AP BIOLOGY

Detailed explanation-1: -In particular, fossils of the Tiktaalik show that it had scales and gills like aquatic animals such as fish. However, it also had characteristics similar to tetrapods because of a flat head with eyes on top, a flexible neck, the presence of strong front and hind limbs, a robust pelvic girdle, a prominent hip joint.

Detailed explanation-2: -Tiktaalik retained both fish and tetrapod characteristics. Its fish characteristics include scales, fins, and gills, and its tetrapod characteristics include a neck, ribs capable of bearing weight, a flat head, dorsally positioned eyes, a fin skeleton, and ear notches (The University of Chicago, 2006).

Detailed explanation-3: -Its extraordinary blend of gills, scales, fins and lungs, combined with a movable neck, sturdy ribcage and crocodile-like head, placed Tiktaalik half way between fish and the earliest four-legged land animals.

Detailed explanation-4: -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-5: -Like a fish, the fossil of Tiktaalik shows evidence of scales, gills, and fins. But inside the fins, Tiktaalik contains limb bones that are characteristic of an early tetrapod.