Ichthyostega

Ichthyostega is an extinct genus of Devonian tetrapods known from fossils in Greenland. Its anatomy combines fishlike traits with features associated with vertebrates living on land.

Tetrapod: A vertebrate with four limbs or descended from an ancestor with four limbs. Ichthyostega belongs to the early tetrapod lineage, though its limbs were not suited to ordinary walking on land.
Ichthyostega locomotion: The proposed ways Ichthyostega used its limbs, tail, and trunk to move. Its limb structure suggests that movement was not simply a four-legged version of modern walking.
Late Devonian: The final epoch of the Devonian Period, spanning roughly 383 to 359 million years ago. Ichthyostega lived during this interval, when early tetrapods diversified.
Tulerpeton: An extinct Devonian tetrapod genus known from fossils in Russia. It provides a comparison for how limb and digit anatomy varied among Devonian tetrapods.
Sarcopterygii: The vertebrate group comprising lobe-finned fishes and tetrapods. Its ancestry lies among sarcopterygian fishes, whose paired fins had internal bones.
Ichthyostega limb: The forelimb and hindlimb structure of Ichthyostega, including its digits and joints. The limbs bear tetrapod features but were stiff and poorly suited to efficient terrestrial gait.
Greenland: The world's largest island, located between the Arctic and Atlantic oceans. Ichthyostega fossils were discovered in Devonian rocks in eastern Greenland.
Ventastega: An extinct Devonian tetrapod genus known from fossils in Latvia. Its remains broaden the range of body forms known near the time of Ichthyostega.
Lobed fin: A fleshy paired fin supported by a central skeleton of bones and muscles. Lobed fins provide the structural background for the limb-like bones seen in early tetrapods.
Ichthyostega tail: The large tail of Ichthyostega, which retained fin rays and likely aided swimming. Its finned tail shows that aquatic propulsion remained significant despite its limbs.

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