Digit (anatomy) - Bird and Theropod Dinosaur Digits

Bird and Theropod Dinosaur Digits

See also: Digit homology in avians

Birds and theropod dinosaurs (from which birds evolved) have three digits on their hands. Paradoxically the two digits that are missing are different: the bird hand (embedded in the wing) is thought to derive from the second, third and fourth digits of the ancestral five-digit hand. In contrast, the theropod dinosaurs seem to have the first, second and third digits. Recently a Jurassic theropod intermediate fossil Limusaurus has been found in the Junggar Basin in western China that has a complex mix: it has a first digit stub and full second, third and fourth digits but its wrist bones are like those that are associated with the second, third and fourth digits while its finger bones are those of the first, second and third digits. This suggests the evolution of digits in birds resulted from a "shift in digit identity characterized early stages of theropod evolution"

Read more about this topic:  Digit (anatomy)

Famous quotes containing the word bird:

    With a broad shoehorn
    I am unstuffing a big bird in this dream
    Msomebody else’s holiday feast—
    and repacking the crop of my own,
    knowing it will burst with such
    onion, oyster, savory bread crust.
    Maxine Kumin (b. 1925)