AP BIOLOGY

Detailed explanation-1: -Tiktaalik roseae has features of the skull, neck, ribs and appendages that are shared with the earliest limbed animals (tetrapods), as well as fishlike features such as scales and fin rays. This mosaic of features makes it a textbook example of a transitional fossil, say paleontologists.

Detailed explanation-2: -So why is Tiktaalik referred to as a transitional creature? Its mix of characteristics of fish and of tetrapods suggest that it represents one of the moments in the transition between fish and tetrapods.

Detailed explanation-3: -Paleontologists have uncovered new fossils from Tiktaalik roseae, which, while still a fish, is considered a transitional fossil that also has traits common to the first four-footed animals. This more complete picture of Tiktaalik suggests that the creature had strong, mobile hind fins.

Detailed explanation-4: -Tiktaalik is sometimes called a “fishapod, ” because it looks like a cross between the primitive lobe-finned fish that it lived amongst and the first four-legged animals (a group called “tetrapods” from tetra-, meaning four, and-pod, meaning foot).

Detailed explanation-5: -Tiktaalik provides clues about a key transition in the history of life. Now extinct, this organism was a close relative of one our own ancestors-the first vertebrate to evolve four limbs and crawl out onto dry land.