Tyrannosauroidea

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Tyrannosauroids
Temporal range:
Middle JurassicLate Cretaceous, 166–66  Ma
Tyrannosauroidea Infobox Panoply.png
Six tyrannosauroids (top left to bottom right): Tyrannosaurus , Dilong , Alioramus (background) with Guanlong (foreground), Gorgosaurus , and a pair of Yutyrannus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Coelurosauria
Clade: Tyrannoraptora
Superfamily: Tyrannosauroidea
Osborn, 1906 (vide Walker, 1964)
Type species
Tyrannosaurus rex
Osborn, 1905
Subgroups
Possible tyrannosauroids

Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period. By the end of the Cretaceous Period, tyrannosauroids were the dominant large predators in the Northern Hemisphere, culminating in the gigantic Tyrannosaurus . Fossils of tyrannosauroids have been recovered on what are now the continents of North America, Europe and Asia, with fragmentary remains possibly attributable to tyrannosaurs also known from South America and Australia.

Contents

Tyrannosauroids were bipedal carnivores, as were most theropods, and were characterized by numerous skeletal features, especially of the skull and pelvis. Early in their existence, tyrannosauroids were small predators with long, three-fingered forelimbs. Late Cretaceous genera became much larger, including some of the largest land-based predators ever to exist, but most of these later genera had proportionately small forelimbs with only two digits. Primitive feathers have been identified in fossils of two species and may have been present in other tyrannosauroids as well. Prominent bony crests in a variety of shapes and sizes on the skulls of many tyrannosauroids may have served display functions.

Description

Size of some small genera, compared to a human. Tyrannosauroidea size 01.jpg
Size of some small genera, compared to a human.

Tyrannosauroids varied widely in size, although there was a general trend towards increasing size over time. Early tyrannosauroids were small animals. [1] One specimen of Dilong, almost fully grown, measured 1.6 meters (5.2 feet) in length, [2] and a fully grown Guanlong measured 3 meters (9.8 feet) long. [3] Teeth from Lower Cretaceous rocks (140 to 136 million years old) of Hyogo, Japan, appear to have come from an approximately 5 metres (16 ft) long animal, possibly indicating an early size increase in the lineage. [4] An immature Eotyrannus was over 4 meters (13 feet) in length, [5] and a subadult Appalachiosaurus was estimated at more than 6 meters (20 feet) long, [1] indicating that both genera reached larger sizes. The Late Cretaceous tyrannosaurids ranged from the 9 meters (30 feet) Albertosaurus and Gorgosaurus to Tyrannosaurus , which exceeded 12 meters (39 feet) in length and may have weighed more than 6,400  kilograms (7  short tons). [1] A 2010 review of the literature concluded that tyrannosaurs were "small- to mid-sized" for their first 80 million years but were "some of the largest terrestrial carnivores to ever live" in their last 20 million years. [6] [7]

Skull and neck of Daspletosaurus, from the Field Museum of Natural History in Chicago. Daspletosaurus FMNH.jpg
Skull and neck of Daspletosaurus , from the Field Museum of Natural History in Chicago.

Skulls of early tyrannosauroids were long, low and lightly constructed, similar to other coelurosaurs, while later forms had taller and more massive skulls. Despite the differences in form, certain skull features are found in all known tyrannosauroids. The premaxillary bone is very tall, blunting the front of the snout, a feature which evolved convergently in abelisaurids. The nasal bones are characteristically fused, arched slightly upwards and often very roughly textured on their upper surface. The premaxillary teeth at the front of the upper jaw are shaped differently from the rest of the teeth, smaller in size and with a D-shaped cross section. In the lower jaw, a prominent ridge on the surangular bone extends sideways from just below the jaw joint, except in the basal Guanlong. [1] [2] [3]

Tyrannosauroids had S-shaped necks and long tails, as did most other theropods. Early genera had long forelimbs, about 60% the length of the hindlimb in Guanlong, with the typical three digits of coelurosaurs. [3] The long forelimb persisted at least through the Early Cretaceous Eotyrannus, [5] but is unknown in Appalachiosaurus. [8] Derived tyrannosaurids have forelimbs strongly reduced in size, the most extreme example being Tarbosaurus from Mongolia, where the humerus was only one-quarter the length of the femur. [1] The third digit of the forelimb was also reduced over time. This digit was unreduced in the basal Guanlong, [3] while in Dilong it was more slender than the other two digits. [2] Eotyrannus also had three functional digits on each hand. [5] Tyrannosaurids had only two, although the vestigial metacarpal of the third are preserved in some well-preserved specimens. [9] As in most coelurosaurs, the second digit of the hand is the largest, even when the third digit is not present.

Characteristic features of the tyrannosauroid pelvis include a concave notch at the upper front end of the ilium, a sharply defined vertical ridge on the outside surface of the ilium, extending upwards from the acetabulum (hip socket), and a huge "boot" on the end of the pubis, more than half as long as the shaft of the pubis itself. [1] These features are found in all known tyrannosauroids, including basal members Guanlong [3] and Dilong. [2] The pubis is not known in Aviatyrannis or Stokesosaurus but both show typical tyrannosauroid characters in the ilium. [10] The hindlimbs of all tyrannosauroids, like most theropods, had four toes, although the first toe (the hallux) did not contact the ground. Tyrannosauroid hindlimbs are longer relative to body size than almost any other theropods, and show proportions characteristic of fast-running animals, including elongated tibiae and metatarsals. [1] These proportions persist even in the largest adult Tyrannosaurus, [11] despite its probable inability to run. [12] The third metatarsal of tyrannosaurids was pinched at the top between the second and fourth, forming a structure known as the arctometatarsus. [1] The arctometatarsus was also present in Appalachiosaurus [8] but it is unclear whether it was found in Eotyrannus [5] or Dryptosaurus . [13] This structure was shared by derived ornithomimids, troodontids and caenagnathids, [14] but was not present in basal tyrannosauroids like Dilong paradoxus , indicating convergent evolution. [2]

Classification

Skull of Proceratosaurus, a proceratosaurid tyrannosauroid from the Middle Jurassic of England. Proceratosaurus holotype skull.jpg
Skull of Proceratosaurus , a proceratosaurid tyrannosauroid from the Middle Jurassic of England.

Tyrannosaurus was named by Henry Fairfield Osborn in 1905, along with the family Tyrannosauridae. [15] The name is derived from the Ancient Greek words τυραννοςtyrannos ('tyrant') and σαυροςsauros ('lizard'). The superfamily name Tyrannosauroidea was first published in a 1964 paper by the British paleontologist Alick Walker. [16] The suffix -oidea, commonly used in the name of animal superfamilies, is derived from the Greek ειδοςeidos ('form'). [17]

Scientists have commonly understood Tyrannosauroidea to include the tyrannosaurids and their immediate ancestors. [16] [18] With the advent of phylogenetic taxonomy in vertebrate paleontology, however, the clade has received several more explicit definitions. The first was by Paul Sereno in 1998, where Tyrannosauroidea was defined as a stem-based taxon including all species sharing a more recent common ancestor with Tyrannosaurus rex than with neornithean birds. [19] To make the family more exclusive, Thomas Holtz redefined it in 2004 to include all species more closely related to Tyrannosaurus rex than to Ornithomimus velox , Deinonychus antirrhopus or Allosaurus fragilis . [1] Sereno published a new definition in 2005, using Ornithomimus edmontonicus, Velociraptor mongoliensis and Troodon formosus as external specifiers. [20] The Sereno definition was adopted in a 2010 review. [6]

Some studies have suggested that the clade Megaraptora, usually considered to be allosauroids, are basal tyrannosauroids. [21] [22] However, other authors disputed the placement of megaraptorans within Tyrannosauroidea, [23] [24] and a study of megaraptoran hand anatomy published in 2016 caused even the original scientists suggesting their tyrannosauroid relationships to at least partly reject their prior conclusion. [25]

Phylogeny

While paleontologists have long recognized the family Tyrannosauridae, its ancestry has been the subject of much debate. For most of the twentieth century, tyrannosaurids were commonly accepted as members of the Carnosauria, which included almost all large theropods. [26] [27] Within this group, the allosaurids were often considered to be ancestral to tyrannosaurids. [18] [28] In the early 1990s, cladistic analyses instead began to place tyrannosaurids into the Coelurosauria, [14] [29] echoing suggestions first published in the 1920s. [30] [31] Tyrannosaurids are now universally considered to be large coelurosaurs. [1] [3] [32] [33] [34] [35] [36]

In 1994, Holtz grouped tyrannosauroids with elmisaurids, ornithomimosaurs and troodonts into a coelurosaurian clade called Arctometatarsalia based on a common ankle structure where the second and fourth metatarsals meet near the tarsal bones, covering the third metatarsal when viewed from the front. [14] Basal tyrannosauroids like Dilong, however, were found with non-arctometatarsalian ankles, indicating that this feature evolved convergently. [2] Arctometatarsalia has been dismantled and is no longer used by most paleontologists, with tyrannosauroids usually considered to be basal coelurosaurs outside Maniraptoriformes. [1] [34] [36] While many place tyrannosauroids as basal coelurosaurs, Paul Sereno in his 1990s analysis of theropods would find the Tyrannosaurs to be sister taxa to the Maniraptora with them being closer to birds than Ornithomimosaurs were. He called this group Tyrannoraptora (which in the absence of papers that recover a Tyrannosaur-maniraptoran clade), is a clade which contains most Coelurosaurs. [37] A 2007 analysis found the family Coeluridae, including the Late Jurassic North American genera Coelurus and Tanycolagreus , to be the sister group of Tyrannosauroidea. [32]

The most basal tyrannosauroid known from complete skeletal remains is Guanlong, a representative of the family Proceratosauridae. [3] [38] Other early taxa include Stokesosaurus and Aviatyrannis, known from far less complete material. [10] The better-known Dilong is considered slightly more derived than Guanlong and Stokesosaurus. [2] [3] Dryptosaurus , long a difficult genus to classify, has turned up in several recent analyses as a basal tyrannosauroid as well, slightly more distantly related to Tyrannosauridae than Eotyrannus and Appalachiosaurus. [1] [8] [39] Alectrosaurus , a poorly known genus from Mongolia, is definitely a tyrannosauroid but its exact relationships are unclear. [1] Other taxa have been considered possible tyrannosauroids by various authors, including Bagaraatan and Labocania . [1] Siamotyrannus from the Early Cretaceous of Thailand was originally described as an early tyrannosaurid, [40] but is usually considered a carnosaur today. [34] [41] Iliosuchus has a vertical ridge on the ilium reminiscent of tyrannosauroids and may in fact be the earliest known member of the superfamily, but not enough material is known to be sure. [10] [41]

Below on the left is a cladogram of Tyrannosauroidea from a 2022 study by Darren Naish and Andrea Cau on the genus Eotyrannus , and on the right is a cladogram of Eutyrannosauria from a 2020 study by Jared T. Voris and colleagues on the genus Thanatotheristes : [42] [43]

Tyrannosauroidea

Phylogeography

In 2018 authors Rafael Delcourt and Orlando Nelson Grillo published a phylogenetic analysis of Tyrannosauroidea which incorporated taxa from the ancient continent of Gondwana (which today consists of the southern hemisphere), such as Santanaraptor and Timimus , whose placement in the group has been controversial. [44] They have found that not only Santanaraptor and Timimus were placed as tyrannosaurs more derived than Dilong, but they have found in their analysis that tyrannosauroids were widespread in Laurasia and Gondwana since the Middle Jurassic. [44] They have proposed new subclade names for Tyrannosaurioidea. The first is Pantyrannosauria referring to all non-proceratosaurid members of the group, while Eutyrannosauria for larger tyrannosaur taxa found in the northern hemisphere such as Dryptosaurus, Appalachiosaurus, Bistahieversor , and Tyrannosauridae. [44] Below is their phylogeographic tree they have recovered, in which displays the phylogenetic relationships of the taxa as well as the continents those taxa have been found. [44]

In 2021, Chase Brownstein published a research article based on more thorough descriptions of tyrannosauroid metatarsals and vertebra from the Merchantville Formation in Delaware. [45] This reanalysis of phylogenetic relationships of tyrannosauroids in Appalachia has brought the rediscovery of the clade Dryptosauridae due to the similarities of metatarsals II and IV with the same bones in the Dryptosaurus holotype. [45] However. the Merchantville taxon was found to still be different enough to separate it on the genus level from Dryptosaurus. In the phylogentic tree constructed Dryptosauridae is found to be a valid family of non tyrannosaurid eutyrannosaur. It currently sits in a polytomy with the Iren Dabasu taxon and more basal eutryannosaurs. [45]

Distribution

The tyrannosauroids lived on the supercontinent Laurasia, which split from Gondwana in the Middle Jurassic. The earliest recognized tyrannosauroids lived in the Middle Jurassic, represented by the proceratosaurids Kileskus from the Western Siberia and Proceratosaurus from Great Britain. Upper Jurassic tyrannosauroids include Guanlong from China, Stokesosaurus from the western United States and Aviatyrannis and Juratyrant from Europe.

Confirmed tyrannosauroid fossils have only been discovered in the northern continents, with possible basal tyrannosauroid fossils reported from Australia. Late Cretaceous tyrannosauroids are known only from North America and Asia. Tyrannosauroid fossil localities map.png
Confirmed tyrannosauroid fossils have only been discovered in the northern continents, with possible basal tyrannosauroid fossils reported from Australia. Late Cretaceous tyrannosauroids are known only from North America and Asia.

Early Cretaceous tyrannosauroids are known from Laurasia, being represented by Eotyrannus from England [5] and Dilong , Sinotyrannus , and Yutyrannus from northeastern China. Early Cretaceous tyrannosauroid premaxillary teeth are known from the Cedar Mountain Formation in Utah [46] and the Tetori Group of Japan. [47]

The Middle Cretaceous record of Tyrannosauroidea is rather patchy. Teeth and indeterminate postcrania of this interval are known from the Cenomanian-age Dakota Formation of western North America and Potomac Formation of New Jersey, [46] [48] as well as formations in Kazakhstan and Tajikistan; [49] two genera, Timurlengia and Xiongguanlong, have been found in Asia, while the Brazilian Santanaraptor may belong to this group. [24] Suskityrannus has been found in the Moreno Hill Formation of the Zuni Basin of western New Mexico. [50] [51] The first unquestionable remains of tyrannosaurids occur in the Campanian stage of the Late Cretaceous in North America and Asia. Two subfamilies are recognized. The albertosaurines are only known from North America, while the tyrannosaurines are found on both continents. [1] Tyrannosaurid fossils have been found in Alaska, which may have served as a land bridge allowing dispersal between the two continents. [52] Non-tyrannosaurid tyrannosauroids like Alectrosaurus and possibly Bagaraatan were contemporaneous with tyrannosaurids in Asia, while they are absent from western North America. [1] Eastern North America was divided by the Western Interior Seaway in the middle of the Cretaceous and isolated from the western portion of the continent. The absence of tyrannosaurids from the eastern part of the continent suggests that the family evolved after the appearance of the seaway, allowing basal tyrannosauroids like Dryptosaurus and Appalachiosaurus to survive in the east as a relict population until the end of the Cretaceous. [8]

Basal tyrannosauroids have also been suggested to be present in Australia and South America during the Early Cretaceous. NMV P186069, a partial pubis (a hip bone) with a supposed distinctive tyrannosauroid-like form, was discovered in Dinosaur Cove in Victoria. [53] However, a response suggested that critical tyrannosauroid characters were absent from the fossil. [54] The Australian taxon Timimus , known from a femur, and the Brazilian Santanaraptor , known from a partial juvenile skeleton, have also been suggested to be tyrannosaurs. [44] However, these placements have been considered questionable, with the supposed tyrannosauroid characters of Santanaraptor being widely distributed within Coelurosauria, in other characters having similarities to noasaurids. [55]

Paleobiology

Facial tissue

A conference paper by Tracy Ford states that there was rough bone texture on the skulls of theropods and higher foramina frequency than lepidosaurs and mammals which would be evidential for a sensitive snout for theropods. [56] [57] A study in 2017 study on a new tyrannosaurid named Daspletosaurus horneri was published in the journal Scientific Reports, where paleontologist Thomas Carr analyzed the craniofacial texture of Daspletosaurus horneri and observed a hummocky rugosity which compared to crocodilian skulls, suggesting Daspletosaurus horneri and with it all tyrannosaurids have flat sensory scales. The subordinate regions were analyzed to have cornified epidermis. [58] However, a 2018 presentation has an alternative interpretation. Crocodilians do not have flat sensory scales, but rather cracked, cornified epidermis due to growth. The hummocky rugosity in the skulls of lepidosaurs have correlation with scales which this bone texture is also present in tyrannosaurid skulls. The foramina frequency in theropod skulls does not exceed 50 foramina, which shows that theropods had lips. It's been proposed that lips are a primitive trait in tetrapods and the soft tissue present in crocodilians are a derived trait because of aquatic or semiaquatic adaptations. [59] [60] [61] [62] [63]

Body integument

Long filamentous structures have been preserved along with skeletal remains of numerous coelurosaurs from the Early Cretaceous Yixian Formation and other nearby geological formations from Liaoning, China. [64] These filaments have usually been interpreted as "protofeathers," homologous with the branched feathers found in birds and some non-avian theropods, [65] [66] although other hypotheses have been proposed. [67] A skeleton of Dilong paradoxus was described in 2004 that included the first example of feathers in a tyrannosauroid. Similarly to down feathers of modern birds, the feathers found in Dilong were branched but not pennaceous, and may have been used for insulation. [2] Even large tyrannosauroids have been found with evidence of feathers. Yutyrannus huali , also from the Yixian Formation, is known from three specimens, each preserving traces of feathers on various parts of the body. While not all areas of the body preserve impressions across all three specimens, these fossils demonstrate that even in this medium-sized species, most of the body was covered in feathers. [68]

The presence of feathers in basal tyrannosauroids is not surprising since they are now known to be characteristic of coelurosaurs, found in other basal genera like Sinosauropteryx , [65] as well as all more derived groups. [64] Rare fossilized skin impressions of some Late Cretaceous tyrannosaurids lack feathers, however, instead showing skin covered in fine, non-overlapping scales. [69] Possibly, feathers were present on other areas of the body: preserved skin impressions are very small and come primarily from the legs, pelvic region, and underside of the tail, which either lack feathers or only covered in a light down in some modern large ground-dwelling birds. Alternatively, secondary loss of feathers in large tyrannosaurids may be analogous with the similar loss of hair in the largest modern mammals like elephants, where a low surface area-to-volume ratio slows down heat transfer, making insulation by a coat of hair unnecessary or even detrimental. [2] A scientific publication by Phil Bell and colleagues in 2017 show that tyrannosaurids such as Gorgosaurus, Tarbosaurus, Albertosaurus, Daspletosaurus, and Tyrannosaurus had scales. The Bell et al. 2017 paper notes that the scale-like integument on bird feet were actually secondarily derived feathers according to paleontological and evolutionary developmental evidence so they hypothesize that the scaly skin preserved on some tyrannosaurid specimens might be secondarily derived from filamentous appendages like on Yutyrannus although strong evidence is needed to support this hypothesis. [70] [71] [72] However, other paleontologists argue that taphonomy is the possible cause of the lack of filamentous structures in tyrannosaurid fossils. [73]

Head crests

The elaborate head crest of Guanlong, a basal tyrannosauroid from China. Guanlong wucaii head.jpg
The elaborate head crest of Guanlong , a basal tyrannosauroid from China.

Bony crests are found on the skulls of many theropods, including numerous tyrannosauroids. The most elaborate is found in Guanlong, where the nasal bones support a single, large crest which runs along the midline of the skull from front to back. This crest was penetrated by several large foramina (openings) which reduced its weight. [3] A less prominent crest is found in Dilong, where low, parallel ridges run along each side of the skull, supported by the nasal and lacrimal bones. These ridges curve inwards and meet just behind the nostrils, making the crest Y-shaped. [2] The fused nasals of tyrannosaurids are often very rough-textured. Alioramus , a possible tyrannosaurid from Mongolia, bears a single row of five prominent bony bumps on the nasal bones; a similar row of much lower bumps is present on the skull of Appalachiosaurus, as well as some specimens of Daspletosaurus , Albertosaurus, and Tarbosaurus. [8] In Albertosaurus, Gorgosaurus and Daspletosaurus , there is a prominent horn in front of each eye on the lacrimal bone. The lacrimal horn is absent in Tarbosaurus and Tyrannosaurus, which instead have a crescent-shaped crest behind each eye on the postorbital bone. [1]

These head crests may have been used for display, perhaps for species recognition or courtship behavior. [1] An example of the handicap principle may be the case of Guanlong, where the large, delicate crest may have been a hindrance to hunting in what was presumably an active predator. If an individual was healthy and successful at hunting despite the fragile crest, it would indicate the superior quality of the individual over others with smaller crests. Similarly to the unwieldy tail of a male peacock or the outsized antlers of an Irish elk, the crest of Guanlong may have evolved via sexual selection, providing an advantage in courtship that outweighed any decrease in hunting ability. [3]

Reproduction

Neonate sized tyrannosaur fossils have been documented in the scientific literature. [74]

Related Research Articles

<span class="mw-page-title-main">Tyrannosauridae</span> Family of dinosaurs

Tyrannosauridae is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to fifteen genera, including the eponymous Tyrannosaurus. The exact number of genera is controversial, with some experts recognizing as few as three. All of these animals lived near the end of the Cretaceous Period and their fossils have been found only in North America and Asia.

<i>Dilong paradoxus</i> Extinct species of dinosaur

Dilong is a genus of small basal tyrannosauroid dinosaurs. The only species in the genus is Dilong paradoxus, known from the Lower Cretaceous Yixian Formation of East Asia. The discovery of Dilong was significant as it provided the first evidence of feathers in tyrannosaurs, something which had previously been suspected for the group.

<span class="mw-page-title-main">Coelurosauria</span> Clade of dinosaurs

Coelurosauria is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs.

<i>Appalachiosaurus</i> Extinct genus of dinosaurs

Appalachiosaurus is a genus of tyrannosaurian theropod dinosaur from the Late Cretaceous period of what is now eastern North America. It was a basal member of the Eutyrannosauria clade meaning it was rather close in relation to the true tyrannosaurids such as Tyrannosaurus. Like most theropods, it was a bipedal predator. Only a juvenile skeleton has been found, representing an animal approximately 6.5 metres (21 ft) long and weighing 623 kilograms (1,373 lb), which indicates an adult would have been significantly larger.

<i>Proceratosaurus</i> Extinct genus of dinosaurs

Proceratosaurus is a genus of carnivorous theropod dinosaur from the Middle Jurassic (Bathonian) of England. It contains a single species. P. bradleyi, known from a mostly complete skull and lower jaws. Proceratosaurus was a small dinosaur, estimated to measure around 3 m (9.8 ft) in length. Its name refers to how it was originally thought to be an ancestor of Ceratosaurus, due to the partially preserved portion of the crest of Proceratosaurus superficially resembling the small crest of Ceratosaurus. Now, however, it is considered a coelurosaur, specifically a member of the family Proceratosauridae, and amongst the earliest known members of the clade Tyrannosauroidea.

<i>Alioramus</i> Tyrannosaurid theropod dinosaur genus from the Late Cretaceous period

Alioramus is a genus of tyrannosaurid theropod dinosaurs from the Late Cretaceous period of Asia. It currently contains two species. The type species, A. remotus is known from a partial skull and three foot bones recovered from the Mongolian Nemegt Formation, which was deposited in a humid floodplain about 70 million years ago. These remains were named and described by Soviet paleontologist Sergei Kurzanov in 1976. A second species, A. altai, known from a much more complete skeleton also from the Nemegt Formation, was named and described by Stephen L. Brusatte and colleagues in 2009. Its relationships to other tyrannosaurid genera were at first unclear, with some evidence supporting a hypothesis that Alioramus was closely related to the contemporary species Tarbosaurus bataar. However, the discovery of Qianzhousaurus indicates that it belongs to a distinct branch of tyrannosaurs, namely the tribe Alioramini.

<i>Dryptosaurus</i> Extinct genus of dinosaurs

Dryptosaurus is a genus of basal eutyrannosaurian theropod dinosaur that lived on the island continent of Appalachia approximately 67.6 million years ago during the end of the Maastrichtian age of the Late Cretaceous period. Dryptosaurus was a large, bipedal, ground-dwelling carnivore that could grow up to 7.5 metres (25 ft) long and weigh up to 756–1,500 kilograms (1,667–3,307 lb). Although it is now largely unknown outside of academic circles, the famous 1897 painting of the genus by Charles R. Knight made Dryptosaurus one of the more widely known dinosaurs of its time, in spite of its poor fossil record. First described by Edward Drinker Cope in 1866 and later renamed by Othniel Charles Marsh in 1877, Dryptosaurus is among the first theropod dinosaurs ever known to science.

<i>Guanlong</i> Extinct genus of reptiles

Guanlong (冠龍) is a genus of extinct proceratosaurid tyrannosauroid dinosaur from the Late Jurassic of China. The taxon was first described in 2006 by Xu Xing et al., who found it to represent a new taxon related to Tyrannosaurus. The name is derived from Chinese, translating as "crown dragon". Two individuals are currently known, a partially complete adult and a nearly complete juvenile. These specimens come from the Oxfordian stage of the Chinese Shishugou Formation.

<i>Santanaraptor</i> Extinct genus of dinosaurs

Santanaraptor is a genus of tyrannosauroid theropod dinosaur that lived in South America during the Early Cretaceous, about 112 million years ago.

<span class="mw-page-title-main">Tyrannosaurinae</span> Extinct subfamily of dinosaurs

Tyrannosaurinae is one of the two extinct subfamilies of Tyrannosauridae, a family of coelurosaurian theropods that consists of at least three tribes and several genera. All fossils of these genera have been found in the Late Cretaceous deposits of western North America and east Asia. Compared to the related subfamily Albertosaurinae, tyrannosaurines overall are more robust and larger though the alioramins were gracile by comparison. This subfamily also includes the oldest known tyrannosaurid genus Lythronax as well as the youngest and most famous member of the group, Tyrannosaurus rex. There were at least 30 different species of tyrannosaurines.

<i>Xiongguanlong</i> Extinct genus of dinosaurs

Xiongguanlong is an extinct genus of tyrannosauroid theropod from the Early Cretaceous period of what is now China. The type and only species is X. baimoensis. The generic name comes from Jiayuguan City and the Mandarin word "long" which means dragon. The specific epithet, "baimoensis" is a latinization of the Mandarin word for "white ghost" in reference to one of the geological features of the type locality.

<i>Sinotyrannus</i> Extinct genus of dinosaurs

Sinotyrannus was an early, large-bodied genus within the superfamily Tyrannosauroidea. This dinosaur had a single type species, S. kazuoensis, with the only known specimen containing a partial skull, some vertebrae, and a hip, all of which were found in the Early Cretaceous aged Jiufotang Formation of Liaoning, China. While it exhibited greater body size that would put it on par with the later tyrannosaurids such as Tyrannosaurus, Sinotyrannus was probably a member of the basal tyrannosaur family known as the Proceratosauridae. This family originated in the Jurassic, whose members are known from Europe and Asia. Sinotyrannus, alongside another early tyrannosaur, Yutyrannus, appears to have been oddly large when compared to most tyrannosaurs of the Early Cretaceous, such as Dilong. Most of the world during the Early Cretaceous was dominated by more basal tetanurans, such as the megalosaurs and allosaurs, with tyrannosaurids themselves only taking over after both groups started to decline. However, Sinotyrannus and Yutyrannus appear to be exceptions to this. Sinotyrannus was the largest theropod in the Jiufotang Formation, reaching up to 10 meters in overall length and having a general mass similar to that of a large rhino.

<span class="mw-page-title-main">Megaraptora</span> Extinct clade of dinosaurs

Megaraptora is a clade of carnivorous theropod dinosaurs with controversial relationships to other tetanuran theropods. Its derived members, the Megaraptoridae are noted for their large hand claws and powerfully-built forelimbs, which are usually reduced in size in other large theropods.

<span class="mw-page-title-main">Proceratosauridae</span> Extinct family of dinosaurs

Proceratosauridae is a family or clade of tyrannosauroid theropod dinosaurs from the Middle Jurassic to the Early Cretaceous.

<i>Bistahieversor</i> Extinct genus of dinosaurs

Bistahieversor, also known as the "Bisti Beast", is a genus of basal eutyrannosaurian theropod dinosaur. The genus contains only a single known species, B. sealeyi, described in 2010, from the Late Cretaceous of New Mexico. The holotype and a juvenile were found in the Hunter Wash Member of the Kirtland Formation, while other specimens came from the underlying Fossil Forest member of the Fruitland Formation. This dates Bistahieversor approximately 75.5 to 74.5 million years ago during the Campanian age, found in sediments spanning a million years.

<i>Yutyrannus</i> Genus of proceratosaurid dinosaur from the Early Cretaceous period

Yutyrannus is a genus of proceratosaurid tyrannosauroid dinosaur which contains a single known species, Yutyrannus huali. This species lived during the early Cretaceous period in what is now northeastern China. Three fossils of Yutyrannus huali —all found in the rock beds of Liaoning Province— are currently the largest-known dinosaur specimens that preserve direct evidence of feathers.

<i>Lythronax</i> Genus of tyrannosaurid dinosaur from the Late Cretaceous period

Lythronax is a genus of tyrannosaurid dinosaur that lived in North America around 81.9-81.5 million years ago during the Late Cretaceous period. The only known specimen was discovered in Utah in the Wahweap Formation of the Grand Staircase–Escalante National Monument in 2009, and it consists of a partial skull and skeleton. In 2013, it became the basis of the new genus and species Lythronax argestes; the generic name Lythronax means "gore king", and the specific name argestes originates from the Greek poet Homer's name for the wind from the southwest, in reference to the specimen's geographic provenance in North America.

<span class="mw-page-title-main">Alioramini</span> Extinct tribe of tyrannosaurid dinosaurs

Alioramini is a tribe of long-snouted tyrannosaurine tyrannosaurids from the Late Cretaceous epoch. It includes the tyrannosaurid genera Alioramus and Qianzhousaurus. Although tyrannosaurids are known from a variety of places around the globe, alioramins are currently restricted to Asia in mostly Maastrichtian strata. Many of the fossils attributed to Alioramini are not from fully developed individuals.

<span class="mw-page-title-main">Timeline of tyrannosaur research</span>

This timeline of tyrannosaur research is a chronological listing of events in the history of paleontology focused on the tyrannosaurs, a group of predatory theropod dinosaurs that began as small, long-armed bird-like creatures with elaborate cranial ornamentation but achieved apex predator status during the Late Cretaceous as their arms shrank and body size expanded. Although formally trained scientists did not begin to study tyrannosaur fossils until the mid-19th century, these remains may have been discovered by Native Americans and interpreted through a mythological lens. The Montana Crow tradition about thunder birds with two claws on their feet may have been inspired by isolated tyrannosaurid forelimbs found locally. Other legends possibly inspired by tyrannosaur remains include Cheyenne stories about a mythical creature called the Ahke, and Delaware stories about smoking the bones of ancient monsters to have wishes granted.

<i>Timurlengia</i> Extinct genus of dinosaurs

Timurlengia is an extinct genus of tyrannosauroid theropod dinosaur found in Uzbekistan, in the Bissekty Formation in the Kyzylkum Desert, hailing from the Turonian age of the early Late Cretaceous. The type species is Timurlengia euotica.

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