Tyrannosauroidea

Skeletal reconstruction of Albertosaurus at the Royal Tyrrell Museum in Alberta

• North America
• Europe
• Asia

The Tyrannosauroidea is a superfamily of Coelurosaurier ( Coelurosauria ) within the theropod dinosaurs. It includes the Tyrannosauridae, which include for instance the famous Tyrannosaurus rex belongs, as well as the basal, ie standing at the beginning of the series developed species. Tyrannosauroideen lived on the northern supercontinent Laurasia and first appeared in the Middle Jurassic period about 168 million years ago. In the Cretaceous, they were the dominant large predators in the northern hemisphere. Their fossils have been discovered in North America, Europe and Asia.

Tyrannosauroiden were like most theropod bipedal carnivores. The group is characterized by numerous shared derived characteristics ( synapomorphies ) that are found especially in the skull and pelvic bones. Early in their evolution were Tyrannosauroiden small predators with long, three -fingered arms. Types of Upper Cretaceous were much larger and included some of the largest terrestrial carnivore with one, that have ever existed - but most of these late species had proportionally small arms with only two fingers. Primitive feathers are of Dilong known, an early Tyrannosauroiden from China, as well as Yutyrannus and were with other Tyrannosauroiden perhaps also available. Many types wore flashy bone combs in different forms, perhaps he used the display.

• 4.1 springs
• 4.2 head combs

Features

Height varied considerably between individual species, but in the course of evolution, the group was getting bigger. Early Tyrannosauroideen were relatively small animals - so reasonably adult specimens of Dilong 1.6 meters and guanlong three meters in length. Genera of the Cretaceous were larger; as a not yet mature Eotyrannus over four meters and a not yet fully mature Appalachiosaurus was more than six feet long. The Upper Cretaceous tyrannosaurids were again at some gigantic proportions. Albertosaurus and Gorgosaurus were both about nine feet long, and Tyrannosaurus was more than twelve feet in length, and perhaps more than 6400 kilograms, the largest known genus.

The skull earlier Tyrannosauroideen were long, built low and light and are thus similar to those of other Coelurosaurier, while later forms had significantly higher and more massive skull. Despite these differences, certain skull characteristics ( synapomorphies ) can be found in all known Tyrannosauroideen: So the premaxillary bone ( premaxilla ) was very high, which had a blunt snout result - a feature that has convergently developed in the Abelisauriden. The paired nasal bone was fused, slightly arched top and on the top usually very rough, often bark-like structure. Between the teeth of the jaw bone in the front part of the upper jaw were smaller and shaped differently than the remaining teeth, and had a "D" -shaped cross -section. The lower jaw of all Tyrannosauroideen except guanlong had a pronounced crest on the Surangulare which extended laterally just below the jaw joint.

Tyrannosauroideen had like most other theropods "S" - shaped bent necks and long tails. Early species had three -fingered, long arms, the 60 percent of the length of the hind legs reached at guanlong. The long arms were characteristic of the group to at least the Early Cretaceous, as Eotyrannus shows, but at Appalachiosaurus they have not been preserved. The arms later Tyrannosauroideen were significantly smaller - the most extreme example is Tarbosaurus from Mongolia, the upper arm bone (humerus ) reached only a quarter of the length of the thigh bone (femur). The third finger has also regressed in the course of evolution: While he was not reduced in the basal guanlong, it was considerably smaller than the other two fingers already at Dilong. Eotyrannus still had three functional fingers on each hand; However tyrannosaurids had only two fingers, although the rudiments of a third finger were detected in some specimens. As with most other Coelurosauriern the second finger was the greatest.

Characteristic features in the pelvic bones include a notch at the bottom of the ilium ( ilium ), extended significantly limited vertical ridge on the ilium, extending from the hip joint socket ( acetabulum ) upwards, and the enlarged end of the pubis ( pubic bone ) with a, the extended "T" -shaped on both sides, more than half as long as was the actual shaft of the pubic bone. These features are found in all known Tyrannosauroideen, including the basal genera guanlong and Dilong. The pubic bone is unknown in Aviatyrannis and Stokesosaurus; however, show both classes for Tyrannosauroideen typical features in the ilium. The hind legs of all Tyrannosauroideen had like most theropods four toes, although the first toe ( hallux ) did not touch the ground. The hind legs of the Tyrannosauroideen were in relation to body size longer than in almost all other theropods and show proportions that are characteristic of fast moving animals; so the shinbone ( tibia bone ) and the metatarsal bones were extended. These proportions were even in the largest known specimen of Tyrannosaurus, although such animals perhaps could not run. The third metatarsal of tyrannosaurids was pushed up between the other two metatarsal - a structure that is known as Arctometatarsus. The Arctometatarsus was also detected in Appalachiosaurus, but it is not clear whether he was also present at Eotyrannus or Dryptosaurus. This structure is found in Ornithomimiden, troodontids and Caenagnathiden, but was at basal Tyrannosauroideen as Dilong not present, suggesting convergent evolution.

System

Tyrannosaurus was named together with the family of Henry Fairfield Osborn Tyrannosauridae in 1905. The name derives from the ancient Greek words τύραννος / tyrannos ( " tyrant " ) and σαῦρος / sauros ( " lizard" ) from. The name of the superfamily Tyrannosauroidea published for the first time, the British paleontologist Alick Walker in 1964. Oidea The ending- which is usually used for About families in the animal kingdom, is from the ancient Greek εἶδος / eidos ("Form " ) is derived.

Scientists understood the Tyrannosauroidea mostly as a taxon that includes the tyrannosaurids and their immediate ancestors. Since phylogenetic systematics was introduced in paleontology, but the group received precise definitions. The first was set up by Paul Sereno in 1998 and sees the Tyrannosauroidea as a taxon that includes with all species that were more closely related to Tyrannosaurus rex as with neornithen birds. To describe the group even more exclusive, Thomas Holtz defined it new in 2004 to include all species with that Tyrannosaurus rex with a velox closer with Ornithomimus, Deinonychus antirrhopus Allosaurus fragilis or were related. Sereno published in 2005 a new definition, belong after all species of the Tyrannosauroidae closer to Tyrannosaurus rex as with Ornithomimus edmontonicus, Velociraptor and Troodon formosus mongoliensis were related.

Classification

Superfamily Tyrannosauroidea

• ? Iliosuchus ( Middle Jurassic, England)
• Aviatyrannis ( Upper Jurassic, Portugal)
• Stokesosaurus ( Upper Jurassic, Western USA )
• Dilong ( Lower Cretaceous, eastern China)
• Eotyrannus ( Lower Cretaceous, England)
• Raptorex ( Lower Cretaceous, eastern China)
• Xiongguanlong ( Lower Cretaceous, China)
• Yutyrannus ( Lower Cretaceous, China)
• ? Bagaraatan ( Upper Cretaceous, Mongolia)
• Dryptosaurus ( Upper Cretaceous, eastern United States)
• Alectrosaurus ( Upper Cretaceous, Mongolia)
• Appalachiosaurus ( Upper Cretaceous, eastern United States)
• ? Labocania ( Upper Cretaceous, western Mexico)
• Bistahieversor ( Upper Cretaceous, western United States)
• Family Proceratosauridae Kileskus ( Middle Jurassic, central Russia)
• Proceratosaurus ( Middle Jurassic, England)
• Guanlong ( Upper Jurassic, western China)
• Sinotyrannus ( Lower Cretaceous, eastern China)

• Albertosaurus ( Upper Cretaceous, western United States)
• ? Alioramus ( Upper Cretaceous, Mongolia)
• Daspletosaurus ( Upper Cretaceous, western United States)
• Gorgosaurus ( Upper Cretaceous, western United States)
• Lythronax ( Upper Cretaceous, western North America )
• Tarbosaurus ( Upper Cretaceous, Mongolia)
• Teratophoneus ( Upper Cretaceous, United States)
• Tyrannosaurus ( Upper Cretaceous, western United States)
• Zhuchengtyrannus ( Upper Cretaceous, China)

Phylogenetics

In the 20th century tyrannosaurids were usually representing the Carnosauria which which included almost all the major theropods with after damaligem point of view. Within this group, the Allosauriden were often considered the ancestors of the tyrannosaurids. In the early 1990s began cladistic analyzes to classify the Tyrannosauridae within the Coelurosauria with first guesses were already expressed in the 1920s. Tyrannosaurids are now considered universally as a great Coelurosaurier.

In 1994, Holtz grouped the Tyrannosauroideen together with the Elmisauriden, the Ornithomimosauriern and troodontids in a new group within the Coelurosauria, which he called Arctometatarsalia. The group is based on the Arctometatarsus, a structure in the metatarsal bone, wherein the second metatarsal bones viewed from the front is covered by the remaining two metatarsal part. However Basal Tyrannosauroideen as Dilong showed no Arctometatarsus, which suggests that this feature in different groups several times independently ( convergent ) has developed. Therefore, the group Arctometatarsalia was discarded and not used by most paleontologists, the Tyrannosauroidea is now usually classified as a basal group of Coelurosauria outside the Maniraptoriformes. A new analysis concludes that the family Coeluridae could have been the sister taxon of Tyrannosauroidea.

The most original Tyrannosauroide known of complete skeletal material, guanlong is. Other early genera close Stokesosaurus and Aviatyrannis with one, but only far less complete material known. The better-known Dilong is a bit more modern than guanlong and Stokesosaurus. Dryptosaurus was long classified as difficult, but is now run as a basal Tyrannosauroide, which was a bit more original than Eotyrannus and Appalachiosaurus. Alectrosaurus, a little-known genus from Mongolia, is definitely a Tyrannosauroide, but its exact relationships are unclear. Other taxa have been proposed by some authors as a possible Tyrannosauroiden, including Bagaraatan, Labocania and a genus that was incorrectly assigned to the Chilantaisaurus, " C." maortuensis. Siamotyrannus from the Lower Cretaceous of Thailand was originally described as Tyrannosauride earlier, but is now regarded as a member of Carnosauria. Iliosuchus shows a vertical ridge on the ilium, which is a feature of Tyrannosauroidea. This genus may therefore actually be the earliest known representatives of this superfamily, which can be confirmed only by further bone finds.

Dissemination

The earliest known Tyrannosauroideen lived in the Middle Jurassic and close guanlong of northwestern China, Stokesosaurus from the western U.S. and Aviatyrannis from Portugal with a. Some fossils that are currently attributed to the Stokesosaurus, perhaps among Aviatyrannis - the Dinosaurierfaunen from Portugal and North America at this time is actually very similar. If Iliosuchus on the Middle Jurassic of England actually was a Tyrannosauroide, he would be the earliest known genus; this could indicate that the superfamily Tyrannosauroidea in Europe had its origin.

Tyrannosauroideen the Lower Cretaceous were also found in all three northern continents. Eotyrannus from England and Dilong from northeastern China are the only two named genera from this time; are further known teeth of the premaxillary bone from the Cedar Mountain Formation in Utah ( United States) and from the Tetori Group in Japan. " Chilantaisaurus " maortuensis from the Dashuigou Formation of Inner Mongolia in China is sometimes also considered to be an early Tyrannosauroide the Lower Cretaceous.

In Europe Tyrannosauroideen have disappeared from the fossil record since the middle Cretaceous, suggesting a local extinction on this continent. Teeth and possible body fossils from the middle Cretaceous are known from the North American lineup Dakota, as well as formations in Kazakhstan, Tajikistan and Uzbekistan. The first undoubted remains of tyrannosaurids are from the Campanian ( Late Cretaceous ) of North America and Asia. This family is divided into two subfamilies, the albertosaurines were detected only in North America, the tyrannosaurines but were discovered on both continents. Fossils from tyrannosaurids have also been discovered in Alaska, which was perhaps connected with a land bridge with Asia, via the were able to share the faunas of North America and Asia. The Tyrannosauroideen Alectrosaurus and perhaps Bagaraatan be classified outside the Tyrannosauridae, lived with them in Asia but at the same time, while they were absent in North America. The eastern North America has been isolated since the center chalk by an arm of the sea, the Western Interior Seaway, from the western part of the continent. Since tyrannosaurids lacked in the eastern part of the continent, it is believed that this family originated only after the arm of the sea had divided the country. This allowed basal Tyrannosauroideen as Dryptosaurus and Appalachiosaurus in eastern North America to survive to the end of the Cretaceous.

Paleobiology

Spring

Long fibrous structures have been preserved along with the skeletons of numerous Coelurosaurier that originate from the Lower Cretaceous Yixian Formation and other formations from Liaoning (China). These structures are interpreted usually as " proto- feathers", homologous to the branched feathers of modern birds, although other hypotheses have been proposed. A process described in 2004 skeleton of Dilong is the first known example of proto- feathers in Tyrannosauroideen. Like the down of modern birds were verästelt known of Proto Dilong feathers, but it was not to contour feathers. Maybe they served the thermal insulation.

The proto- feathers were found in basal Tyrannosauroideen, is not surprising, since springs are considered to be a characteristic feature of Coelurosaurier. They are found in other basal genera such as Sinosauropteryx as well as more modern genres. However, rare skin impressions of large tyrannosaurids show no evidence of feathers, but instead a scaly skin. It is possible that proto feathers were present on parts of the body that have not been passed on by skin marks. Alternatively, the proto- feathers may have been lost in large tyrannosaurids, as the small surface - to-volume ratio of these animals makes thermal insulation unnecessary - similar to today's large mammals such as elephants. An exception is Yutyrannus, wherein up to 20 centimeters long filaments were found to be interpreted as springs.

Head combs

Bone combs were found on the skulls of many theropods, including many Tyrannosauroideen. The most spectacular example is guanlong, in which the paired nasal bone supports a single, large comb, which ran on the center line of the skull from snout to rear. The ridge was crossed by large openings, which reduced his weight. Less conspicuous were the head ornaments of Dilong, which consisted of two low, parallel ridges that ran on each side of the skull and were supported by nasal bone and lacrimal bone. The combs were directly behind the nostrils curved inwards, making a "Y" -shaped structure resulted. The fused paired nasal bones of tyrannosaurids was often structured very rough. Alioramus, a possible Tyrannosauride from Mongolia, showed a single row of five prominent bony bumps on the nose; a similar series with much smaller bumps is known of Appalachiosaurus as well as some finds of Daspletosaurus, Albertosaurus and Tarbosaurus. The person sitting on the lacrimal horn is absent in Tarbosaurus and Tyrannosaurus in which instead a crescent-shaped hood had to post orbital bones behind each eye. The head crests of Tyrannosauroideen were probably the display - perhaps for species recognition or courtship.