Amurosaurus
| Amurosaurus | ||||||||||||
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Live reconstruction of Amurosaurus |
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| Temporal occurrence | ||||||||||||
| Upper Cretaceous (late Maastrichtian ) | ||||||||||||
| 69.9 to 66 million years | ||||||||||||
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| Scientific name | ||||||||||||
| Amurosaurus | ||||||||||||
| Bolotsky & Kurzanov , 1991 | ||||||||||||
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Amurosaurus ("lizard from the Amur region") is a dinosaur from the family of Hadrosauridae (duck-billed dinosaurs), which belongs to the Ornithischia (bird-pelvis dinosaurs).
The remains - an incomplete skull as well as other, postcranial (non-skull) material - come from a single bone bed from the Amur region in eastern Russia , which can be assigned to the Upper Cretaceous (late Maastrichtian ) . It is a basal lambeosaurine up to eight meters long , which like its relatives was a herbivore (herbivore) and probably walked four-legged as well as two-legged. The only known species of this genus is Amurosaurus riabinini .
Site and history
The Amurosaurus find
In 1984, on the outskirts of the city of Blagoveschensk , on the Russian side of the Amur River, a large bonebed was discovered which in 1991 had already released several hundred bones in a 200 square meter excavation area. Much of the bones belonged to lambeosaurine dinosaurs, although isolated theropod teeth - and bite marks on the lambeosaurine bones - have also been discovered, suggesting predators or scavengers. A small part of the bones (connected left maxilla (upper jawbone) and lower jawbone ; holotype AEHM 1/12) was briefly described by Bolotsky and Kurzanov in 1991 as Amurosaurus riabinini . The Artepitheth riabinini honors the paleontologist Anatoly Riabinin , who led the first Russian dinosaur expeditions in this region (see below). The remaining bones, however, mostly belonging to juvenile Amurosaurus , have not been described. In the following years , Amurosaurus received little attention from paleontologists , until in 2004 a more detailed description of all bones discovered so far (Godefroit, Bolotsky and Itterbeeck) was given.
From a geological point of view, the layers of the site belong to the Udurchukan Formation , which forms the lower part of the Tsagayan Group . The fossil-bearing sediments consist of greenish, granulated clay . At that time, these sediments lay together with the bones in a floodplain or a river. The unconnected bones are well preserved - even fragile skull bones are present - and not sorted by size. This suggests that the bones were only transported a short distance by the water.
Further finds from the Amur region
In the vicinity of the Amur River - which forms the border between Russia and the People's Republic of China for a long stretch - dinosaur fossils have been discovered since 1902 - mostly hadrosaurid bones. The first known find consists of isolated bones found near the village of Jiayin on the Chinese side. In 1916 and 1970, excavations carried out by the Russian Geological Committee in the Jiayin area uncovered additional bones. Anatoly Riabinin assigned them to the Hadrosauridae and described two new species, Trachodon amurense and Saurolophus krystofovici , which today are classified as Nomia Dubia (doubtful) due to the very fragmentary remains . Godefroit, et al. (2000, 2001) described another species from Jiayin: Charonosaurus jiayinensis . Dinosaur fossils from the Russian side were first discovered in 1957. A more recent discovery in the Russian Amur region is, in addition to the Amurosaurus bone bed near Blagoveschensk, a site near Kundur . Here, along with other bones, an almost complete hadrosaurid skeleton with a large head crest was found, which was described in 2003 as Olorotitan arharensis (Godefroit, Bolotsky and Alifanov).
Description and demarcation from other species
The skeleton is almost completely known, which makes Amurosaurus one of the best-known Russian dinosaurs. However, the top of the skull as well as the "duck's bill" (premaxillary and pre-dentary) are missing, and a bone crest, as it occurs in other lambeosaurins in sometimes bizarre forms, was not found. However, the skull bones are built in such a way that they would support a comb - so it can be assumed that this animal also wore a comb. In reconstructions, Amurosaurus is usually shown with a slightly smaller bone crest.
The skeleton differs from that of other lambeosaurins in many autapomorphies - including z. B. the elongated and S-shaped humerus ( ulna and radius ). Of the other two, known from the Amur region Lambeosaurinen from the Maastrichtian, charonosaurus ( Yuliangze lineup ) and olorotitan (Udurchukan formation), can be amurosaurus delineate clear: different 14 as significant by 22 major skeletal features can between amurosaurus and charonosaurus viewed become. The differences between Amurosaurus and Olorotitan are smaller (only six features), but this is attributed to the fact that different parts of the skull have been preserved in each case.
Systematics
Amurosaurus is classified within the subfamily Lambeosaurinae, which together with the Hadrosaurinae forms the family Hadrosauridae. Within the Lambeosaurinae there are two subgroups - the Parasaurolophini ( Charonosaurus and Parasaurolophus ) and the Lambeosaurini ( Corythosaurus , Hypacrosaurus , Olorotitan , Lambeosaurus and Nipponosaurus ). Jaxartosaurus and Tsintaosaurus are considered to be more basal taxa due to some more primitive skull features. Also amurosaurus is one of the more basal species, but is more modern than jaxartosaurus and Tsintaosaurus and is the two subgroups as Schwestertaxon opposite. The fact that all basal lambeosaurinae are from Asia led to the theory that this subfamily originated in Asia and later spread to North America as well.
| Hadrosauridae |
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literature
- Pascal Godefroit, Yuri L. Bolotsky, Jimmy Van Itterbeeck: The lambeosaurine dinosaur Amurosaurus riabinini, from the Maastrichtian of Far Eastern Russia. In: Acta Palaeontologica Polonica. Vol. 49, No. 4, 2004, ISSN 0567-7920 , pp. 585-618, online .
Individual evidence
- ^ A b Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, p. 308, ISBN 978-0-691-13720-9 , online .
