Siamotyran [1] ( lat. Siamotyrannus ) is a genus of theropod dinosaurs from the Metriacanthosauridae family, whose fossils are found in the layers of the Barremian - Aptian tiers in Thailand . The genus includes the type and only species Siamotyrannus isanensis [2] .
| † Siamothiran |
Reconstruction of the pelvic bones and initial caudal vertebrae |
| Scientific classification |
|---|
| No rank : | Bilateral symmetrical |
| Infraclass : | Archosauromorphs |
| No rank : | Archosauriformes |
| Superfamily : | † Allosaurus |
| Family: | † Metriacanthosauridae |
| Subfamily : | † Metriacanthosaurinae |
|
| International scientific name |
|---|
Siamotyrannus Buffetaut et al. 1996 |
| Single view |
|---|
† Siamotyrannus isanensis
Buffetaut et al. 1996 |
Geochronology129.4-113.0 Ma | million years | Period | Era | Aeon |
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| 2,588 | Even | | | Ka | F
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e
R
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th | | 23.03 | Neogene | | 66.0 | Paleogen | | 145.5 | a piece of chalk | M
e
s
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s
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th | | 199.6 | Yura | | 251 | Triassic | | 299 | Permian | P
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l
e
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s
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th | | 359.2 | Carbon | | 416 | Devonian | | 443.7 | Silur | | 488.3 | Ordovician | | 542 | Cambrian | | 4570 | Precambrian |
◄ Nowadays◄ Cretaceous-Paleogene extinction◄ Triassic extinction◄ Mass Permian Extinction◄ Devonian extinction◄ Ordovician-Silurian extinction◄ Cambrian explosion |
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In 1993, a certain Somchai Traimwichanon discovered parts of the skeleton of a large theropod in the section of Phu Wiang 9 in Khon Kaen . In 1996, , and Haiyan Tong named and described the type species Siamotyrannus isanensis . The generic name is derived from the obsolete name of Thailand - Siam , with the addition of Greek. tyrannus - tyrant with a reference to the alleged relationship to the tyrannosaurid family. The species name is derived from the Thai word Isan - the north-eastern part of the country, with a reference to the place of find - northeast of Thailand [3] .
The holotype PW9-1 was discovered in the formation , which is dated to the Barremian - Aptian tiers of the Cretaceous system ( 129.4-1133 million years ago). It includes the left half of the pelvis , five posterior dorsal vertebrae, sacrum with five sacral vertebrae and 13 proximal caudal vertebrae [3] . In 1998, the tibia and several teeth were attributed to the species [4] .
Siamotiran was a large theropod. E. Buffeto estimated its length at 6.5 meters with an average size of a tyrannosaurus of 12 meters. In 2010, estimated the size of the animal at 6 meters and its weight at half a ton [5] .
The authors of the original description identified several autapomorphies - unique derived features that are used to diagnose a taxon : the presence of two vertical ridges on the ilium ; 2 and 3 sacral vertebrae are transversely flattened [3] .
As the name implies, it was initially assumed that the dinosaur belongs to tyrannosauroids or even tyrannosaurids [3] , although due to the lack of some primary tyrannosauroid synapomorphies that determine the clade, its position in it was not initially reliable [6] . As a result of some phylogenetic analyzes, siamothyran was classified as a primitive carnosaurus rather than a basal tyrannosauroid, while the fossil shows some features inherent in allosaurids or synraptorides [7] . In 2012, a group of paleontologists led by Matthew Carrano restored the siamothyran as a representative of the subfamily Metriacanthosaurinae [8] .
- ↑ Fossil vertebrates of Russia and neighboring countries. Fossil reptiles and birds. Part 2 / Kurochkin E.N. , Lopatin A.V. - M .: GEOS, 2012. - T. 2. - P. 186. - 419 (154 fig., 26 phototables.) P. - ISBN 978-5-89118-594-4 .
- ↑ Siamotyrannus (English) information on the Paleobiology Database website. (Retrieved November 30, 2018)
- ↑ 1 2 3 4 Buffetaut E., Suteethorn V., Tong H. The earliest known tyrannosaur from the Lower Cretaceous of Thailand (Eng.) // Nature . - 1996. - Vol. 381 , no. 6584 . - P. 689-691 . - DOI : 10.1038 / 381689a0 .
- ↑ Buffetaut E., Suteethorn V. Early Cretaceous dinosaurs from Thailand and their bearing on the early evolution and biogeographical history of some groups of Cretaceous dinosaurs // Lower and Middle Cretaceous Terrestrial Ecosystems. New Mexico Museum of Natural History Bulletin 14 / Lucas, Kirkland, Estep. - 1998. - P. 205-210.
- ↑ Paul GS The Princeton Field Guide to Dinosaurs. - Princeton: Princeton University Press, 2010 .-- P. 91.
- ↑ Rauhut OWM Special Papers in Palaeontology: The Interrelationships and Evolution of Basal Theropod Dinosaurs. No. 69. The Palaeontological Association: 2003
- ↑ Holtz Th. R. et al. Basal Tetanurae // The Dinosauria / Weishampel DB, Dodson, P., Osmólska H. .. - Berkeley: University of California Press, 2004. - Vol. 2nd. - P. 101. - ISBN 0-520-24209-2 .
- ↑ Carrano MT, Benson RBJ, Sampson SD The phylogeny of Tetanurae (Dinosauria: Theropoda) (Eng.) // Journal of Systematic Palaeontology. - 2012. - Vol. 10 , no. 2 . - P. 211-300 . - DOI : 10.1080 / 14772019.2011.630927 .
