Tiktaalik

Tiktaalik is an extinct genus of lobe-finned vertebrates from the Late Devonian, about 375 million years ago. Its fossils combine fish traits with features associated with early tetrapods, including a mobile neck and robust, limb-like fins.

Lobe-finned fish: Vertebrates whose paired fins have fleshy, internally supported bases. Tiktaalik belongs to this group, whose fin structure provides context for its limb-like appendages.
Pectoral fin: A paired fin attached to the pectoral girdle near a vertebrate's head. Its internal bones include structures comparable to an upper arm, forearm, and wrist.
Ellesmere Island: A large island in the Canadian Arctic Archipelago, extending into the Arctic Ocean. Tiktaalik fossils were found in Devonian rocks on this remote island.
Tiktaalik roseae: The type species of Tiktaalik, known from Late Devonian fossils found on Ellesmere Island. This is the named species represented by the best-known Tiktaalik fossils.
Eusthenopteron: An extinct Devonian lobe-finned fish with fin bones resembling the upper and lower bones of tetrapod limbs. It has limb-like internal bones but lacks several of Tiktaalik's more tetrapod-like features.
Tetrapod: A vertebrate with four limbs or descended from an ancestor with four limbs. Tiktaalik predates the familiar tetrapod body plan while preserving clues to its emergence.
Humerus: The single proximal bone of the forelimb in tetrapods and of the pectoral fin in many lobe-finned fishes. Tiktaalik's robust humerus could help brace its body against the bottom.
Nunavut: A territory of northern Canada established in 1999, covering much of the Canadian Arctic Archipelago. The fossil site lies in this territory's Arctic landscape.
Tiktaalik skull: The fossil skull of Tiktaalik, combining a flattened head with fish-like and tetrapod-like traits. Its eyes on top and mobile neck suit an animal living near the water's surface.
Acanthostega: An extinct Devonian aquatic tetrapod with digits on its limbs. It had digits, whereas Tiktaalik retained fins without digits.

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