Archeopteryx , London specimen with well-preserved feathers
|Upper Jurassic ( Tithonian )|
|152.1 to 145 million years|
|von Meyer , 1861|
Archeopteryx (from ancient Greek ἀρχαῖος archaios "ancient" and πτέρυξ pteryx "wings swing spring" Pronunciation Archeo-pteryx; mutatis mutandis "ancient rocker" or "Urschwinge") is a genus of Archosaurier whose fossils in the Frankish Alb in the Solnhofen limestone from the Upper Jurassic were discovered. Archeopteryx is considered to be a transitional form thatmediatesbetween theropod dinosaurs and birds . Since the archeopteryx, which is about the size of a dove , is usually attributed to the birds as a form close to the origin, the members of the genus are also referred to as primordial birds .
Archeopteryx was first described in 1861 by Hermann von Meyer on the basis of an isolated pen print . The first skeleton specimen (the so-called London specimen) was discovered in the same year and is mentioned in the first publication. To date, at least 11 other skeletal finds of varying degrees have followed.
The genus Archeopteryx shows a mosaic of primeval , i.e. reptilian-like features (for birds) , which were later discarded by modern birds ( neornithes ), and derived , i.e. bird-typical features (which, however, according to current knowledge, are only partially characteristic apply to birds).
Urtümlich include the presence of teeth and belly fins (Gastralia), a long tail spine, a relatively small number unfused sacral vertebra (Sakralia), unfused metacarpal , metatarsus - and tarsus - and pelvic bone , the three fingers claws and the lack of bony sternum .
Typical bird features include the modern-looking asymmetrical flight feathers , the clavicles fused to form a fork bone and the first toe ( hallux ) of the foot ( anisodactyl bird's foot ) oriented backwards or laterally-backwards .
Archeopteryx reached about the size of ravens (approx. 50 cm body length) and a weight of 0.8 to 1 kg.
The bird characteristics of the primeval bird have also been proven for some feathered dinosaurs or, as in the case of the reverted first toe of the Archeopteryx , not unchallenged. Therefore, some palaeontologists do not see the primitive bird as much more bird-like than some theropod dinosaurs that are not classified as birds (e.g. microraptors ).
Over the past 20 years, a variety of fossils of primitive birds and bird-like dinosaurs have been discovered, particularly in sedimentary rocks of the Lower Cretaceous of northeast China (the Jehol group ). Thus, Archeopteryx does not stand alone as a mosaic form, but can be classified in a ( morphological , not temporal) sequence of dinosaurs, which gradually become more similar to birds.
Proponents of the hypothesis that the flapping flight of birds originated from gliding from an elevated point, interpret the claws of Archeopteryx as those of a tree climber who slid down from the branches. In palaeological investigations of the find horizons, however, some researchers came to the conclusion that there must have been a hot and dry climate at the place where the Solnhofen limestone was formed and that there were probably no trees. In return, however, they pointed out high cliffs on the coast of the Jurassic Sea, which could be used as a starting point for first flight attempts. Burgers and Chiappe showed that Archeopteryx could possibly also launch from the ground.
The latest research, which examined the eleventh known fossil with the best-preserved plumage to date, assumes that the bird's plumage was not primarily used to fly, but only to warm the animal. This realization also came through a comparison with other feather shapes in dinosaurs. In addition, the arm swings were used to keep balance when running fast, were useful for breeding, and also served as camouflage and decoration.
Significance for the implementation of the evolution theory
Charles Darwin had predicted in the evolution theory he developed in 1859 that in the development of new species there should be transitional forms that still have to have characteristics of the old, but also characteristics of the new group. When Darwin published his theory, no such fossils were known, they were therefore as missing links ( missing links ), respectively. Only two years later, the first skeleton specimen of the Archeopteryx was found.
The Archeopteryx finds were the earliest geological evidence of vertebrate feathers. The fact that they already had clear characteristics of birds, but also those of reptiles and dinosaurs, made Archeopteryx an important indicator for the correctness of Darwin's theory of evolution . The dispute over the theory of evolution thus also became a dispute over Archeopteryx .
Richard Owen wrote the first description of the London specimen (see picture above). Because of his religious convictions, he rejected the theory of evolution and meticulously avoided any reference to the possible interpretation as a mediating link between reptiles and birds. There were gross errors in his description. Owen, then the first superintendent of the British Museum's natural history collection, bought the fossil, contrary to the express instructions of the board of directors. With the purchase, Owen wanted to prevent Darwin's theory of evolution from being supported by the primitive bird. Only Thomas Henry Huxley gave a systematic description of the London specimen and interpreted it as evidence for the theory of evolution. This cleared the way for the theory of evolution and its followers - in one of the most important scientific institutions in the world.
So far twelve more or less well-preserved skeletons of the genus Archeopteryx and a single feather have been found. All specimens came from the layers of the upper white Jura in the quarries near Eichstätt , Solnhofen , Langenaltheim , Jachenhausen near Riedenburg and Schamhaupten . The imprint of the individual feather was discovered in 1860, the first skeleton in 1855 ("Haarlem copy") and the last copy so far in 2011. These are the following pieces (sorted by the time at which the respective find was first recognized as Archeopteryx ) :
1. "The feather", discovered in 1860 in the municipality of Solnhofen and described in 1861 by the Frankfurt vertebrate paleontologist Hermann von Meyer (1801–1869), who coined the generic name Archeopteryx , which is still valid today , was the first known find. One part of the impression is in the Museum für Naturkunde in Berlin, the other side in the Paleontological Museum in Munich . It is not known whether the isolated feather actually came from Archeopteryx . For a long time, however, this specimen was problematically the holotype . A new investigation of the feather published in early 2019 showed that it did not come from Archeopteryx , but from another primeval bird or from a small, feathered, non-bird dinosaur.
2. The "London copy", found in 1861 on the Langenaltheimer Haardt near Solnhofen, is one of the three most important examples. It was the first complete find of a skeleton and is the type specimen of the species Archeopteryx lithographica . A few months after the find, the London Natural History Museum (then still part of the British Museum ) acquired the copy from its owner, the Pappenheim district doctor Carl Friedrich Häberlein (1787–1871). The driving force behind the purchase was the British naturalist Richard Owen , then head of the natural history collection of the British Museum and a declared opponent of Darwin's theories. With the purchase, Owen wanted to prevent Darwin's theory of evolution from being supported by the primitive bird. The fossil remained under lock and key for a long time and research results were only published gradually.
3. The “Berlin copy” (found between 1874 and 1876 on the Blumenberg near Eichstätt ), with its clear feather prints and a preserved skull, is probably the most beautiful and complete piece. The finder Jakob Niemeyer exchanged the find for a cow worth 150 to 180 marks . The new owner Johann Dörr, a quarry owner, sold it for 2,000 marks to Ernst Otto Häberlein (1819–1886) from Pappenheim , the son of the seller of the London specimen, who also prepared the find. The Bavarian State Collection and Yale University were initially interested in the find, but neither of them could afford the high purchase price. Even a request from German zoologists to Kaiser Wilhelm I was unsuccessful. Finally, Werner von Siemens acquired the copy in 1879 for 20,000 marks and gave it to the Mineralogical Museum of the Humboldt University in Berlin as a permanent loan . Two years later, the university reimbursed the lender Siemens the purchase price. The specimen has belonged to the Museum für Naturkunde in Berlin since then and has been on permanent display there since 2007.
4. The "Maxberger Exemplar" (1956 on the Langenaltheimer Haardt near Solnhofen) is a torso with some feather prints. It was in private ownership until the death of its discoverer Eduard Opitsch in 1991 and has been considered lost ever since.
5. The "Haarlem copy" (1855 in Jachenhausen near Riedenburg ) was found as early as 1855, five years before the spring, but it was not assigned to Archeopteryx until 1970 by John Ostrom . This specimen was classified as Pterodactylus crassipes by Hermann von Meyer in 1860 , so its species name crassipes should have replaced the name lithographica in accordance with the priority rules for naming fossils . This was prevented by the energetic use of Eastern Stream. The fragment is in the possession of the Teylers Museum, Haarlem . A new investigation of the fossil published at the end of 2017 revealed that it is not Archeopteryx , but rather a theropod closely related to Anchiornis , a small, bird-like but non-flightable dinosaur. It was described under the scientific name of Ostromia .
6. The "Eichstätter specimen" (1951 in Workerszell near Eichstätt ) was initially considered a small predatory dinosaur Compsognathus , was rediscovered in 1973 and described in 1974 by Peter Wellnhofer . The piece is owned by the Jura Museum in Eichstätt.
7. The "Solnhofen specimen" was discovered in the 1960s by a Turkish guest worker near Eichstätt and initially also misidentified as Compsognathus , but described in 1988 by Peter Wellnhofer. It is located in the Mayor Müller Museum in Solnhofen. In 2001, the Nuremberg Higher Regional Court ruled that the fossil did not have to be returned to a quarry owner who had claimed that it had been stolen from his property in 1985. The rejection of the lawsuit is now final, but the actual origin has still not been fully clarified.
8. The "copy of the Solnhofener Aktienverein" (found in summer 1992 in a quarry of the Solnhofer Aktien-Verein AG on the Langenaltheimer Haardt near Solnhofen) can be viewed in the Paleontological Museum in Munich. In 1993 the find was introduced to science by Peter Wellnhofer as a new species Archeopteryx bavarica . The beautiful feather prints and the very well preserved skeleton made numerous new discoveries possible. The structure described by Wellnhofer as the sternum , however, has been shown to be part of the raven bones according to recent studies . The possibly quite good flight skills are retained, however, since the sternum was probably present as a cartilaginous structure. Numerous details of the skull, jaw and tail of the magpie-sized primeval bird opened up new perspectives on the evolution of birds. Due to these peculiarities, this last great find is undoubtedly one of the three most important, some even consider it more beautiful than the Berlin copy.
9. A very fragmentary, ninth find (copy no. 8) had only been documented by a cast since 1997, and for a long time the owner and location were unknown. In 2009 the fossil dealer Raimund Albersdörfer presented the specimen he had acquired to the public for the first time at the Munich Mineral Days. The fossil was found in the Daiting parish in the late 1980s .
10. In 2004 another, also fragmentary find was reported, which is now in the Bürgermeister-Müller-Museum Solnhofen.
11. The "Thermopolis copy" was bought in 2005 by the owner of the Wyoming Dinosaur Center in Thermopolis and examined by Gerald Mayr, among others. The results were published in the December 2005 issue of Science . What is outstanding about the new specimen, in addition to its extremely good state of preservation, is the fact that for the first time the head can be seen from above and the metatarsal bone has an upward-pointing appendage.
12. In 2011, the 11th specimen was presented to the public for the first time, which had already been discovered several decades ago in the Eichstätt area. It is characterized by a particularly good feather preservation - similar to the "Berlin copy". A Munich paleontologist team from the Ludwig Maximilians University / Bayer. State Collection for Paleontology and Geology presented the far-reaching results in the July 2014 issue of Nature (with Archeopteryx as the cover picture).
13. The so far last (12th) specimen was discovered in 2010 by a finder, whose name is kept secret, in an adventure quarry in Schamhaupten in the Eichstätt district on the eastern edge of the Kösching Forest. At 153 million years old, it is believed to be the oldest Archeopteryx specimen to date. Still in the possession of the finder, the fossil is claimed by the owners of the quarry in order to use it for museum purposes. It is exhibited in the museum of the Altmühltal Dinosaur Park , which opened in August 2016 , about 10 km from the site.
Most of the Archeopteryx specimens show a crooked cervical spine. This typical backward curvature only developed after the death of the animals in the water grave.
Archeopteryx is usually defined as the most primitive bird, that is, all species that are more distantly related to the modern birds ( neornithes ) than Archeopteryx are considered not to belong to the birds. Among the Mesozoic birds there are some that are only slightly more closely related to today's birds than Archeopteryx : Rahonavis and Jeholornis have in common with Archeopteryx, among other things, the long bony tail that more developed birds ( Pygostylia ) have deposited.
Within the theropod dinosaurs , the deinonychosaurs are close relatives of the birds - both groups are combined in the parent group Paraves (Eumaniraptora). A feature that connects the deinonychosaurs with Archeopteryx and Rahonavis is the hyperextensible second claw of the foot. Feathers with a closed feather flag were probably already developed by the ancestors of the Paraves.
According to Benton (2005), the following relationships exist within the paraves:
There are a number of phylogenetic analyzes that have come to different results with regard to the relationships between bird-like deinonychosaurs and primeval birds. According to the hypothesis of Mayr et al. a. some feathered dromaeosaurids like Microraptor were more closely related to the Pygostylia than Archeopteryx ; in the group of birds the flight of birds might have arisen several times independently of one another.
Critics of the dinosaur ancestry of birds believe that the resemblance of primitive birds to theropod dinosaurs is due to massive convergent evolution . According to Feduccia et al. a. (2005) the birds emerged from a group of primeval archosaurs that has yet to be determined , while microraptors and other feathered dinosaurs were in fact not dinosaurs but rather early forms of flightless birds.
Archeopteryx and Xiaotingia
The inclusion of an Archeopteryx- like dinosaur of the late Jurassic Tiaojishan Formation ( Liaoning , China) named in 2011 due to new fossil finds in a phylogenetic analysis led to the fact that the previously assumed relationships of Archeopteryx were questioned. The analysis showed that Archeopteryx together with the new genus Xiaotingia , which resembles deinonychosaurs in some features, could have been more closely related to deinonychosaurs than to later birds:
According to this hypothesis , depending on the definition of the group of birds, Archeopteryx would either not belong to the birds or the birds would also include the deinonychosaurs.
Whether the Archeopteryx finds belong to one or more species has been controversial since the first description of the Berlin specimen, which is reflected in the accumulation of synonymous generic and species names that have been assigned to the same specimens and then revised.
In his revisions, Elzanowski assigned the specimens known at the time to four different species, suggesting that the Solnhofen specimen, which in his opinion deviated particularly clearly from the others anatomically, belonged to its own genus:
- Archeopteryx lithographica , holotype : London specimen;
- Archeopteryx siemensii , holotype: Berlin specimen;
- Archeopteryx bavarica , holotype: Munich specimen;
- Wellnhoferia grandis , holotype: Solnhofener specimen.
The finding that the previously known Archeopteryx specimens do not belong to a single species is confirmed by Mayr et al. a. (2007) confirmed. In their description of the Thermopolis specimen, they compare the last find so far with previously known fossil material from Archeopteryx . Contrary to Elzanowski's analysis, they come to the conclusion that the existing differences between the ten skeletal finds do not justify more than two types:
- Archeopteryx lithographica , holotype: London specimen, also belonging to the Solnhofen specimen;
- Archeopteryx siemensii , holotype: Berlin specimen, also belonging: Munich specimen, Thermopolis specimen.
In 2018 , the new species Archeopteryx albersdoerferi was built on the basis of the Daitinger specimen, geologically the youngest Archeopteryx specimen .
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