Admin
Admin
Αριθμός μηνυμάτων : 8056
Registration date : 10/07/2008
 |  Θέμα: Αρχαιοπτέρυξ : Archaeopteryx 21.03.09 22:18 | |
| Archaeopteryx was a primitive bird that lived during the Tithonian stage of the Jurassic Period, around 150–145 million years ago.
The Berlin Archaeopteryx
The only specimens of Archaeopteryx that have been discovered come from Bavaria in southern Germany.
Archaeopteryx was roughly the size of a medium-sized modern-day bird, with broad wings that were rounded at the ends and a long tail compared to its body length. In all, Archaeopteryx could reach up to 500 millimeters (1.6 ft) in body length.
1880 photo of the Berlin Archaeopteryx specimen, showing leg feathers that were subsequently removed during preparation
Archaeopteryx feathers, although less documented than its other features, were very similar in structure and design to modern-day bird feathers.
The Thermopolis Specimen
However, despite the presence of numerous avian features, Archaeopteryx had many theropod dinosaur characteristics. Unlike modern birds, Archaeopteryx had small teeth[4] as well as a long bony tail, features which Archaeopteryx shared with other dinosaurs of the time.
Because it displays a number of features common to both birds and dinosaurs, Archaeopteryx has often been considered a link between them—possibly the first bird in its change from a land dweller to a bird. In the 1970s, John Ostrom, following T. H. Huxley's lead in 1868, argued that birds evolved from theropod dinosaurs and Archaeopteryx was a critical piece of evidence for this argument;
Replica of the London Archaeopteryx
it preserves a number of avian features, such as a wishbone, flight feathers, wings and a partially reversed first toe, and a number of dinosaur and theropod features.
For instance, it has a long ascending process of the ankle bone, interdental plates, an obturator process of the ischium, and long chevrons in the tail.
In particular, Ostrom found that Archaeopteryx was remarkably similar to the theropod family Dromaeosauridae.
The famous feather
The first remains of Archaeopteryx were discovered in 1861; just two years after Charles Darwin published On the Origin of Species.
Archaeopteryx seemed to confirm Darwin's theories and has since become a key piece of evidence in the origin of birds, transitional fossils debate and the confirmation of evolution.
Indeed, further research on dinosaurs from the Gobi Desert and China has since provided more evidence of a link between Archaeopteryx and the dinosaurs, such as the Chinese feathered dinosaurs.
The Munich Specimen
Archaeopteryx is close to the ancestry of modern birds, and it shows most of the features one would expect in an ancestral bird. However, it may not be the direct ancestor of living birds, and it is uncertain how much evolutionary divergence was already present among other birds at the time. | |
|
