Anchiornis
Graphic representation of Anchiornis
- Tiaojishan Formation ( China)
Anchiornis was a small, bird -like dinosaur from the family of Troodontidae who lived in the early Jurassic ( Oxfordian ). The animal had well-developed feathers on arms and legs and thus four wings, like the dromaeosaurid Microraptor.
The first description was based on a nearly complete fossil that was found in the Tiaojishan Formation in Jianchang in the Chinese province of Liaoning. The fossil is now in the Paleontological Museum of Liaoning. There is only one type Anchiornis huxleyi.
Features
Anchiornis had one, seen from the side, triangular skull with a large anterior cranial window, which was separated from the forward of the eyes skull window only by a small bone clasp. His teeth were not cut.
The postcranial skeletons ( skeleton behind the skull ) is similar to all troodontids. The front legs but longer than the other and similarly troodontids long as the basal Dromaeosauriden and birds. On well-preserved type specimen is a significant fletching to detect. The forearm had ten long wing feathers, hand had eleven, the lower leg 12 to 13, the foot ten to eleven. Hand and arm swing were about the same length. In contrast to the conditions at the " first bird " Archaeopteryx and Microraptor the wider part of the wing was Anchiornis proximally (towards the body towards the center ). In addition to the flight feathers on the legs Anchiornis had two other types of springs. Similar tufts of down feathers, the filaments of which all came together at the base and contour feathers whose filaments were arranged along a long and solid quill. Despite these properties, the authors of the first description not believe Anchiornis was airworthy. The very long lower legs are rather an indication of an ongoing lifestyle.
In February 2010, a study was published in the journal Science, is reported in the melanosomes obtained from fossil in the feathers of Anchiornis. Melanosomes give the springs today's birds their color. Anchiornis to have been gray in color, have had on the front and hind legs on the head of a mohawk -like, reddish brown and white feather comb, fitted with black bands contour feathers.
Evolution and systematics
The discovery of Anchiornis is especially important, since it is a bird -like dinosaur exists which is older than Archaeopteryx. Until then, was seen as problematic that the bird-like dinosaurs were geologically younger than Archaeopteryx.
Anchiornis is so far the oldest Troodontidae found. Probably all advanced theropods developed very rapidly in the early and middle Jurassic. How Anchiornis, the basal dromaeosaurid Microraptor and the basal bird Pedopenna show emerged first flight feathers on the distal ( away from the center of the body located ) parts of front legs, hind legs and tail. In the course of further evolution they then migrated towards the body center. The large flight feathers on the tail and the hind legs were first reduced and then went completely lost.
The position of Anchiornis within the bird-like dinosaur cladogram shows the following:
Anchiornis
Mei
Other Troodontidae
Scansoriopteryx
Archaeopteryx
Birds ( Aves)