only by plane, and the weather was so bad that field work could only be done for about two months each summer. The team first walked around the rocky outcrops looking for fossils of plant life that indicated stream or delta sediments, in order to target areas that had once hosted shallow waters. "That is where the action is on the fish-to-tetrapod transition," says Daeschler.

faith writes: ... consistent with geology and the Flood.

What I am curious about is how well this find matches what was proposed for the back half based on previous finds of only the front portion.

How do they know it's the same individual? The Sciencedaily article doesn't seem to make this clear.