Archaeopteryx is an iconic fossil, often thought of as the ‘missing-link’ between dinosaurs and birds. It was first described in 1861 by the German palaeontologist Hermann von Meyer (1801-1869). Since then Archaeopteryx has been the focus of controversy surrounding the origin of birds and their links with dinosaurs.
Oldest fossils of birds are found in lithographic stones of Upper Jurassic and are estimated to be nearly hundred forty million years old. First such fossil was discovered by Andreas Wagner in 1861 from lithographic rocks of Solenhofen in Bavaria (Germany). Wagner named it Gyphosaurus. Later, Hermann Von Meyer named it Archaeopteryx lithographica. It was kept in British museum. A second and more complete fossil was found in 1877 at a distance of twenty miles from the first one. It was named Archaeornis siemensi and was kept in Berlin museum. In 1956, third incomplete specimen was found. A few additional fragments have also been discovered.
First two fossils are preserved in such a condition that outlines of even feathers are clearly visible. According to T.J. Parker and W.A. Hasweli, the two fossils, Archaeopteryx lithographica and Archaeornis siemensi, belong to the same genus or even species, in which case name Archaeopteryx has priority. De Beer (1954) concluded that the two generic names are merely due to different sex or age, otherwise both the fossils are alike.
Reptilian Features of Archaeopteryx
- Non-pneumatic bones.
- Primitive vertebral column with no fusion of vertebrae.
- Separate ribs on all cervical vertebrae.
- Amphicoelous vertebrae, never heterocoelous.
- Sternum is boat shaped and without a keel.
- Long tail comprising of twenty unfused vertebrae and no pygostyle.
- Full abdominal set of ribs present.
- Claws are present on all three fingers of the fore arm.
- Teeth are present in both jaws.
- Ribs are without uncinate process.
- Body and limbs bear scales.
- Elongated ilium and backwardly directed pubis in the pelvic girdle is similar to those of reptiles.
- Palm or metacarpal bones are separate from one another.
Avian characters of Archaeopteryx
- Well developed feathers are present.
- Fore limbs are modified as wings.
- Skull bears large orbits and is monocondylic.
- Jaws are elongated and form a beak.
- Furcula or wish bone is present.
- First toe is opposable.
- Several bones of the cranium are fused as in modem birds.
- Tail feathers (rectrices) are present.
On the basis of aforesaid description, it can be said that birds originated from some reptilian ancestor.