Tarbosaurus
Reconstructed skeleton in CosmoCaixa, Barcelona
- Mongolia
- China
- Tarbosaurus bataar
Tarbosaurus (. " Terrifying lizard", from the ancient Greek: τὸ τάρβος, εος ( Tarbos ) - " terror ", " fear " and ὁ σαῦρος, σαύρου ( sauros ) - " lizard" ) is a genus theropod dinosaur from the family of Tyrannosauridae that during the late Cretaceous ( Maastrichtian ) lived in Asia.
Fossils date from all of Mongolia ( Nemegt Formation), fragmentary remains were discovered but also in parts of China. Although various species have been named, today is only one type, the type species Tarbosaurus bataar recognized. Some experts consider Tarbosaurus for an Asian representative of the North American genus Tyrannosaurus - if this is true, the genus Tarbosaurus would be invalid.
Tarbosaurus and Tyrannosaurus are considered closely related, although some paleontologists keep also derived from Mongolia Alioramus for the closest relative of Tarbosaurus. Like most known tyrannosaurids Tarbosaurus was a large bipeder carnivores with large skull and very small, two -fingered arms - the latter were with Tarbosaurus in relation to body size smaller than any other tyrannosaurids.
Tarbosaurus lived in a criss-crossed by rivers flood plain. In this habitat, he stood at the top of the food pyramid and probably hunted large dinosaurs like the Hadrosauriden Saurolophus or sauropods Nemegtosaurus. He is known by dozens of finds, including complete skulls and skeletons, allowed the scientific studies on its phylogeny, skull mechanics, and brain structure.
- 4.1 Skull mechanics
- 4.2 brain structure
Features
Tarbosaurus was one of the largest tyrannosaurids and was only slightly smaller than Tyrannosaurus. The largest known individuals were between ten and twelve feet long, and held her head up to five meters above the ground. A weight estimation of an adult individual has never been published, but it is believed that the in relation to Tarbosaurus Tyrannosaurus was slightly lighter than the latter.
The largest known Tarbosaurus skull is more than 1.3 meters long, larger than any other tyrannosaurids except Tyrannosaurus. The skull was similarly high as that of Tyrannosaurus, but especially at the back of the head is not as wide, so that the eyes were not directed directly forward - this suggests that Tarbosaurus unlike Tyrannosaurus could not see physically. In the pine sat 60-64 teeth; slightly more than Tyrannosaurus, but less than with smaller tyrannosaurid as Gorgosaurus or Alioramus. While most of the teeth in the cross section was oval, the jaw teeth of the intermediate leg ( premaxilla ) have at the front end of the upper jaw, a "D" - shaped cross section. This Heterodontie is characteristic for the whole family. The longest teeth were in the maxilla and had up to 85 mm long tooth crowns. The lower jaw was as Alioramus stabilized by a ridge on the outer surface of the angular - bone which was interlocked with the back of the dental bone -. This mechanism is absent in other tyrannosaurids, whose jaws were thus more flexible.
System
Tarbosaurus is classified within the family and within the subfamily Tyrannosauridae Tyrannosaurinae. Other members of the Tyrannosaurinae include Tyrannosaurus and the earlier Daspletosaurus in North America and probably Alioramus from Asia with a. The Tyrannosaurinae differs from the other subfamily, the Albertosaurinae, through its robust construction and its proportionally larger skulls and longer femurs.
Tarbosaurus bataar was originally described as a kind of Tyrannosaurus, which has been supported by recent studies. Other scientists prefer to separate the two taxa and to be regarded merely as a sister species. A cladistic analysis of 2003, which is based on skull characteristics, however, sees Alioramus as the closest relative of Tarbosaurus, as both genera share skull characteristics that are not found in other tyrannosaurines. This theory suggests different lineages in Asia and North America; if it can be proved, a synonymy between Tyrannosaurus and Tarbosaurus would be excluded.
Gorgosaurus
Daspletosaurus
Alioramus (?)
Tarbosaurus
Tyrannosaurus
Cladogram Tyrannosauridae by Holtz, 2004
Albertosaurus
Gorgosaurus
Daspletosaurus
Tarbosaurus
Alioramus
Tyrannosaurus
Alternative cladogram Tyrannosauridae by Currie and others 2003
History of discovery and naming
In 1946 discovered a joint Soviet -Mongolian expedition to the Gobi Desert, a large Theropodenschädel and some vertebrae. The site is located in the Mongolian Gobi Aimag Ömnö seen and heard stratigraphically to Nemegt lineup. These fossils described paleontologist Evgeny Maleev of Russian in 1955 as the type material of a new species, which he named Tyrannosaurus bataar - the Artepitheth bataar is a misspelling of the Mongolian word баатар / baatar, meaning " hero ". In the same year, described and named three other Maleev, associated with skeletal material Theropodenschädel that were discovered by the same expedition in 1948 and 1949. The first of these finds (PIN 551-2 ) called Tarbosaurus Maleev efremovi, with the new generic name Tarbosaurus from the Greek words ταρβος / Tarbos ( " frighten ", " awe " ) and σαυρος / sauros ( " lizard" ) is derived and as much as " terrifying lizard" means. The Artepitheth efremovi honors Ivan Yefremov, a Russian paleontologist and science fiction author. The other two finds ( PIN 553-1 and PIN 552-2 ) described Maleev also as a new species, but introduced her to the North American genus Gorgosaurus - each lancinator as Gorgosaurus Gorgosaurus and novojilovi. These latter three specimens were smaller than the first, bataar described as Tyrannosaurus copy.
In a publication from 1965 Anatoly Rozhdestvensky assumes that all four findings described by Maleev belong to the same species, and merely represent different stages of development. Seeing differences to Tyrannosaurus, he set the new combination on Tarbosaurus bataar, which includes both the findings described in 1955 as well as newer material. Later authors, including Maleev himself, agreed with Roschdestwenskis analysis, although others used the name Tarbosaurus Tarbosaurus bataar efremovi instead. The American paleontologist Kenneth Carpenter examined the material again in 1992 and concluded it belonged to the genus Tyrannosaurus, as originally adopted by Maleev. Carpenter ordered all known Tarbosaurus discoveries of Tyrannosaurus way to bataar, except for the remains that Maleev Gorgosaurus novojilovi called - for this find, he described the new genus Maleevosaurus novojilovi. George Olshevsky (1995 ) introduced the new genus name Jenghizkhan (after Genghis Khan) for Tyrannosaurus bataar and held simultaneously Tarbosaurus efremovi and Maleevosaurus novojilovi valid, giving a total of three different contemporary tyrannosaurid genera from the Nemegt lineup. A study published in 1999 study classified as a juvenile Tarbosaurus Maleevosaurus. All publications since 1999 recognize only a single species, which is called either Tarbosaurus or Tyrannosaurus bataar bataar.
After the Russian-Mongolian expeditions in the 1940s found from 1963 to 1971 Polish- Mongolian expeditions to the Gobi desert place, and discovered many new fossils from the Nemegt lineup, including new Tarbosaurus discoveries. Expeditions of Japanese and Mongolian scientists between 1993 and 1998 as well as private, hosted by the American paleontologist Phillip Currie expeditions around the turn of the 21st century, discovered another Tarbosaurus material. So far, over 30 finds are known, including more than 15 skulls and several complete Postkranialskelette (residual skeletons ).
Possible synonyms
Chinese paleontologists discovered a partial skeleton with skull of a small theropod ( IVPP V4878 ) in the autonomous Chinese region of Xinjiang in the mid- 1960s. This native of the Subashi lineup Fund was described in 1977 by Dong Zhiming as a new genus and species, Shanshanosaurus huoyanshanensis. Gregory Paul (1988 ) saw a Shanshanosaurus tyrannosaurids and wrote him the genus Aublysodon to that date, however, applies dubium as a noun and is therefore no longer used. Later, Dong and Currie examined the Fund again and considered it as a juvenile specimen of a larger tyrannosaurid species, but without the Fund attributable to a particular type. These researchers noted, however, that Tarbosaurus is a possibility. Over the years, other Chinese sites more tyrannosaurid teeth and fragmentary remains brought to light, some of which have been designated. Periculosis Albertosaurus, Tyrannosaurus luanchuanensis, Tyrannosaurus turpanensis and Chingkankousaurus fragilis are often considered synonyms of Tarbosaurus.
Alioramus, who was named by Kurzanov in 1976, is another tyrannosaurid genus from slightly older sediments of Mongolia. Some analyzes suggest that Alioramus was very closely related to Tarbosaurus. The only specimen found was described as adult individual; However, the long, low skull is characteristic of juvenile tyrannosaurids. Currie speculated that Alioramus might have been a juvenile Tarbosaurus, but noticed that the significantly larger number of teeth and the number of bony bumps on the skull top speak against this hypothesis.
Paleobiology
Like some other tyrannosaurids Tarbosaurus is also by a relatively large and well-preserved finds known - actually comes a quarter of all fossils from the Nemegt formation of Tarbosaurus. Although Tarbosaurus has not been studied as intensively as the North American tyrannosaurids, the available material allows conclusions about the biology of this animal.
Skull mechanics
The skull of Tarbosaurus was described in 2003 by Hurum and Sabath first full. Scientists conducted on differences between Tarbosaurus and the North American tyrannosaurids, related in large part to the transfer of loads during a bite. If the upper jaw biting on an object, the force is transmitted through the maxilla ( the primary tooth-bearing bones in the upper jaw ) to the surrounding cranial bones. In North American tyrannosaurids the power of the maxilla moves in the fused, paired nasal bone ( nasal ) to the skull top that on the back by bony struts closely with the paired lacrimal bone ( lacrimal ) was connected. These struts joined together these bones, which suggests that the force was further transferred from the nose to the lacrimal bone.
Tarbosaurus lacked these struts, and the connection between the nasal bone and lacrimal bone was weak. Instead, a rear-facing protrusion of the maxilla in Tarbosaurus was very strong, which fits into a formed by the lacrimal bone trough. In North American tyrannosaurids, this projection was only a thin, bony plate. The big advantage suggests that the force was transmitted directly from Tarbosaurus from the maxilla to the lacrimal bone. The lacrimal bone was also closely anchored to the prefrontal ( frontal ) and Präfrontalknochen; the well-developed connections between maxilla, lacrimal, prefrontal and prefrontal made the entire upper jaw rigid.
Another significant difference between Tarbosaurus and its North American relatives was the rigid lower jaw. While many theropods, including North American tyrannosaurids had a certain degree of flexibility between the bones of the lower jaw, Tarbosaurus had a locking mechanism: So sat on the Angularknochen a comb, which was hooked to a square process on the back of the lower jaw.
Some researchers have hypothesized that rigid skull of Tarbosaurus may have been an adaptation to hunting the big Titanosaurier that were found in the Nemegt lineup, but often missing in North America in the late Cretaceous. The differences in skull mechanics also allow conclusions about the relationships of the tyrannosaurids: Tarbosaurus -like connections between skull bones are also from the Mongol Alioramus known, suggesting that this species, and not Tyrannosaurus, is the closest relative of Tarbosaurus was. Tarbosaurus and Tyrannosaurus similarities between could also be due to their huge size and have evolved independently through convergent evolution.
Brain structure
In a Tarbosaurus Skull (PIN 553-1 ), which was discovered by the Soviet- Mongolian expedition in 1948 and originally called Gorgosaurus lancinator, was preserved the skull - this allows casts of the brain. Maleev been made based on a plaster cast of preliminary observations of the shape of a Tarbosaurus - brain; However, a recent cast polyurethane rubber allowed a more detailed study of the brain structure and function.
Another study examined the brain structure of Tyrannosaurus rex, which was very similar to Tarbosaurus - differences are only in the positions of some nerves such as the trigeminal nerve and the accessory nerve. The brains of tyrannosaurids were similar to those of extant crocodiles and other reptiles more than those of birds and were relatively small; so the brain volume of a twelve -meter long Tarbosaurus is only 184 cubic centimeters. Leave large olfactory bulb and nervus terminalis and well-developed olfactory nerve ( olfactory nerve ) suggest that Tarbosaurus had a good sense of smell, as was the case with Tyrannosaurus. The Jacobson organ was well developed; an olfactory organ, which mainly serves many animals today the perception of pheromones. This might suggest that Tarbosaurus had a complex mating behavior. The vestibulocochlear nerve was also large and is evidence of a marked auditory perception as well as a good sense of coordination and balance. In contrast, the nerves and the brain structures that were responsible for the sense of sight were smaller and underdeveloped: The midbrain roof, which is responsible for reptiles for the processing of visual stimuli was in Tarbosaurus very small; as well as the optic nerve and the oculomotor nerve that controls eye movements. Unlike Tyrannosaurus, which had forward facing eyes that allowed a spatial vision, Tarbosaurus had a thinner skulls with laterally directed eyes, as was typical of other tyrannosaurids. All this suggests that Tarbosaurus left more to its smell and hearing than on his sense of sight.
Paleoecology
The vast majority of Tarbosaurus - Fossililen comes from the Nemegt Formation of southern Mongolia. The age of this geologic formation was never determined radiometrically, documented in the fossil record fauna can, however, close to a period of deposition during the Maastrichtian ( 72-66 million years ago ), the last stage of the Cretaceous period. The Subashi lineup containing the Shanshanosaurus remnants, was also dated to the Maastrichtian. In the sediments of the Nemegt lineup conceal the remains of flood plains, large rivers and paleosols, suggesting a humid climate with periodic droughts - in contrast to the semi-arid environments of the underlying Barun Goyot lineup and Djadochta lineup. The vertebrate fauna in the water consisted of fish, turtles and crocodiles as Shamosuchus, which was represented by several species and specializes in the cracking of shells. Mammalian fossils are extremely rare in the Nemegt lineup, but many birds are known as the Enantiornithe Judinornis, the Hesperornithiforme Gurilynia and Anseriforme Teviornis. Scientists also described many dinosaur species from the Nemegt lineup, including ankylosauruses as Tarchia and Pachycephalosauriern as Homalocephale and Prenocephale. As by far the largest predators of time chasing adult Tarbosaurus likely large hadrosaur as Saurolophus and Barsboldia or sauropods like Nemegtosaurus and Opisthocoelicaudia. Smaller theropods of the formation close troodontids ( Borogovia, Tochisaurus, Saurornithoides ) Oviraptorosaurier ( Elmisaurus, Nemegtomaia, Rinchenia ) or Bagaraatan, which is sometimes classified as basal Tyrannosauroide, with a. Other theropods, such as the gigantic Therizinosaurus were perhaps herbivor while Ornithomimosaurier as Anserimimus, Gallimimus and Deinocheirus might have been omnivores. Since mid-sized predators are missing, juvenile Tarbosaurus may have filled this gap.
Others
The skeleton of Tarbosaurus is bataar issued at the presidential palace of East Timor. It was excavated by a team of Australia's Monash University in Mongolia and serves as a loan now in East Timor as a demonstration for school children.