Archaeopteryx
|
|
| Archaeopteryx Conservation status: Fossil | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
 A model of Archaeopteryx lithographica on display at the Oxford University Museum | ||||||||||||||||||
| Scientific classification | ||||||||||||||||||
| ||||||||||||||||||
| Binomial name | ||||||||||||||||||
| Archaeopteryx lithographica Meyer, 1861 |
Archaeopteryx lithographica is widely accepted as the earliest and most primitive known bird. The discovery of the first intact specimen in 1861, two years after Charles Darwin published The Origin of Species set off a firestorm of debate about evolution and the role of transitional fossils that endures to this day.
Since the discovery of a single feather in 1860, only seven additional specimens of Archaeopteryx have been found, all from the Late Jurassic Solnhofen limestone of southern Germany. The first skeleton is now housed at the Natural History Museum of London, and the most spectacular is the famed Berlin Specimen at the Humboldt Museum of Berlin.
In the 1990s, the discovery of a number of well preserved feathered dinosaurs in China solidified the link between dinosaurs and birds.
| Contents |
Primitive bird
Archaeopteryx was similar in size and shape to a poo magpie, with short, broad wings and a long tail. The feathers resemble those of living birds, but Archaeopteryx was rather different from any bird we know of today: it had jaws lined with sharp teeth, three fingers ending in curving claws, and a long bony tail.
Archaeopteryx.jpg
Archaeopteryx is a powerful piece of evidence that birds evolved from dinosaurs. The skeleton is most similar to the dinosaurs of the families Dromaeosauridae and Troodontidae. However, it is not anymore believed to be a direct ancestor of modern birds, but rather another example of the many theropod derivatives with any number of avian features that have been recognized as a major evolutionary trend of the Late Jurassic/Early Cretaceous, one (as of yet unidentifed, due to the general and primitive state of avian features) lineage of which eventually gave rise to modern birds.
Reports of an apparently earlier bird, Protoavis, are considered to be unproven by most paleontologists.
Fly or hop?
There is some controversy about whether Archaeopteryx could genuinely fly, or only hop around and glide from trees. The lack of a large breastbone suggests it was not a strong flier, but flight muscles might have attached to the bird's thick, boomerang-shaped wishbone. The large wings and long tail, however, suggest that it was both stable and maneuverable in the air. The shape of the wings is similar to birds which fly through trees and brush. In 2004, scientists analyzing Archaeopteryx's braincase concluded that its brain was significantly larger than that of most dinosaurs, indicating that it possessed the brain size necessary for flying.
Archaeopteryx continues to play an important part in scientific debates about the origin and evolution of birds. Some scientists see Archaeopteryx as climbing through the trees like a squirrel, following the idea that birds evolved from tree-dwelling gliders (the "trees down" hypothesis for the evolution of flight). Other scientists see Archaeopteryx as running quickly along the ground, supporting the idea that birds evolved flight by running (the "ground up" hypothesis). So far, Archaeopteryx has perhaps produced as many questions as answers, and the latest findings on this fossil are unlikely to be the last word.
Discoveries
Its name comes from the limestone in which the first discovered fossil was imprinted. The limestone was found in Solnhofen limestone formation in Germany. It was formed in the Jurassic, 150 million years ago, which is when the Archaeopteryx lived.
Taxonomy
The relationships of the specimens are problematic; most specimens have been given their own species at one point or another. The Berlin specimen has been referred to Archaeopteryx siemensii, the Eichstatt specimen to Jurapteryx recurva, the Munich specimen to Archaeopteryx bavarica and the Solnhofen specimen was referred to Wellnhoferia grandis. Recently, it has been argued that all specimens belong to the same species (New Scientist, 17 April 2004, p.17). However, significant differences exist between the specimens. In particular, the Munich and Eichstatt specimens differ from the London, Berlin, and Solnhofen specimens in being smaller, having different finger proportions, and in having more slender snouts lined with sharp teeth. These differences are as large or larger than the differences seen today between adults of different bird species. However, it is also possible that these differences could be explained by different ages.
The eight specimens are named after the city in which they are housed:
- The feather: Discovered in 1860 near Solnhofen, Germany, and described in 1861 by Hermann von Meyer. Currently located at the Humbolt Museum f?urkunde in Berlin. This is generally referred to Archaeopteryx, but whether it actually is a feather of this species or another, yet undiscovered, proto-bird is unknown.
- London Specimen (BMNH 37001, the holotype): Discovered in 1861 near Langenaltheim, Germany, and described in 1863 by Richard Owen, who made it the type specimen for the genera and species. Currently located at the British Museum of Natural History in London. It is missing its head.
- Berlin Specimen (HMN 1880): Discovered in 1876 or 1877 near Blumenberg, Germany, and described in 1884 by Wilhelm Dames. Currently Located at the Humbolt Museum f?urkunde. It is the best specimen, and the first with a complete head. Once classified as a new species, A. siemensii.
- Maxberg Specimen (S5): Discovered in 1956 or 1958 near Langenaltheim and described in 1959 by Heller. Currently missing, though it was once exhibited at the Maxberg Museum in Solnhofen. It belonged to Eduard Opitsch, who loaned it to the museum. After his death in 1992 the specimen was discovered to be missing, and may have been stolen or sold. It is composed of a torso.
- Haarlem Specimen (TM 6428, also known as the Teyler Specimen): Discovered in 1855 near Riedenburg, Germany and described as a Pterodactylus crassipes in 1875 by Meyer, it was reclassified in 1970 by John Ostrom. Currently located at the Teyler Museum in Haarlem, the Netherlands. The very first specimen, despite the classification error.
- Eichst䴴 Specimen (JM 2257): Discovered in 1951 or 1955 near Workerszell, Germany and described by Peter Wellnhofer in 1974. Currently located at the Jura Museum in Eichst䴴, Germany. It is the smallest specimen, as has the best head. Possibly a separate genus, Jurapteryx recurva, or species A. recurva.
- Munich Specimen (S6, formerly known as the Solnhofen-Aktien-Verein Specimen): Discovered in 1991 near Langenaltheim and described in 1993 by Wellnhofer. Currently located located at the Pal䯮tologische Museum M? in Munich. Only specimen with a breastbone (sternum). May be a new species, A. bavarica.
- Solnhofen Specimen (BSP 1999): Discovered in the 1960s near Eichst䴴, Germany and described in 1988 by Wellnhofer. Currently located at the B?eister-M?Museum in Solnhofen. It was originally classified as a Compsognathus by an amateur collector. May belong to a separate genus and species, Wellnhoferia grandis.