Microraptor
| Microraptor | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Holotype fossil of Microraptor gui , the white arrows indicate feather prints |
||||||||||||
| Temporal occurrence | ||||||||||||
| Lower Cretaceous ( Barremium ) | ||||||||||||
| 130.7 to 126.3 million years | ||||||||||||
| Locations | ||||||||||||
|
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Microraptor | ||||||||||||
| Xu , Zhou & Wang , 2000 | ||||||||||||
| species | ||||||||||||
Microraptor ( Gr. Mīkros - "small", Latin raptor - "robber") was a genus of carnivorous dinosaurs from the group of Dromaeosauridae . So far, at least nine well-preserved skeletons have been described that belong to two species - Microraptor zahoianus and Microraptor gui . The finds come from the Chinese province of Liaoning from the rocks of the Jiufotang Formation ( Jehol group ) and are therefore around 130 million years old ( Barremium , Lower Cretaceous ).
In 2003, Chinese paleontologists discovered the well-preserved fossil skeleton of a Microraptor gui in the Jiufotang Formation in Liaoning Province . After examining the remains, the researchers concluded that the animal had asymmetrical feathers that were not only formed on the front extremities , but also on the hind legs. Accordingly, the little dinosaur had four wing-like structures. According to a hypothesis by the paleontologist Sankar Chatterjee and the retired aeronautical engineer R. Templin, who made corresponding model calculations, Microraptor gui is said to have been able to glide like a double-decker glider by the Wright brothers . To do this, the dinosaur must have held its forelegs stretched out to the side (as is known from modern birds) and held the hind legs with the feathered metatarsals parallel to each other. That way, the back legs would be a little deeper than the front legs.
The reason for this assumption is that due to their anatomy , microraptors would not have been able to spread their legs sideways or even flap their wings. According to the two researchers, the animals are said to have climbed the tops of high trees with the help of their claw-reinforced toes, in order to plunge into the depths from there on a glide. In this way - similar to today's flying squirrels - they should have slid from tree to tree in an energy-saving manner.
More recent attempts in the wind tunnel with a reconstructed model go in a similar direction: According to this, however, microraptors initially stretched their legs backwards and had less air resistance than with the double-decker position. The animal only adopted the biplane position towards the end of the gliding flight in order to be able to land better.
Archaeoraptor Sloan 1999 and Cryptovolans Czerkas et al. 2002 are considered synonyms of Microraptor .
features
Microraptor was described as the “smallest known non-bird dinosaur” - the type specimen of Microraptor zhaoianus (IVPP V12330) is estimated to be 47 cm long and weigh 0.2 kg. The fuselage was extremely short at about 4.7 cm in length. Two other specimens described in 2002 (CAGS 20-7-004 and CAGS 20-8-001) were larger and are estimated to be 63 cm in length and 0.6 kg in weight. The type specimen of Microraptor gui (IVPP V13352) is estimated to weigh about 1 kg and a length of about 77 cm.
Each of the two branches of the lower jaw probably had 19 closely packed teeth, more than other dromaeosaurids. The hands and feet were equipped with sharply curved claws; the second toe also had the enlarged sickle claw typical of dromaeosaurids. As with other dromaeosaurids, the tail showed strongly elongated, rod-like connecting elements (zygapophyses and chevron bones ), which in Microraptor reached almost to the sacrum . A fossil of Velociraptor mongoliensis (IGM 100/986) shows an anatomically compound tail that was horizontally S-shaped, suggesting considerable lateral mobility of the tail despite these connecting elements. However, the tail of Microraptor appears to have been rigid, as indicated by the very straight tails in various Microraptor fossils.
The skeleton is very similar to a bird. For example, the teeth on the front are imperfect, while the rear teeth show a less flattened crown and a narrowing between the tooth root and crown - this combination of features is unique to Microraptor ( autapomorphy ). Furthermore, it was ischial (ischium) plate-like and increases the sacral vertebrae. Microraptor had 24 to 26 caudal vertebrae - fewer than in other dromaeosaurids, but as many as in the "primordial bird" Archeopteryx . The middle caudal vertebrae were also greatly elongated - three to four times as long as the anterior vertebrae. Another bird-like feature was the long upper arm bone (humerus), which was longer than the shoulder blade (scapula).
Furthermore, Microraptor shows many similarities with the troodontids, in particular with the most basal known troodontid, Sinovenator . For example, both Sinovenator and Microraptor show completely edentulous anterior teeth in the upper and lower jaw, no pneumatic foramia (openings) at the centers of the vertebrae, and an approximately arctometatarsal foot. According to the researchers, these similarities between Microraptor and Sinovenator are not surprising, since the Troodontidae are considered to be close relatives of the Domaeosaurids and both Microraptor and Sinovenator are very basic representatives of their groups.
The second species, Microraptor gui , shares with Microraptor zhaoianus various features on the hand and foot bones that are missing in other dromaeosaurids, such as the extremely short phalanx III-2. Other features differentiate the two species from each other: The first finger of Microraptor gui was very short and the pubis was strongly curved at 120 °, while it was straight in Microraptor zhaoianus . In addition, the shinbone (tibia) was curved, and at the proximal end of the spoke (radius) sat a pronounced process, a point of attachment for the biceps muscle.
feathers
Microraptor had long feathers on its arms and legs that formed four wings. The outer of these long feathers were real flight feathers and showed asymmetrical feather flags - as in modern birds. The construction of these wings was like the modern birds: So the arm wing each consisted of the hand attached to primaries , which were significantly longer than the about 18 secondaries arm. The leg wings were constructed similarly to the arm wings: there were springs on the metatarsus and on the leg. The longest arm swing was 18 to 22 cm, those of the feet 12 to 19 cm long. The body was covered with 2.5 to 3 cm long down. On the head, about 4 cm long feathers, some with feather shafts, formed a hood, which was probably used for display, as is the case with today's birds. From the 15th to 18th caudal vertebrae, the tail showed feathers that could be up to 12 cm long and formed a diamond-shaped tuft.
According to investigations in 2012, it can be assumed that the plumage of Microraptor was colored black-blue and shimmered, similar to the plumage of a crow.
Paleobiology
Orientation of the springs
Xu and colleagues (2003) stated that the outermost arm feathers ran parallel to the hand and formed an extension of it, while the remaining feathers were increasingly perpendicular to the body. The outermost leg springs would have pointed backwards when the leg was stretched out. This interpretation is based primarily on the alignment and arrangement of the feathers in the well-preserved type specimen of Microraptor gui . However, the feathers of this fossil are not directly connected to the skeleton, but separated from it by a halo-like white area. Xu and colleagues suspected that the proximal spring ends, which should actually be in this area, were simply not preserved. Kevin Padian argues that the feathers may have been separated from the body after the death of the animal, which is why conclusions about the orientation and arrangement of feathers in living animals are questionable. Padian even doubts that the long leg feathers actually belonged to the leg; so the evidence is not sufficient to assume winged legs. Hone and colleagues (2010) examined the type specimen of Microraptor gui under ultraviolet light and were able to show that the feathers are also present in the white halo area and are directly connected to the skeleton. In some cases, the feathers even reach right down to the bones - this is the case on the right metatarsus and in the chest area (furcula and sternal plates). Only carbonized feather sections appear under visible light , which can be clearly seen as black spots on the rock plate. Hone and colleagues interpret the white halo as an area in which the feathers could either not carbonize after the death of the animal, because they were chemically changed by the body tissue, or because they were covered by other, decomposing body tissue. In modern birds, feathers are anchored deep in the tissue and partly connected to bones of the skeleton. The same applies to dromaeosaurids - Velociraptor and Rahonavis have long feathers ( quill knobs ) on the ulna of the forearm. Hone and colleagues conclude from this that the springs in the Microraptor gui type fossil have not shifted or have shifted only minimally and reflect the original configuration.
swell
- ↑ a b c Alan H. Turner, Diego Pol, Julia A. Clarke, Gregory M. Erickson, Mark A. Norell : A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight. In: Science . Vol. 317, No. 5843, 2007, pp. 1378-1381, doi : 10.1126 / science.1144066 , digitized version (PDF; 507.41 kB) , Supporting Online Material (PDF; 755.11 kB) .
- ^ PBS Nova: The Four-Winged Dinosaur. 2008, transcript ; Interactive demo ( Flash ).
- ↑ Senter P. et al. (2004): Systematics and evolution of Dromaeosauridae (Dinosauria, Theropoda) in: Bulletin of the Gunma Museum of Natural History 8: 1-20; The Paleobiology Database: Microraptor (accessed: March 29, 2020)
- ↑ a b Xing Xu , Zhonghe Zhou , Xiaolin Wang: The smallest known non-avian theropod dinosaur. In: Nature . Vol. 408, No. 6813, 2000, pp. 705-708, doi : 10.1038 / 35047056 .
- ↑ a b Sankar Chatterjee , R. Jack Templin: Biplane wing planform and flight performance of the feathered dinosaur Microraptor gui. In: Proceedings of the National Academy of Sciences of the United States of America . Vol. 104, No. 5, 2007, pp. 1576–1580, digitized version (PDF; 967.30 kB) .
- ↑ a b c d e Xing Xu, Zhonghe Zhou, Xiaolin Wang, Xuewen Kuang, Fucheng Zhang, Xiangke Du: Four-winged dinosaurs from China. In: Nature. Vol. 421, No. 6921, 2003, pp. 335-340, doi : 10.1038 / nature01342 .
- ^ Mark Norell, Peter J. Makovicky : Important features of the dromaeosaurid skeleton. 2, Information from newly collected specimens of Velociraptor mongoliensis (= American Museum Novitates. No. 3282, ISSN 0003-0082 ). American Museum of Natural History, New York NY 1999, online .
- ↑ a b c Sunny H. Hwang, Mark A. Norell, Ji Qiang, Gao Keqin: New Specimens of Microraptor zhaoianus (Theropoda: Dromaeosauridae) from Northeastern China (= American Museum Novitates. No. 3381). American Museum of Natural History, New York NY 2002, online .
- ↑ Xing Xu: Deinonychosaurian Fossils from the Jehol Group of Western Liaoning and the Coelurosaurian Evolution. Chinese Academy of Sciences, Beijing 2002 (dissertation).
- ^ Li, Q .; Gao, K.-Q .; Meng, Q .; Clarke, YES; Shawkey, MD; D'Alba, L .; Pei, R .; Ellision, M .; Norell, MA; Vinther, J. (2012). Reconstruction of Microraptor and the Evolution of Iridescent Plumage. Science. 335 (6073): 1215-1219. doi: 10.1126 / science.1213780
- ↑ Kevin Padian : Four-winged dinosaurs, bird precursors, or neither? In: BioScience. Vol. 53, No. 5, 2003, ISSN 0006-3568 , pp. 451-453, digitized version (PDF; 437.23 kB) .
- ↑ Kevin Padian, Kenneth P. Dial: Origin of flight: Could 'four-winged' dinosaurs fly? In: Nature. Vol. 438, No. 7066, 2005, p. E3, doi : 10.1038 / nature04354 .
- ^ Alan H. Turner, Peter J. Makovicky, Mark A. Norell: Feather Quill Knobs in the Dinosaur Velociraptor. In: Science. Vol. 317, No. 5845, 2007, p. 1721, doi : 10.1126 / science.1145076 , digitized version (PDF; 158.81 kB) .
- ↑ Luis M. Chiappe , Gareth J. Dyke : The early evolutionary history of birds. In: Journal of the Paleontological Society of Korea. Vol. 22, No. 1, 2006, ISSN 1225-0929 , pp. 133–151, digitized version (PDF; 697.54 kB) .
- ↑ David WE Hone, Helmut Tischlinger, Xing Xu, Fucheng Zhang: The Extent of the Preserved Feathers on the Four-Winged Dinosaur Microraptor gui under Ultraviolet Light. In: PLoS ONE . Vol. 5, No. 2, 2010, e9223, doi : 10.1371 / journal.pone.0009223 .
