Protoavis
| Protoavis | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Temporal occurrence | ||||||||||||
| Upper Triassic | ||||||||||||
| 225 to 210 million years | ||||||||||||
| Locations | ||||||||||||
|
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Protoavidae | ||||||||||||
| Chatterjee , 1991 | ||||||||||||
| Scientific name | ||||||||||||
| Protoavis | ||||||||||||
| Chatterjee, 1991 | ||||||||||||
| Art | ||||||||||||
|
The term Protoavis ( "First Bird " - composed of ancient Greek πρῶτος Protos "the first" and Latin avis "bird") was awarded fossil bones found that in 1984 Post in the US state of Texas in layers of Dockum Group from the Upper Triassic found were. These were Archosauria remains, which have been described as a primitive species of bird - this would have put the origin of the birds back another 60 to 75 million years if correctly assigned.
Protoavis is said to have reached a size of 35 centimeters, its age is given as 225 to 210 million years BP. Although Protoavis is much older than Archeopteryx , its skeletal structure is said to be much more bird-like. Reconstructions show him as a carnivorous bird, whose teeth were sitting on the edge of the jaw and whose eyes were placed far in front of the skull - which indicates a crepuscular and nocturnal way of life. However, the bone finds are in a very bad state of preservation, so no further statements can be made about his flight ability. Even if reconstructions usually show it fletched, there is no clear evidence of this on a detailed study of the fossil material.
The first description assumes that Protoavis actually existed and that the reconstruction was carried out correctly. Almost all paleontologists doubt that Protoavis is a bird or a species in its own right - for them the remains are too fragmentary and the synapomorphies typical of birds are not convincing enough. The circumstances surrounding the discovery are not entirely trustworthy either - the remains were scattered within a tangled heap of dinosaur and other species' bones. The site itself indicates a mass extinction caused by a flash flood in a river delta.
Controversial find
Sankar Chatterjee of Texas Tech University believed that some of the broken pieces of bone belonged to two individuals of the same species, a young and an older animal. However, only a few fragments were found (a skull and several bones belonging to limbs), which also did not really fit in their proportions. For this reason, many specialists believe that Protoavis is a chimeric fossil composed of several organisms. The skull pieces are likely from a Coelurosaurier come, most of the limbs fragments indicate Cerato dinosaurs and at least some of the vertebrae resemble those of a Megalancosaurus - the latter way, is not a dinosaur, but a avicephaler Diapside .
“No matter how you want to twist and turn it, even the fossil fragments assigned to the Protoavis question its real existence. The minimal final demand is therefore that Chatterjee's provocative find is just a chimera, a confused bunch of long-dead archosaurs ”.
If Protoavis ever existed, it would raise interesting questions about when the birds split off from the dinosaurs. The status of the animal must remain in the dark until better evidence emerges. In addition, paleobiogeographical studies show that North and South America were only colonized by birds from the Cretaceous onwards. The oldest and most primitive evolutionary lines of indisputable birds have so far all been discovered in Eurasia . Certainly, the fossil remains found were assigned to primitive dinosaurs and other reptiles , as already explained above, according to Ockham's principle of thrift , but are coelurosaurs and ceratosaurs really that far removed from the ancestors of the first birds? In some ways their skeletons are quite similar - this also explains why these dinosaurs could be mistaken for avian-like ones. So was z. B. Archeopteryx was originally thought to be a small theropod dinosaur. Zhonghe Zhou draws the following conclusion:
" Protoavis never met with widespread support and was never seriously recognized as a Triassic bird ... Witmer, who studied the material and was one of the few Chatterjee's theory to seriously consider it, concluded that the avian status of P. texensis was by no means is as undisputed as it is usually pointed out by Chatterjee. He also recommended that Protoavis should be given less attention in the discussion about the ancestry of birds ”.
Disputes in evolutionary issues
It is sometimes said that Protoavis would refute the hypothesis that birds were derived from dinosaurs. However, this is not the case. The only consequence is that the time at which the two lines split goes further back into the past and that the Dromaeosauridae must be included in the bird clade. It should also be noted that at the time of the controversy over Protoavis, the evolutionary proximity between birds and maniraptoric theropods, which is now widely advocated and recognized by ornithologists, was much more controversial - in addition, most birds from the Mesozoic were discovered later. Even Chatterjee has Protoavis used to the close relationship between dinosaurs and birds support .
“With no compelling evidence of Protoavis' avian status and taxonomic validity left, it may seem a bit strange that this matter is so controversial. The author agrees with Chiappe that Protoavis has become irrelevant for the reconstruction of the bird family tree at the present time. Further finds in the Dockum group could possibly restore this strange archosaur, at least at the moment the Protoavis case has been put on record . "
literature
- Sankar Chatterjee : Skull of Protoavis and Early Evolution of Birds. In: Journal of Vertebrate Paleontology. Vol. 7, Supplement 003, 1987, ISSN 0272-4634 , p. 14A.
- Sankar Chatterjee: Cranial anatomy and relationships of a new Triassic bird from Texas. In: Philosophical Transactions of the Royal Society. Series B: Biological Sciences. Vol. 332, No. 1265, 1991, ISSN 0080-4622 , pp. 277-342, HTML abstract .
- Sankar Chatterjee: The Triassic bird Protoavis. In: Archeopteryx. Vol. 13, 1995, ISSN 0933-288X , pp. 15-31.
- Sankar Chatterjee: The Rise of Birds. 225 Million Years of Evolution. Johns Hopkins University Press, Baltimore MD 1997, ISBN 0-8018-5615-9 .
- Sankar Chatterjee: The avian status of Protoavis. In: Archeopteryx. Vol. 16, 1998, pp. 99-122.
- Sankar Chatterjee: Protoavis and the early evolution of birds. In: Palaeontographica A. Vol. 254, 1999, ISSN 0375-0442 , pp. 1-100.
- Luis M. Chiappe : The first 85 million years of avian evolution. In: Nature . Vol. 378, 1995, pp. 349-355, doi : 10.1038 / 378349a0 .
- Philip J. Currie : New information on the anatomy and relationships of Dromaeosaurus albertensis (Dinosauria: Theropoda). In: Journal of Vertebrate Paleontology. Vol. 15, No. 3, 1995, pp. 576-591.
- Lowell Dingus , Timothy Rowe : The Mistaken Extinction. Dinosaur Evolution and the Origin of Birds. WH Freeman & Company, New York NY 1998, ISBN 0-7167-2944-X .
- Alan Feduccia : The Origin and Evolution of Birds. Yale University Press, New Haven CT et al. 1996, ISBN 0-300-06460-8 (2nd edition. Ibid 1999, ISBN 0-300-07861-7 ).
- EN Kurochkin : Synopsis of Mesozoic birds and early evolution of Class Aves. In: Archeopteryx. Vol. 13, 1995, pp. 47-66.
- Ricardo N. Melchor, Silvina de Valais, Jorge F. Genise: Bird-like fossil footprints from the Late Triassic. In: Nature. Vol. 417, 2002, pp. 936-938, doi : 10.1038 / nature00818 .
- Sterling J. Nesbitt, Randall B. Irmis, William G. Parker: A critical re-evaluation of the Late Triassic dinosaur taxa of North America. In: Journal of Systematic Palaeontology. Vol. 5, No. 2, 2007, ISSN 1477-2019 , pp. 209-243, doi : 10.1017 / S1477201906001969 .
- John H. Ostrom : Protoavis, a Triassic bird? In: Archeopteryx. Vol. 5, 1987, pp. 113-114.
- John H. Ostrom: The bird in the bush. In: Nature. Vol. 353, 1991, p. 212, doi : 10.1038 / 353212a0 , digitized .
- John H. Ostrom: The questionable validity of Protoavis. In: Archeopteryx. Vol. 14, 1996, pp. 39-42.
- Gregory S. Paul : Predatory Dinosaurs of the World. A complete and illustrated guide. Simon & Schuster, New York NY et al. 1988, ISBN 0-671-61946-2 .
- Gregory S. Paul: Dinosaurs of the Air. The Evolution and Loss of Flight in Dinosaurs and Birds. Johns Hopkins University Press, Baltimore MD et al. 2002, ISBN 0-8018-6763-0 .
- Silvio Renesto: Bird-like head on a chameleon body: new specimens of the enigmatic diapsid reptile Megalancosaurus from the Late Triassic of northern Italy. In: Rivista Italiana di Paleontologia e Stratigrafia. Vol. 106, 2000, ISSN 0035-6883 , pp. 157-180, PDF online (PDF; 3.43 MB) .
- Lawrence M. Witmer : Perspectives on avian origins. In: Hans-Peter Schultze , Linda Trueb (Ed.): Origins of the Higher Groups of Tetrapods. Controversy and Consensus. Comstock, Ithaca NY 1991, ISBN 0-8014-2497-6 , pp. 427-466, online (PDF; 1.45 MB) .
- Lawrence M. Witmer: Introduction. In: Sankar Chatterjee: The Rise of Birds. 225 Million Years of Evolution. Johns Hopkins University Press, Baltimore MD 1997, ISBN 0-8018-5615-9 .
- Lawrence M. Witmer: The role of Protoavis in the debate on avian origins. In: Jacques Gauthier , Lawrence F. Gall (eds.): New perspectives on the origin and early evolution of birds. Peabody Museum of Natural History - Yale University, New Haven CT 2001, ISBN 0-912532-57-2 , pp. 537-548.
- Lawrence M. Witmer: The debate on avian ancestry: phylogeny, function, and fossils. In: Luis M. Chiappe, Lawrence M. Witmer (Eds.): Mesozoic birds. Above the heads of dinosaurs. University of California Press, Berkeley CA et al. 2002, ISBN 0-520-20094-2 , pp. 3-30.
- Zhonghe Zhou : The origin and early evolution of birds: discoveries, disputes, and perspectives from fossil evidence. In: Natural Sciences. Vol. 91, No. 10, 2004, ISSN 0028-1042 , pp. 455-471, doi : 10.1007 / s00114-004-0570-4 .
Web links
- Protoavis reconstruction ( Memento of December 17, 2008 in the Internet Archive ) (most details are disputed)
