Tyrannosaurids
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Tyrannosauridae (or tyrannosaurids, meaning "
tyrant A tyrant (), in the modern English usage of the word, is an absolute ruler who is unrestrained by law, or one who has usurped a legitimate ruler's sovereignty. Often portrayed as cruel, tyrants may defend their positions by resorting to ...
lizards") is a
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
of
coelurosauria Coelurosauria (; from Greek, meaning "hollow-tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, tyra ...
n
theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
s that comprises two subfamilies containing up to fifteen
genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...
, including the
eponym An eponym is a noun after which or for which someone or something is, or is believed to be, named. Adjectives derived from the word ''eponym'' include ''eponymous'' and ''eponymic''. Eponyms are commonly used for time periods, places, innovati ...
ous ''
Tyrannosaurus ''Tyrannosaurus'' () is a genus of large theropod dinosaur. The type species ''Tyrannosaurus rex'' ( meaning 'king' in Latin), often shortened to ''T. rex'' or colloquially t-rex, is one of the best represented theropods. It lived througho ...
''. 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 The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
Period and their
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
s have been found only in
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
and
Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...
. Although descended from smaller ancestors, tyrannosaurids were almost always the largest
predators Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...
in their respective
ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...
s, putting them at the
apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics) A-Bomb Abomination Absorbing Man Abraxas Abyss Abyss is the name of two characters appearing in Ameri ...
of the
food chain A food chain is a linear network of links in a food web, often starting with an autotroph (such as grass or algae), also called a producer, and typically ending at an apex predator (such as grizzly bears or killer whales), detritivore (such as ...
. The largest
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
was ''Tyrannosaurus rex'', the most massive known terrestrial predator, which measured over in length and according to most modern estimates up to in weight. Tyrannosaurids were
bipedal Bipedalism is a form of terrestrial locomotion where an animal moves by means of its two rear (or lower) limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' ...
carnivores with massive
skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...
s filled with large teeth. Despite their large size, their legs were long and proportioned for fast movement. In contrast, their arms were very small, bearing only two functional digits. Unlike most other groups of dinosaurs, very complete remains have been discovered for most known tyrannosaurids. This has allowed a variety of research into their
biology Biology is the scientific study of life and living organisms. It is a broad natural science that encompasses a wide range of fields and unifying principles that explain the structure, function, growth, History of life, origin, evolution, and ...
. Scientific studies have focused on their
ontogeny Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the ovum, egg to adult. The term can also be used to refer to t ...
,
biomechanics Biomechanics is the study of the structure, function and motion of the mechanical aspects of biological systems, at any level from whole organisms to Organ (anatomy), organs, Cell (biology), cells and cell organelles, using the methods of mechani ...
and
ecology Ecology () is the natural science of the relationships among living organisms and their Natural environment, environment. Ecology considers organisms at the individual, population, community (ecology), community, ecosystem, and biosphere lev ...
, among other subjects.


History of discovery

The first remains of tyrannosaurids were uncovered during expeditions led by the
Geological Survey of Canada The Geological Survey of Canada (GSC; , CGC) is a Canadian federal government agency responsible for performing geological surveys of the country developing Canada's natural resources and protecting the environment. A branch of the Earth Science ...
, which located numerous scattered teeth. These distinctive dinosaur teeth were given the name '' Deinodon'' ("terrible tooth") by
Joseph Leidy Joseph Mellick Leidy (September 9, 1823 – April 30, 1891) was an American paleontologist, parasitologist and anatomist. Leidy was professor of anatomy at the University of Pennsylvania, later becoming a professor of natural history at Swarth ...
in 1856. The first good specimens of a tyrannosaurid were found in the Horseshoe Canyon Formation of
Alberta Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...
, and consisted of nearly complete skulls with partial skeletons. These remains were first studied by
Edward Drinker Cope Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontology, paleontologist, comparative anatomy, comparative anatomist, herpetology, herpetologist, and ichthyology, ichthyologist. Born to a wealthy Quaker fam ...
in 1876, who considered them a species of the eastern tyrannosauroid '' Dryptosaurus''. In 1905,
Henry Fairfield Osborn Henry Fairfield Osborn, Sr. (August 8, 1857 – November 6, 1935) was an American paleontologist, geologist and eugenics advocate. He was professor of anatomy at Columbia University, president of the American Museum of Natural History for 25 y ...
recognized that the Alberta remains differed considerably from ''Dryptosaurus'', and coined a new name for them: ''
Albertosaurus sarcophagus ''Albertosaurus'' (; meaning "Alberta lizard") is a genus of large tyrannosaurid theropod dinosaur that lived in northwestern North America during the early to middle Maastrichtian age of the Late Cretaceous period, about 71 million yea ...
'' ("flesh-eating Alberta lizard"). Cope described more tyrannosaur material in 1892, in the form of isolated vertebrae, and gave this animal the name '' Manospondylus gigas''. This discovery was mostly overlooked for over a century, and caused controversy in the early 2000s when it was discovered that this material actually belonged to, and had name priority over, ''
Tyrannosaurus rex ''Tyrannosaurus'' () is a genus of large theropoda, theropod dinosaur. The type species ''Tyrannosaurus rex'' ( meaning 'king' in Latin), often shortened to ''T. rex'' or colloquially t-rex, is one of the best represented theropods. It live ...
''. In his 1905 paper naming ''Albertosaurus'', Osborn described two additional tyrannosaur specimens that had been collected in
Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...
and
Wyoming Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...
during a 1902 expedition of the
American Museum of Natural History The American Museum of Natural History (AMNH) is a natural history museum on the Upper West Side of Manhattan in New York City. Located in Theodore Roosevelt Park, across the street from Central Park, the museum complex comprises 21 interconn ...
, led by
Barnum Brown Barnum Brown (February 12, 1873 – February 5, 1963), commonly referred to as Mr. Bones, was an American paleontologist. He discovered the first documented remains of ''Tyrannosaurus'' during a career that made him one of the most famous fossil ...
. Initially, Osborn considered these to be distinct species. The first, he named ''Dynamosaurus imperiosus'' ("emperor power lizard"), and the second, ''Tyrannosaurus rex'' ("king tyrant lizard"). A year later, Osborn recognized that these two specimens actually came from the same species. Despite the fact that ''Dynamosaurus'' had been found first, the name ''Tyrannosaurus'' had appeared one page earlier in his original article describing both specimens. Therefore, according to the
International Code of Zoological Nomenclature The International Code of Zoological Nomenclature (ICZN) is a widely accepted Convention (norm), convention in zoology that rules the formal scientific name, scientific naming of organisms treated as animals. It is also informally known as the I ...
(ICZN), the name ''Tyrannosaurus'' was used. Barnum Brown went on to collect several more tyrannosaurid specimens from Alberta, including the first to preserve the shortened, two-fingered forelimbs characteristic of the group (which Lawrence Lambe named ''
Gorgosaurus libratus ''Gorgosaurus'' ( ; ) is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period (geology), Period (Campanian), between about 76.5 and 75 million years ago. Fossil remains have been ...
'', "balanced fierce lizard", in 1914). A second significant find attributed to ''Gorgosaurus'' was made in 1942, in the form of a well-preserved, though unusually small, complete skull. The specimen waited until after the end of
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
to be studied by Charles W. Gilmore, who named it ''Gorgosaurus lancesnis''. This skull was re-studied by Robert T. Bakker, Phil Currie, and Michael Williams in 1988, and assigned to the new genus '' Nanotyrannus''. It was also in 1946 that paleontologists from the
Soviet Union The Union of Soviet Socialist Republics. (USSR), commonly known as the Soviet Union, was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 until Dissolution of the Soviet ...
began expeditions into
Mongolia Mongolia is a landlocked country in East Asia, bordered by Russia to the north and China to the south and southeast. It covers an area of , with a population of 3.5 million, making it the world's List of countries and dependencies by po ...
, and uncovered the first tyrannosaur remains from Asia. Evgeny Maleev described new Mongolian species of ''Tyrannosaurus'' and ''Gorgosaurus'' in 1955, and one new genus: '' Tarbosaurus'' ("terrifying lizard"). Subsequent studies, however, showed that all of Maleev's tyrannosaur species were actually one species of ''Tarbosaurus'' at different stages of growth. A second species of Mongolian tyrannosaurid was found later, described by Sergei Kurzanov in 1976, and given the name ''
Alioramus remotus ''Alioramus'' (; meaning 'different branch') 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 meta ...
'' ("remote different branch"), though its status as a true tyrannosaurid and not a more primitive tyrannosaur is still controversial.


Description

The tyrannosaurids were all large animals, with all species capable of weighing at least 1 metric ton. A single specimen of '' Alioramus'' of an individual estimated at between long has been discovered, although it is considered by some experts to be a juvenile. ''
Albertosaurus ''Albertosaurus'' (; meaning "Alberta lizard") is a genus of large tyrannosaurid theropod dinosaur that lived in northwestern North America during the early to middle Maastrichtian age of the Late Cretaceous period, about 71 million yea ...
'', ''
Gorgosaurus ''Gorgosaurus'' ( ; ) is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period (Campanian), between about 76.5 and 75 million years ago. Fossil remains have been found in the Ca ...
'' and '' Daspletosaurus'' all measured between long, while '' Tarbosaurus'' reached lengths of from snout to tail. The massive ''
Tyrannosaurus ''Tyrannosaurus'' () is a genus of large theropod dinosaur. The type species ''Tyrannosaurus rex'' ( meaning 'king' in Latin), often shortened to ''T. rex'' or colloquially t-rex, is one of the best represented theropods. It lived througho ...
'' reached in the largest specimen, RSM P2523.8.


Skull and dentition

Tyrannosaurid skull anatomy is well understood, as complete skulls are known for all genera but ''Alioramus'', which is known only from partial skull remains. ''Tyrannosaurus'', ''Tarbosaurus'', and ''Daspletosaurus'' had skulls that exceeded in length. Adult tyrannosaurids had tall, massive skulls, with many bones fused and reinforced for strength. At the same time, hollow chambers within many skull bones and large openings (
fenestra A fenestra (fenestration; : fenestrae or fenestrations) is any small opening or pore, commonly used as a term in the biology, biological sciences. It is the Latin word for "window", and is used in various fields to describe a pore in an anatomy, ...
e) between those bones helped to reduce skull weight. Many features of tyrannosaurid skulls were also found in their immediate ancestors, including tall
premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...
e and fused
nasal bone The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face and by their junction, form the bridge of the upper one third of the nose. Eac ...
s. Tyrannosaurid skulls had many unique characteristics, including fused
parietal bone The parietal bones ( ) are two bones in the skull which, when joined at a fibrous joint known as a cranial suture, form the sides and roof of the neurocranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four bord ...
s with a prominent
sagittal crest A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are excepti ...
, which ran longitudinally along the
sagittal suture The sagittal suture, also known as the interparietal suture and the ''sutura interparietalis'', is a dense, fibrous connective tissue joint between the two parietal bones of the skull. The term is derived from the Latin word ''sagitta'', meaning ...
and separated the two supratemporal fenestrae on the skull roof. Behind these fenestrae, tyrannosaurids had a characteristically tall nuchal crest, which also arose from the parietals but ran along a
transverse plane A transverse plane is a plane that is rotated 90° from two other planes. Anatomy The transverse plane is an anatomical plane that is perpendicular to the sagittal plane and the dorsal plane. It is also called the axial plane or horizonta ...
rather than longitudinally. The nuchal crest was especially well-developed in ''Tyrannosaurus'', ''Tarbosaurus'' and ''Alioramus''. ''Albertosaurus'', ''Daspletosaurus'' and ''Gorgosaurus'' had tall crests in front of the eyes on the
lacrimal bone The lacrimal bones are two small and fragile bones of the facial skeleton; they are roughly the size of the little fingernail and situated at the front part of the medial wall of the orbit. They each have two surfaces and four borders. Several bon ...
s, while ''Tarbosaurus'' and ''Tyrannosaurus'' had extremely thickened
postorbital The ''postorbital'' is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some ve ...
bones forming crescent-shaped crests behind the eyes. ''Alioramus'' had a row of six bony crests on top of its snout, arising from the nasal bones; lower crests have been reported on some specimens of ''Daspletosaurus'' and ''Tarbosaurus'', as well as the more basal tyrannosauroid '' Appalachiosaurus''. The snout and other parts of the skull also sported numerous
foramina In anatomy and osteology, a foramen (; : foramina, or foramens ; ) is an opening or enclosed gap within the dense connective tissue (bones and deep fasciae) of extant and extinct amniote animals, typically to allow passage of nerves, arter ...
. According to the 2017 study which described '' D. horneri'', scaly integument as well as tactile sensitivity was correlated with the multiple rows of neurovascular foramina seen in
crocodilians Crocodilia () is an order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorph pseudosuchi ...
and tyrannosaurids. Tyrannosaurids, like their tyrannosauroid ancestors, were
heterodont In anatomy, a heterodont (from Greek, meaning 'different teeth') is an animal which possesses more than a single tooth morphology. Human dentition is heterodont and diphyodont as an example. In vertebrates, heterodont pertains to animals wher ...
s, with premaxillary teeth ''D''-shaped in cross section and smaller than the rest. Unlike earlier tyrannosauroids and most other theropods, the
maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...
ry and mandibular teeth of mature tyrannosaurids are not blade-like but extremely thickened and often circular in cross-section, with some species having reduced serrations. Tooth counts tend to be consistent within species, and larger species tend to have lower tooth counts than smaller ones. For example, ''Alioramus'' had 76 to 78 teeth in its jaws, while ''Tyrannosaurus'' had between 54 and 60. William Abler observed in 2001 that ''Albertosaurus'' tooth serrations resemble a crack in the tooth ending in a round void called an ampulla.Abler, W.L. 2001. A kerf-and-drill model of tyrannosaur tooth serrations. p. 84–89. In: ''Mesozoic Vertebrate Life''. Ed.s Tanke, D. H., Carpenter, K., Skrepnick, M. W. Indiana University Press. Tyrannosaurid teeth were used as holdfasts for pulling
meat Meat is animal Tissue (biology), tissue, often muscle, that is eaten as food. Humans have hunted and farmed other animals for meat since prehistory. The Neolithic Revolution allowed the domestication of vertebrates, including chickens, sheep, ...
off a body, so when a tyrannosaur would have pulled back on a piece of meat, the tension could cause a purely crack-like serration to spread through the tooth. However, the presence of the ampulla would have distributed these forces over a larger
surface area The surface area (symbol ''A'') of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the d ...
, and lessened the risk of damage to the tooth under strain. The presence of incisions ending in voids has parallels in human engineering.
Guitar The guitar is a stringed musical instrument that is usually fretted (with Fretless guitar, some exceptions) and typically has six or Twelve-string guitar, twelve strings. It is usually held flat against the player's body and played by strumming ...
makers use incisions ending in voids to, as Abler describes, "impart alternating regions of flexibility and rigidity" to the wood they work with. The use of a
drill A drill is a tool used for making round holes or driving fasteners. It is fitted with a drill bit for making holes, or a screwdriver bit for securing fasteners. Historically, they were powered by hand, and later mains power, but cordless b ...
to create an "ampulla" of sorts and prevent the propagation of cracks through material is also used to protect
airplane An airplane (American English), or aeroplane (Commonwealth English), informally plane, is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, Propeller (aircraft), propeller, or rocket engine. Airplanes come in a vari ...
surfaces. Abler demonstrated that a plexiglass bar with incisions called "kerfs" and drilled holes was more than 25% stronger than one with only regularly placed incisions. Unlike tyrannosaurs and other theropods, ancient predators like phytosaurs and ''
Dimetrodon ''Dimetrodon'' ( or ; ) is an extinct genus of sphenacodontid synapsid that lived during the Cisuralian (Early Permian) Epoch (geology), epoch of the Permian period, around 295–272 million years ago. With most species measuring long and ...
'' had no adaptations to prevent the crack-like serrations of their teeth from spreading when subjected to the forces of feeding.


Postcranial skeleton

The skull was perched at the end of a thick, ''S''-shaped neck, and a long, heavy tail acted as a
counterweight A counterweight is a weight (object), weight that, by applying an opposite force, provides balance and stability of a machine, mechanical system. The purpose of a counterweight is to make lifting the load faster and more efficient, which saves e ...
to balance out the head and torso, with the
center of mass In physics, the center of mass of a distribution of mass in space (sometimes referred to as the barycenter or balance point) is the unique point at any given time where the weight function, weighted relative position (vector), position of the d ...
over the hips. Tyrannosaurids are known for their proportionately very small two-fingered forelimbs, although remnants of a
vestigial Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...
third digit are sometimes found. bstract only/ref> ''Tarbosaurus'' had the shortest forelimbs compared to its body size, while ''Daspletosaurus'' had the longest. Tyrannosaurids walked exclusively on their hindlimbs, so their leg bones were massive. In contrast to the forelimbs, the hindlimbs were longer compared to body size than almost any other theropods. Juveniles and even some smaller adults, like more basal tyrannosauroids, had longer
tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...
e than femora, a characteristic of
cursorial A cursorial organism is one that is adapted specifically to run. An animal can be considered cursorial if it has the ability to run fast (e.g. cheetah) or if it can keep a constant speed for a long distance (high endurance). "Cursorial" is often ...
(fast-running) dinosaurs like ornithomimids. Larger adults had leg proportions characteristic of slower-moving animals, but not to the extent seen in other large theropods like abelisaurids or carnosaurs. The third metatarsals of tyrannosaurids were pinched between the second and fourth metatarsals, forming a structure known as the arctometatarsus. Tyrannosaurids also had large preserved leg muscle attachments and low rotational
inertia Inertia is the natural tendency of objects in motion to stay in motion and objects at rest to stay at rest, unless a force causes the velocity to change. It is one of the fundamental principles in classical physics, and described by Isaac Newto ...
relative to their body mass, indicating that they could turn more quickly than other large theropods. It is unclear when the arctometatarsus first evolved; it was not present in the earliest tyrannosauroids like '' Dilong'', but was found in the later '' Appalachiosaurus''. This structure also characterized troodontids, ornithomimids and caenagnathids, but its absence in the earliest tyrannosauroids indicates that it was acquired by
convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...
.


Soft tissue reconstruction

A comparative analysis of the teeth suggests that tyrannosaurids, as well as the other large theropods, had lips that protected their teeth from external damage. This anatomical feature gave these animals more visual resemblance to
lepidosaurs The Lepidosauria (, from Greek meaning ''scaled lizards'') is a Order (biology), superorder or Class (biology), subclass of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata also includes Lizard, lizards and Snake, snakes. Sq ...
than to closely related crocodilians.


Classification

The name Deinodontidae was coined by
Edward Drinker Cope Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontology, paleontologist, comparative anatomy, comparative anatomist, herpetology, herpetologist, and ichthyology, ichthyologist. Born to a wealthy Quaker fam ...
in 1866 for this family, and continued to be used in place of the newer name Tyrannosauridae through the 1960s. The type genus of the Deinodontidae is '' Deinodon'', which was named after isolated teeth from
Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...
. However, in a 1970 review of North American tyrannosaurs,
Dale Russell Dale Alan Russell (27 December 1937 – 21 December 2019) was an American-Canadian geologist and palaeontologist. Throughout his career Russell worked as the Curator of Fossil Vertebrates at the Canadian Museum of Nature, Research Professor at ...
concluded that ''Deinodon'' was not a valid taxon, and used the name Tyrannosauridae in place of Deinodontidae, stating that this was in accordance with
ICZN The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals. It is also informally known as the ICZN Code, for its formal author, t ...
rules. Therefore, Tyrannosauridae is preferred by modern experts. A petition to officially conserve the family Tyrannosauridae and suppress the family Deinodontidae was submitted to the
International Commission on Zoological Nomenclature The International Commission on Zoological Nomenclature (ICZN) is an organization dedicated to "achieving stability and sense in the scientific naming of animals". Founded in 1895, it currently comprises 26 commissioners from 20 countries. Orga ...
(ICZN) in 2020, which was approved in 2024. ''Tyrannosaurus'' was named by
Henry Fairfield Osborn Henry Fairfield Osborn, Sr. (August 8, 1857 – November 6, 1935) was an American paleontologist, geologist and eugenics advocate. He was professor of anatomy at Columbia University, president of the American Museum of Natural History for 25 y ...
in 1905, along with the family Tyrannosauridae. The name is derived from the
Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
words ''τυραννος'' (') ('tyrant') and (') ('lizard'). The very common
suffix In linguistics, a suffix is an affix which is placed after the stem of a word. Common examples are case endings, which indicate the grammatical case of nouns and adjectives, and verb endings, which form the conjugation of verbs. Suffixes can ca ...
''-idae'' is normally appended to
zoological Zoology ( , ) is the scientific study of animals. Its studies include the anatomy, structure, embryology, Biological classification, classification, Ethology, habits, and distribution of all animals, both living and extinction, extinct, and ...
family names and is derived from the Greek suffix ''-ιδαι'' ''-'', which indicates a plural noun.


Taxonomy

Tyrannosauridae is a
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
in rank-based
Linnaean taxonomy Linnaean taxonomy can mean either of two related concepts: # The particular form of biological classification (taxonomy) set up by Carl Linnaeus, as set forth in his ''Systema Naturae'' (1735) and subsequent works. In the taxonomy of Linnaeus th ...
, within the superfamily Tyrannosauroidea and the
suborder Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized ...
Theropoda Theropoda (; from ancient Greek iktionary:θηρίον, , (''therion'') "wild beast"; wiktionary:πούς, , wiktionary:ποδός, (''pous, podos'') "foot" is one of the three major groups (Clade, clades) of Dinosaur, dinosaurs, alon ...
. Tyrannosauridae is uncontroversially divided into two subfamilies. Albertosaurinae comprises the North American genera ''
Albertosaurus ''Albertosaurus'' (; meaning "Alberta lizard") is a genus of large tyrannosaurid theropod dinosaur that lived in northwestern North America during the early to middle Maastrichtian age of the Late Cretaceous period, about 71 million yea ...
'' and ''
Gorgosaurus ''Gorgosaurus'' ( ; ) is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period (Campanian), between about 76.5 and 75 million years ago. Fossil remains have been found in the Ca ...
'', while Tyrannosaurinae includes '' Daspletosaurus'', ''
Teratophoneus ''Teratophoneus'' ("monstrous murderer"; Greek: ''teras'', "monster" and ''phoneus'', "murderer") is a genus of Tyrannosaurinae, tyrannosaurine Theropoda, theropod dinosaur that lived during the late Campanian age of the Late Cretaceous period, ...
'', ''
Bistahieversor ''Bistahieversor'' (meaning "Bistahi destroyer"), also known as the "Bisti Beast", is a genus of basal Eutyrannosauria, eutyrannosaurian Theropoda, theropod dinosaur. The genus contains only a single known species, ''B. sealeyi'', described in 2 ...
'', '' Tarbosaurus'', '' Nanuqsaurus'', ''
Zhuchengtyrannus ''Zhuchengtyrannus'' (meaning "Zhucheng tyrant") is a genus of Tyrannosauridae, tyrannosaurid theropod dinosaur known from the Campanian stage of the Late Cretaceous of Shandong Province, China. It belongs to the subfamily Tyrannosaurinae, and co ...
'', and ''
Tyrannosaurus ''Tyrannosaurus'' () is a genus of large theropod dinosaur. The type species ''Tyrannosaurus rex'' ( meaning 'king' in Latin), often shortened to ''T. rex'' or colloquially t-rex, is one of the best represented theropods. It lived througho ...
'' itself. Some authors include the species ''Gorgosaurus libratus'' in the genus ''Albertosaurus'' and ''Tarbosaurus bataar'' in the genus ''Tyrannosaurus'', while others prefer to retain ''Gorgosaurus'' and ''Tarbosaurus'' as separate genera. Albertosaurines are characterized by more slender builds, lower skulls, and proportionately longer
tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...
e than tyrannosaurines. In tyrannosaurines, the sagittal crest on the parietals continues forward onto the frontals. In 2014, Lü Junchang ''et al.'' described the Alioramini as a
tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...
within the Tyrannosauridae containing the genera '' Alioramus'' and '' Qianzhousaurus''. Their phylogenetic analysis indicated that the tribe was located at the base of the Tyrannosaurinae. Some authors, such as George Olshevsky and Tracy Ford, have created other subdivisions or tribes for various combinations of tyrannosaurids within the subfamilies. However, these have not been phylogenetically defined, and usually consisted of genera that are now considered synonymous with other genera or species. Additional subfamilies have been named for more fragmentary genera, including
Aublysodon ''Aublysodon'' (“backwards-flowing tooth") is a dubious genus of carnivorous dinosaurs known only from the Judith River Formation in Montana, which has been dated to the late Campanian age of the late Cretaceous period (about 75 million years ...
tinae and Deinodontinae. However, the genera ''
Aublysodon ''Aublysodon'' (“backwards-flowing tooth") is a dubious genus of carnivorous dinosaurs known only from the Judith River Formation in Montana, which has been dated to the late Campanian age of the late Cretaceous period (about 75 million years ...
'' and '' Deinodon'' are usually considered '' nomina dubia'', so they and their eponymous subfamilies are usually excluded from taxonomies of tyrannosaurids. An additional tyrannosaurid, '' Raptorex'', was initially described as a more primitive tyrannosauroid, but likely represents a juvenile tyrannosaurine similar to ''Tarbosaurus''. However, as it is known only from a juvenile specimen, it is also currently considered a ''nomen dubium''. However, Thomas Carr maintains its validity and finds it to be similar to tyrannosaurines.


Phylogeny

With the advent of phylogenetic taxonomy in vertebrate paleontology, Tyrannosauridae has been given several explicit definitions. The original was produced by
Paul Sereno Paul Callistus Sereno (born October 11, 1957) is a professor of paleontology at the University of Chicago who has discovered several new dinosaur species on several continents, including at sites in Inner Mongolia, Argentina, Morocco and Niger. ...
in 1998, and included all tyrannosauroids closer to Tyrannosaurus than to either '' Alectrosaurus'', ''
Aublysodon ''Aublysodon'' (“backwards-flowing tooth") is a dubious genus of carnivorous dinosaurs known only from the Judith River Formation in Montana, which has been dated to the late Campanian age of the late Cretaceous period (about 75 million years ...
'' or '' Nanotyrannus''. However, ''Nanotyrannus'' is often considered to be a juvenile ''Tyrannosaurus rex'', while ''Aublysodon'' is usually regarded as a ''
nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium,'' it may be impossible to determine whether a ...
'' unsuitable for use in the definition of a
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
. Definitions since then have been based on more well-established genera. In 2001,
Thomas R. Holtz Thomas Richard Holtz Jr. (born September 13, 1965) is an American vertebrate palaeontologist, author, and principal lecturer at the University of Maryland, College Park, University of Maryland's Department of Geology. He has published extensively ...
Jr. published a
cladistic Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...
analysis of the Tyrannosauridae. He concluded that there were two
subfamilies In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zool ...
: the more primitive Aublysodontinae, characterized by unserrated premaxillary
teeth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...
; and the Tyrannosaurinae. The Aublysodontinae included ''Aublysodon'', the " Kirtland ''Aublysodon''", and '' Alectrosaurus''. Holtz also found that '' Siamotyrannus'' exhibited some of the
synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to ...
of the tyrannosauridae, but lay "outside the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
] proper." Later in the same paper, he proposed that Tyrannosauridae be defined as "all descendants of the most recent common ancestor of ''Tyrannosaurus'' and ''Aublysodon''". He also criticized definitions previously proposed by other workers, like one proposed by
Paul Sereno Paul Callistus Sereno (born October 11, 1957) is a professor of paleontology at the University of Chicago who has discovered several new dinosaur species on several continents, including at sites in Inner Mongolia, Argentina, Morocco and Niger. ...
, that the Tyrannosauridae was "all taxa closer to "Tyrannosaurus" than to ''Alectrosaurus'', ''Aublysodon'', and '' Nanotyrannus''". Holtz observed that since ''Nanotyrannus'' was probably a misidentified ''T. rex'' juvenile, Sereno's proposed definition would have the family Tyrannosauridae as a subtaxon of the genus ''Tyrannosaurus''. Further, his proposed definition of the subfamily Tyrannosaurinae would also be limited to ''Tyrannosaurus''.Holtz, TR, Jr. (2001), The phylogeny and taxonomy of the Tyrannosauridae in K Carpenter & D Tanke ds. Mesozoic Vertebrate Life. Indiana Univ. Press, pp. 64-83. A 2003 attempt by Christopher Brochu included ''
Albertosaurus ''Albertosaurus'' (; meaning "Alberta lizard") is a genus of large tyrannosaurid theropod dinosaur that lived in northwestern North America during the early to middle Maastrichtian age of the Late Cretaceous period, about 71 million yea ...
'', '' Alectrosaurus'', '' Alioramus'', '' Daspletosaurus'', ''
Gorgosaurus ''Gorgosaurus'' ( ; ) is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period (Campanian), between about 76.5 and 75 million years ago. Fossil remains have been found in the Ca ...
'', '' Tarbosaurus'' and ''Tyrannosaurus'' in the definition. Holtz redefined the clade in 2004 to use all of the above as specifiers except for ''Alioramus'' and ''Alectrosaurus'', which his analysis could not place with certainty. However, in the same paper, Holtz also provided a completely different definition, including all theropods more closely related to ''Tyrannosaurus'' than to ''Eotyrannus''. The most recent definition is that of Sereno in 2005, which defined Tyrannosauridae as the least inclusive clade containing ''Albertosaurus'', ''Gorgosaurus'' and ''Tyrannosaurus''.
Cladistic Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...
analyses of tyrannosaurid
phylogeny A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or Taxon, taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, M ...
often find ''Tarbosaurus'' and ''Tyrannosaurus'' to be
sister taxa In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...
, with ''Daspletosaurus'' more basal than either. A close relationship between ''Tarbosaurus'' and ''Tyrannosaurus'' is supported by numerous skull features, including the pattern of sutures between certain bones, the presence of a crescent-shaped crest on the postorbital bone behind each eye, and a very deep maxilla with a noticeable downward curve on the lower edge, among others. An alternative
hypothesis A hypothesis (: hypotheses) is a proposed explanation for a phenomenon. A scientific hypothesis must be based on observations and make a testable and reproducible prediction about reality, in a process beginning with an educated guess o ...
was presented in a 2003 study by Phil Currie and colleagues, which found weak support for ''Daspletosaurus'' as a basal member of a
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
also including ''Tarbosaurus'' and ''Alioramus'', both from Asia, based on the absence of a bony prong connecting the nasal and lacrimal bones. ''Alioramus'' was found to be the closest relative of ''Tarbosaurus'' in this study, based on a similar pattern of stress distribution in the skull. A related study also noted a locking mechanism in the lower jaw shared between the two genera. In a separate paper, Currie noted the possibility that ''Alioramus'' might represent a juvenile ''Tarbosaurus'', but stated that the much higher tooth count and more prominent nasal crests in ''Alioramus'' suggest it is a distinct genus. Similarly, Currie uses the high tooth count of '' Nanotyrannus'' to suggest that it may be a distinct genus, rather than a juvenile ''Tyrannosaurus'' as most other experts believe. However, the discovery and description of '' Qianzhousaurus'' reveals that ''Alioramus'' is not a close relation to ''Tarbosaurus'', instead belonging to a newly described tribe of tyrannosaurids; the Alioramini. ''Qianzhousaurus'' further reveals that similar long-snouted tyrannosaurids were widely distributed throughout Asia and would have shared the same environment while avoiding competition with larger and more robust tyrannosaurines by hunting different prey.


Paleobiology


Growth

Paleontologist Gregory Erickson and colleagues have studied the growth and life history of tyrannosaurids. Analysis of bone
histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology that studies the microscopic anatomy of biological tissue (biology), tissues. Histology is the microscopic counterpart to gross anatomy, which looks at large ...
can determine the age of a specimen when it died. Growth rates can be examined when the age of various individuals are plotted against their size on a graph. Erickson has shown that after a long time as juveniles, tyrannosaurs underwent tremendous
growth spurt Human height or stature is the distance from the bottom of the feet to the top of the head in a human body, standing erect. It is measured using a stadiometer, in centimetres when using the metric system or SI system, or feet and inches when u ...
s for about four years midway through their lives. After the rapid growth phase ended with
sexual maturity Sexual maturity is the capability of an organism to reproduce. In humans, it is related to both puberty and adulthood. ''Puberty'' is the biological process of sexual maturation, while ''adulthood'', the condition of being socially recognized ...
, growth slowed down considerably in adult animals. A tyrannosaurid growth curve is S-shaped, with the maximum growth rate of individuals around 14 years of age. The smallest known ''Tyrannosaurus rex'' individual ( LACM 28471, the "Jordan theropod") is estimated to have weighed only at only 2 years old, while the largest, such as FMNH PR2081 (" Sue"), most likely weighed about , estimated to have been 28 years old, an age which may have been close to the maximum for the species. and corresponding body mass estimates ranged from 29.9 to 5654 kg ''T. rex'' juveniles remained under until approximately 14 years of age, when body size began to increase dramatically. During this rapid growth phase, a young ''T. rex'' would gain an average of a year for the next four years. This slowed after 16 years, and at 18 years of age, the curve plateaus again, indicating that growth slowed dramatically. For example, only separated the 28-year-old "Sue" from a 22-year-old
Canadian Canadians () are people identified with the country of Canada. This connection may be residential, legal, historical or cultural. For most Canadians, many (or all) of these connections exist and are collectively the source of their being ''C ...
specimen ( RTMP 81.12.1). This sudden change in growth rate may indicate physical maturity, a hypothesis that is supported by the discovery of medullary tissue in the
femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...
of an 18-year-old ''T. rex'' from Montana ( MOR 1125, also known as "B-rex"). Medullary tissue is found only in female birds during ovulation, indicating that "B-rex" was of reproductive age. Other tyrannosaurids exhibit extremely similar growth curves, although with lower growth rates corresponding to their lower adult sizes. Compared to albertosaurines, ''Daspletosaurus'' showed a faster growth rate during the rapid growth period due to its higher adult weight. The maximum growth rate in ''Daspletosaurus'' was per year, based on a mass estimate of in adults. Other authors have suggested higher adult weights for ''Daspletosaurus''; this would change the magnitude of the growth rate, but not the overall pattern. The youngest known ''Albertosaurus'' is a two-year-old discovered in the Dry Island bonebed, which would have weighed about and measured slightly more than in length. The specimen from the same quarry is the oldest and largest known, at 28 years of age. The fastest growth rate is estimated to occur around 12–16 years of age, reaching per year, based on a adult, which is about a fifth of the rate for ''T.-rex''. For ''Gorgosaurus'', the calculated maximum growth rate is about during the rapid growth phase, which is comparable to that of ''Albertosaurus''. The discovery of an embryonic tyrannosaur of an as-yet-unknown genus suggests that tyrannosaurids developed their distinctive skeletal features while developing in the egg. Furthermore, the size of the specimen, a dentary from the lower jaw found in the
Two Medicine Formation The Two Medicine Formation is a geological formation, or rock body, in northwestern Montana and southern Alberta that was deposited between 82.4 Ma and 74.4 Ma, during Campanian (Late Cretaceous) time. It crops out to the east of the Rocky Mountai ...
of Montana in 1983 and a foot claw found in the Horseshoe Canyon Formation in 2018 and described in 2020, suggests that neonate tyrannosaurids were born with skulls the size of a mouse or similarly sized rodents and may have been roughly the size of a small dog at birth. The jaw specimen is believed to have come from an animal roughly while the claw is believed to belong to a specimen measuring around . While eggshells have not been found in association with either specimen, the location where these neonate tyrannosaurids were uncovered suggests these animals were using the same nest sites as other species they lived with and preyed upon. The lack of eggshells associated with these specimens has also opened up speculation to the possibility that tyrannosaurids laid soft-shelled eggs as the genera '' Mussaurus'' and ''
Protoceratops ''Protoceratops'' (; ) is a genus of small protoceratopsid dinosaurs that lived in Asia during the Late Cretaceous, around 75 to 71 million years ago. The genus ''Protoceratops'' includes two species: ''P. andrewsi'' and the larger ''P. hellenik ...
'' are believed to have done. Fossil footprints from the Wapiti Formation suggest that as tyrannosaurids grew, the feet became wider with thicker toes to support their weight. The broader feet suggest that adult tyrannosaurids were slower-moving than their offspring.


Life history

The end of the rapid growth phase suggests the onset of
sexual maturity Sexual maturity is the capability of an organism to reproduce. In humans, it is related to both puberty and adulthood. ''Puberty'' is the biological process of sexual maturation, while ''adulthood'', the condition of being socially recognized ...
in ''Albertosaurus'', although growth continued at a slower rate throughout the animals' lives. Sexual maturation while still actively growing appears to be a shared trait among small and large dinosaurs as well as in large mammals, such as humans and
elephant Elephants are the largest living land animals. Three living species are currently recognised: the African bush elephant ('' Loxodonta africana''), the African forest elephant (''L. cyclotis''), and the Asian elephant ('' Elephas maximus ...
s. This pattern of relatively early sexual maturation differs strikingly from the pattern in birds, which delay their sexual maturity until after they have finished growing. By tabulating the number of specimens of each age group, Erickson and his colleagues were able to draw conclusions about life history in tyranosauridae populations. Their analysis showed that while juveniles were rare in the fossil record, subadults in the rapid growth phase and adults were far more common. Over half of the known ''T. rex'' specimens appear to have died within six years of reaching sexual maturity, a pattern that is also seen in other tyrannosaurs and in some large, long-lived birds and mammals today. These species are characterized by high infant mortality rates, followed by relatively low mortality among juveniles. Mortality increases again following sexual maturity, partly due to the stresses of reproduction. While this could be due to preservation or collection
biases Bias is a disproportionate weight ''in favor of'' or ''against'' an idea or thing, usually in a way that is inaccurate, closed-minded, prejudicial, or unfair. Biases can be innate or learned. People may develop biases for or against an individ ...
, Erickson hypothesized that the difference was due to low mortality among juveniles over a certain size, which is also seen in some modern large mammals, like
elephant Elephants are the largest living land animals. Three living species are currently recognised: the African bush elephant ('' Loxodonta africana''), the African forest elephant (''L. cyclotis''), and the Asian elephant ('' Elephas maximus ...
s. This low mortality may have resulted from a lack of predation, since tyrannosaurs surpassed all contemporaneous predators in size by the age of two. Paleontologists have not found enough ''Daspletosaurus'' remains for a similar analysis, but Erickson notes that the same general trend seems to apply. The tyrannosaurids spent as much as half its life in the juvenile phase before ballooning up to near-maximum size in only a few years. This, along with the complete lack of predators intermediate in size between huge adult tyrannosaurids and other small theropods, suggests these niches may have been filled by juvenile tyrannosaurids. This is seen in modern
Komodo dragon The Komodo dragon (''Varanus komodoensis''), also known as the Komodo monitor, is a large reptile of the monitor lizard family Varanidae that is endemic to the Indonesian islands of Komodo (island), Komodo, Rinca, Flores, Gili Dasami, and Gili ...
s, where hatchlings start off as tree-dwelling
insectivore file:Common brown robberfly with prey.jpg, A Asilidae, robber fly eating a hoverfly An insectivore is a carnivore, carnivorous animal or plant which eats insects. An alternative term is entomophage, which can also refer to the Entomophagy ...
s and slowly mature into massive
apex predator An apex predator, also known as a top predator or superpredator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the hig ...
s capable of taking down large vertebrates. For example, ''Albertosaurus'' have been found in aggregations that some have suggested to represent mixed-age packs.


Locomotion

Locomotion abilities are best studied for ''Tyrannosaurus'', and there are two main issues concerning this: how well it could turn; and what its maximum straight-line speed was likely to have been. ''Tyrannosaurus'' may have been slow to turn, possibly taking one to two seconds to turn only 45° – an amount that humans, being vertically oriented and tail-less, can spin in a fraction of a second. The cause of the difficulty is
rotational inertia The moment of inertia, otherwise known as the mass moment of inertia, angular/rotational mass, second moment of mass, or most accurately, rotational inertia, of a rigid body is defined relatively to a rotational axis. It is the ratio between ...
, since much of ''Tyrannosaurus''s mass was some distance from its center of gravity, like a human carrying a heavy timber. Scientists have produced a wide range of maximum speed estimates, mostly around , but a few as low as , and a few as high as . Researchers have to rely on various estimating techniques because, while there are many tracks of very large theropods walking, so far none have been found of very large theropods running—and this absence ''may'' indicate that they did not run. Jack Horner and Don Lessem argued in 1993 that ''Tyrannosaurus'' was slow and probably could not run (no airborne phase in mid-stride). However, Holtz (1998) concluded that tyrannosaurids and their close relatives were the fastest large theropods. Christiansen (1998) estimated that the leg bones of ''Tyrannosaurus'' were not significantly stronger than those of elephants, which are relatively limited in their top speed and never actually run (there is no airborne phase), and hence proposed that the dinosaur's maximum speed would have been about , which is about the speed of a human sprinter. Farlow and colleagues (1995) have argued that a 6- to 8-ton ''Tyrannosaurus'' would have been critically or even fatally injured if it had fallen while moving quickly, since its torso would have slammed into the ground at a deceleration of 6 ''g'' (six times the acceleration due to gravity, or about 60 metres/s2) and its tiny arms could not have reduced the impact. However,
giraffe The giraffe is a large Fauna of Africa, African even-toed ungulate, hoofed mammal belonging to the genus ''Giraffa.'' It is the Largest mammals#Even-toed Ungulates (Artiodactyla), tallest living terrestrial animal and the largest ruminant on ...
s have been known to gallop at , despite the risk that they might break a leg or worse, which can be fatal even in a "safe" environment such as a zoo. Thus it is quite possible that ''Tyrannosaurus'' also moved fast when necessary and had to accept such risks; this scenario has been studied for ''Allosaurus'' too. catalogues the injuries of the ''
Allosaurus ''Allosaurus'' ( ) is an extinct genus of theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period ( Kimmeridgian to late Tithonian ages). The first fossil remains that could definitively be ascribed to th ...
'' known as " Big Al" - at least one was attributed to a fall.
Most recent research on ''Tyrannosaurus'' locomotion does not narrow down speeds further than a range from , i.e. from walking or slow running to moderate-speed running.Hajdul, R. (1997). Tendons. ''Dinosaur Cards''. Orbis Publishing Ltd. D36044311. A computer model study in 2007 estimated running speeds, based on data taken directly from fossils, and claimed that ''T. rex'' had a top running speed of . This may be a preliminary version of Sellers, W. I., Manning, P.L., Crompton, R.H. and Codd, J.R.,. (2007), "Exploring elastic energy storage effects in bipedal locomotion using evolutionary robotics", ''Journal of Biomechanics'', in-review (Probably a juvenile individual.) Studies by Eric Snively ''et al.,'' published in 2019 indicate that tyrannosaurids such as ''Tarbosaurus'' and ''Tyrannosaurus'' itself were more manoeuvrable than allosauroids of comparable size due to low rotational inertia compared to their body mass combined with large leg muscles. As a result, it is hypothesized that tyrannosaurids were capable of making relatively quick turns and could likely pivot their bodies more quickly when close to their prey, or that while turning, they could "pirouette" on a single planted foot while the alternating leg was held out in a suspended swing during pursuit. The results of this study potentially could shed light on how agility could have contributed to the success of tyrannosaurid evolution. Additionally, a 2020 study indicates that tyrannosaurids were exceptionally efficient walkers. Studies by Dececchi ''et al.'', compared the leg proportions, body mass, and the gaits of more than 70 species of theropod dinosaurs including tyrannosaurids. The research team then applied a variety of methods to estimate each dinosaur's top speed when running as well as how much energy each dinosaur expended while moving at more relaxed speeds such as when walking. Among smaller to medium-sized species such as dromaeosaurids, longer legs appear to be an adaptation for faster running, in line with previous results by other researchers. But for theropods weighing over , top running speed is limited by body size, so longer legs instead were found to have correlated with low-energy walking. The results of the study further indicated that smaller theropods evolved long legs for speed as a means to both aid in hunting and escape from larger predators while larger predatory theropods that evolved long legs did so to reduce the energy costs and increase foraging efficiency, as they were freed from the demands of predation pressure due to their role as apex predators. Compared to more basal groups of theropods in the study, tyrannosaurids showed a marked increase in foraging efficiency due to reduced energy expenditures during hunting and scavenging. This likely resulted in tyrannosaurs having a reduced need for hunting forays and requiring less food to sustain themselves as a result. Additionally, the research, in conjunction with studies that show tyrannosaurs were more agile than other large-bodied theropods, indicates they were quite well-adapted to a long-distance stalking approach followed by a quick burst of speed to go for the kill. Analogies can be noted between tyrannosaurids and modern wolves as a result, supported by evidence that at least some tyrannosaurids such as ''Albertosaurus'' were hunting in group settings.


Integument

An ongoing debate in the paleontological community surrounds the extent and nature of tyrannosaurid integumentary covering. Long filamentous structures have been preserved along with skeletal remains of numerous coelurosaurs from the Early Cretaceous
Yixian Formation The Yixian Formation (; formerly Romanization of Chinese, transcribed as Yihsien Formation or Yixiang Formation) is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans the Barremian stage of the Early Cretaceous. I ...
and other nearby geological formations from
Liaoning ) , image_skyline = , image_alt = , image_caption = Clockwise: Mukden Palace in Shenyang, Xinghai Square in Dalian, Dalian coast, Yalu River at Dandong , image_map = Liaoning in China (+all claims hatched).svg , ...
, China. These filaments have usually been interpreted as "protofeathers," homologous with the branched feathers found in birds and some non-avian theropods, although other hypotheses have been proposed. A skeleton of ''Dilong'' was described in 2004 that included the first example of "protofeathers" in a tyrannosauroid. Similarly to
down feather The down of birds is a layer of fine feathers found under the tougher exterior feathers. Very young birds are clad only in down. Powder down is a specialized type of down found only in a few groups of birds. Down is a fine thermal insulator and p ...
s of modern birds, the "protofeathers" found in ''Dilong'' were branched but not pennaceous, and may have been used for insulation. The discovery and description of the feathered tyrannosauroid '' Yutyrannus'' in 2012 indicates the possibility large tyrannosaurids were also feathered as adults. Based on the principle of phylogenetic bracketing, it was predicted that tyrannosaurids might also possess such feathering. However, a study in 2017 published by a team of researchers in Biology Letters described tyrannosaurid skin impressions collected in Alberta, Montana, and Mongolia, which came from five genera (''Tyrannosaurus'', ''Albertosaurus'', ''Gorgosaurus'', ''Daspletosaurus'' and ''Tarbosaurus''). Although the skin impressions are small, they are widely dispersed across the post-cranium, being collectively located on the abdomen, thoracic region, ilium, pelvis, tail, and neck. They show a tight pattern of fine, non-overlapping pebbly scales (which co-author Scott Persons compared to those seen on the flanks of a crocodile) and preserve no hints of feathering. The basic texture is composed of tiny "basement scales" approximately 1 to 2 mm in diameter, with some impressions showing 7 mm "feature scales" interspersed between them. Additional scales can be seen in tyrannosaurid footprints. Studies find that the facial integument of tyrannosaurids had scales on the dentary and maxilla, cornified epidermis and armor-like skin on the subordinate regions. Bell ''et al.'' performed an ancestral character reconstruction based on what is known about integument distribution in tyrannosauroids. Despite an 89% probability that tyrannosauroids started out with feathers, they determined that scaly tyrannosaurids have a 97% probability of being true. The data "provides compelling evidence of an entirely squamous covering in Tyrannosaurus," the team wrote, although they conceded that plumage may have still been present on the dorsal region where skin impressions haven't been found yet. Bell ''et al.'' hypothesizes that the scale impressions of tyrannosaurids are possibly reticula which are secondarily derived from feathers though evidence is needed to support this. However, others argue that this is because of taphonomic bias in tyrannosaurids. It has yet to be determined why such an integumentary change might have occurred. A precedent for feather loss can be seen in other dinosaur groups such as
ornithischia Ornithischia () is an extinct clade of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek ...
ns, in which filamentous structures were lost, and scales reappeared. Although gigantism has been suggested as a mechanism, Phil R. Bell, who co-authored the study, noted that the feathered ''Yutyrannus'' overlapped in size with ''Gorgosaurus'' and ''Albertosaurus''. "The problem here is that we have big tyrannosaurs, some with feathers, some without that live in pretty similar climates. So what's the reason for this difference? We really don't know."


Vision

The eye-sockets of ''Tyrannosaurus'' are positioned so that the eyes would point forward, giving them
binocular vision Binocular vision is seeing with two eyes. The Field_of_view, field of view that can be surveyed with two eyes is greater than with one eye. To the extent that the visual fields of the two eyes overlap, #Depth, binocular depth can be perceived. Th ...
slightly better than that of modern
hawk Hawks are birds of prey of the family Accipitridae. They are very widely distributed and are found on all continents, except Antarctica. The subfamily Accipitrinae includes goshawks, sparrowhawks, sharp-shinned hawks, and others. This ...
s. While predatory theropods in general had binocular vision directly in front of their skull, tyrannosaurs had a significantly larger area of overlap.
Jack Horner Jack Horner may refer to: *"Little Jack Horner", a nursery rhyme People * Jack Horner (activist) (born 1922), Australian author and activist in the Aboriginal-Australian Fellowship * Jack Horner (baseball) (1863–1910), American professional ba ...
also pointed out that the tyrannosaur lineage had a history of steadily improving binocular vision. It is hard to see how
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the Heredity, heritable traits characteristic of a population over generation ...
would have favored this long-term trend if tyrannosaurs had been pure scavengers, which would not have needed the advanced
depth perception Depth perception is the ability to perceive distance to objects in the world using the visual system and visual perception. It is a major factor in perceiving the world in three dimensions. Depth sensation is the corresponding term for non-hum ...
that
stereoscopic vision Binocular vision is seeing with two eyes, which increases the size of the visual field. If the visual fields of the two eyes overlap, binocular depth can be seen. This allows objects to be recognized more quickly, camouflage to be detected, spa ...
provides. In modern animals, binocular vision is found mainly in predators (the principal exceptions are
primate Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...
s, which need it for leaping from branch to branch). Unlike ''Tyrannosaurus'', ''Tarbosaurus'' had a narrower skull more typical of other tyrannosaurids in which the eyes faced primarily sideways. All of this suggests that ''Tarbosaurus'' relied more on its senses of smell and hearing than on its eyesight. In ''Gorgosaurus'' specimens, the
eye socket In anatomy, the orbit is the cavity or socket/hole of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents. In the adult human, the volume of the orbit is ...
was circular rather than oval or keyhole-shaped as in other tyrannosaurid genera. In ''Daspletosaurus'', this was a tall oval, somewhere in between the circular shape seen in ''Gorgosaurus'' and the 'keyhole' shape of ''Tyrannosaurus''.


Facial sensitivity

Based on comparisons of bone texture of '' Daspletosaurus'' with extant
crocodilians Crocodilia () is an order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorph pseudosuchi ...
, a detailed study in 2017 by Thomas D. Carr ''et al.'' found that tyrannosaurs had large, flat
scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number ...
on their snouts. At the center of these
scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number ...
were small
keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. It is the key structural material making up Scale (anatomy), scales, hair, Nail (anatomy), nails, feathers, horn (anatomy), horns, claws, Hoof, hoove ...
ised patches. In
crocodilians Crocodilia () is an order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorph pseudosuchi ...
, such patches cover bundles of sensory neurons that can detect mechanical, thermal and chemical
stimuli A stimulus is something that causes a physiological response. It may refer to: *Stimulation **Stimulus (physiology), something external that influences an activity **Stimulus (psychology), a concept in behaviorism and perception *Stimulus (economi ...
. They proposed that tyrannosaurs probably also had bundles of sensory neurons under their facial
scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number ...
and may have used them to identify objects, measure the
temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...
of their nests and gently pick-up
egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...
s and hatchlings.


Bony crests

Bony crests are found on the skulls of many theropods, including many tyrannosaurids. '' 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''. 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 The ''postorbital'' is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some ...
. These head crests may have been used for display, perhaps for species recognition or
courtship Courtship is the period wherein some couples get to know each other prior to a possible marriage or committed romantic, ''de facto'' relationship. Courtship traditionally may begin after a betrothal and may conclude with the celebration of marri ...
behavior.


Thermoregulation

''Tyrannosaurus'', like most dinosaurs, was long thought to have an
ectotherm An ectotherm (), more commonly referred to as a "cold-blooded animal", is an animal in which internal physiological sources of heat, such as blood, are of relatively small or of quite negligible importance in controlling body temperature.Dav ...
ic ("cold-blooded") reptilian
metabolism Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the co ...
but was challenged by scientists like Robert T. Bakker and John Ostrom in the early years of the " Dinosaur Renaissance", beginning in the late 1960s. ''Tyrannosaurus rex'' itself was claimed to have been
endothermic An endothermic process is a chemical or physical process that absorbs heat from its surroundings. In terms of thermodynamics, it is a thermodynamic process with an increase in the enthalpy (or internal energy ) of the system.Oxtoby, D. W; Gillis, ...
("warm-blooded"), implying a very active lifestyle. Since then, several paleontologists have sought to determine the ability of ''Tyrannosaurus'' to
regulate Regulate may refer to: * Regulation Regulation is the management of complex systems according to a set of rules and trends. In systems theory, these types of rules exist in various fields of biology and society, but the term has slightly diff ...
its body
temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...
. Histological evidence of high growth rates in young ''T. rex'', comparable to those of mammals and birds, may support the hypothesis of a high metabolism. Growth curves indicate that, as in mammals and birds, ''T. rex'' growth was limited mostly to immature animals, rather than the
indeterminate growth In biology and botany, indeterminate growth is growth that is not terminated, in contrast to determinate growth that stops once a genetically predetermined structure has completely formed. Thus, a plant that grows and produces flowers and fruit ...
seen in most other
vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...
s. It has been indicated that the temperature difference may have been no more than 4 to 5 °C (7 to 9 °F) between the vertebrae of the torso and the
tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...
of the lower leg. This small temperature range between the body core and the extremities was claimed by paleontologist Reese Barrick and geochemist William Showers to indicate that ''T. rex'' maintained a constant internal body temperature ( homeothermy) and that it enjoyed a metabolism somewhere between ectothermic reptiles and endothermic mammals. Later they found similar results in ''
Giganotosaurus ''Giganotosaurus'' ( ) is a genus of large theropod dinosaur that lived in what is now Argentina, during the early Cenomanian age of the Late Cretaceous period (geology), period, approximately 99.6 to 95 million years ago. The holotype specim ...
'' specimens, who lived on a different continent and tens of millions of years earlier in time. Even if ''Tyrannosaurus rex'' does exhibit evidence of homeothermy, it does not necessarily mean that it was endothermic. Such thermoregulation may also be explained by
gigantothermy Gigantothermy (sometimes called ectothermic homeothermy or inertial homeothermy) is a phenomenon with significance in biology and paleontology, whereby large, bulky ectothermic animals are more easily able to maintain a constant, relatively high bo ...
, as in some living
sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerh ...
s.


Paleoecology


Coexistence of ''Daspletosaurus'' and ''Gorgosaurus''

In the Dinosaur Park Formation, ''Gorgosaurus'' lived alongside a rarer species of the tyrannosaurine ''Daspletosaurus''. This is one of the few examples of two tyrannosaur genera coexisting. Similarly sized predators in modern predator
guilds A guild ( ) is an association of artisans and merchants who oversee the practice of their craft/trade in a particular territory. The earliest types of guild formed as organizations of tradespeople belonging to a professional association. They so ...
are separated into different
ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of Resource (biology), resources an ...
s by anatomical, behavioral or geographical differences that limit competition.
Niche differentiation In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of resources and competitors (for e ...
between the Dinosaur Park tyrannosaurids is not well understood. In 1970, Dale Russell hypothesized that the more common ''Gorgosaurus'' actively hunted fleet-footed hadrosaurs, while the rarer and more troublesome
ceratopsia Ceratopsia or Ceratopia ( or ; Ancient Greek, Greek: "horned faces") is a group of herbivore, herbivorous, beaked dinosaurs that thrived in what are now North America, Asia and Europe, during the Cretaceous Period (geology), Period, although ance ...
ns and
ankylosauria Ankylosauria is a group of herbivorous dinosaurs of the clade Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful limbs ...
ns (horned and heavily
armoured Armour (Commonwealth English) or armor (American English; see spelling differences) is a covering used to protect an object, individual, or vehicle from physical injury or damage, especially direct contact weapons or projectiles during combat ...
dinosaurs) were left to the more heavily built '' Daspletosaurus''. However, a specimen of ''Daspletosaurus'' ( OTM 200) from the contemporaneous
Two Medicine Formation The Two Medicine Formation is a geological formation, or rock body, in northwestern Montana and southern Alberta that was deposited between 82.4 Ma and 74.4 Ma, during Campanian (Late Cretaceous) time. It crops out to the east of the Rocky Mountai ...
of Montana preserves the digested remains of a juvenile hadrosaur in its gut region. Unlike some other groups of dinosaurs, neither genus was more common at higher or lower elevations than the other. However, ''Gorgosaurus'' appears more common in northern formations like the Dinosaur Park, with species of ''Daspletosaurus'' more abundant to the south. The same pattern is seen in other groups of dinosaurs. Chasmosaurine ceratopsians and hadrosaurine hadrosaurs are also more common in the Two Medicine Formation of Montana and in southwestern North America during the Campanian, while centrosaurines and lambeosaurines dominate in northern latitudes. Holtz has suggested that this pattern indicates shared ecological preferences between tyrannosaurines, chasmosaurines and hadrosaurines. At the end of the later Maastrichtian stage, tyrannosaurines like ''Tyrannosaurus rex'', hadrosaurines like ''
Edmontosaurus ''Edmontosaurus'' ( ) (meaning "lizard from Edmonton"), with the second species often colloquially and historically known as ''Anatosaurus'' or ''Anatotitan'' (meaning "duck lizard" and "giant duck"), is a genus of hadrosaurid (duck-billed) din ...
'' and chasmosaurines like ''
Triceratops ''Triceratops'' ( ; ) is a genus of Chasmosaurinae, chasmosaurine Ceratopsia, ceratopsian dinosaur that lived during the late Maastrichtian age of the Late Cretaceous Period (geology), period, about 68 to 66 million years ago on the island ...
'' were widespread throughout western North America, while albertosaurines and centrosaurines became extinct, and lambeosaurines were rare.


Social behavior

There is limited evidence of social behavior among the tyrannosaurids. Researchers reported that a subadult and a juvenile skeleton were found in the same quarry as the "Sue" specimen, which has been used to support the hypothesis that tyrannosaurs may have lived in social groups of some kind.Guinness World Records Ltd. (2003). ''2003 Guinness World Records''. pg 90. While there is no evidence of gregarious behavior in ''Gorgosaurus'', there is evidence of some pack behavior for ''Albertosaurus'' and ''Daspletosaurus''. A young specimen of the Dinosaur Park ''Daspletosaurus'' species ( TMP 94.143.1) shows bite marks on the face that were inflicted by another tyrannosaur. The bite marks are healed over, indicating that the animal survived the bite. A full-grown Dinosaur Park ''Daspletosaurus'' (TMP 85.62.1) also exhibits tyrannosaur bite marks, showing that attacks to the face were not limited to younger animals. While it is possible that the bites were attributable to other species, intraspecific aggression, including facial biting, is very common among predators. Facial bites are seen in other tyrannosaurs like ''Gorgosaurus'' and ''Tyrannosaurus'', as well as in other theropod genera like '' Sinraptor'' and ''
Saurornitholestes ''Saurornitholestes'' ("lizard-bird thief") is a genus of carnivorous dromaeosaurid theropod dinosaur from the late Cretaceous of Canada (Alberta and Saskatchewan) and the United States (Montana, New Mexico, Alabama, and South Carolina). Two spe ...
''. Darren Tanke and Phil Currie hypothesize that the bites are due to
intraspecific competition Intraspecific competition is an interaction in population ecology, whereby members of the same species compete for limited resources. This leads to a reduction in fitness for both individuals, but the more fit individual survives and is able to ...
for territory or resources, or for dominance within a social group. Evidence that ''Daspletosaurus'' lived in social groups comes from a bonebed found in the Two Medicine Formation of Montana. The bonebed includes the remains of three ''Daspletosaurus'', including a large adult, a small juvenile, and another individual of intermediate size. At least five hadrosaurs are preserved at the same location. Geologic evidence indicates that the remains were not brought together by river currents but that all of the animals were buried simultaneously at the same location. The hadrosaur remains are scattered and bear many marks from tyrannosaur teeth, indicating that the ''Daspletosaurus'' were feeding on the hadrosaurs at the time of death. The cause of death is unknown. Currie speculates that the daspletosaurs formed a
pack Pack or packs may refer to: Music * Packs (band), a Canadian indie rock band * ''Packs'' (album), by Your Old Droog * ''Packs'', a Berner album Places * Pack, Styria, defunct Austrian municipality * Pack, Missouri, United States (US) * ...
, although this cannot be stated with certainty. Other scientists are skeptical of the evidence for social groups in ''Daspletosaurus'' and other large theropods; Brian Roach and Daniel Brinkman have suggested that ''Daspletosaurus'' social interaction would have more closely resembled the modern
Komodo dragon The Komodo dragon (''Varanus komodoensis''), also known as the Komodo monitor, is a large reptile of the monitor lizard family Varanidae that is endemic to the Indonesian islands of Komodo (island), Komodo, Rinca, Flores, Gili Dasami, and Gili ...
, where non-cooperative individuals mob carcasses, frequently attacking and even cannibalizing each other in the process. The Dry Island bonebed discovered by Barnum Brown and his crew contains the remains of 22 ''Albertosaurus'', the most individuals found in one locality of any Cretaceous theropod, and the second-most of any large theropod dinosaur behind the ''
Allosaurus ''Allosaurus'' ( ) is an extinct genus of theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period ( Kimmeridgian to late Tithonian ages). The first fossil remains that could definitively be ascribed to th ...
'' assemblage at the
Cleveland-Lloyd Dinosaur Quarry Jurassic National Monument, at the site of the Cleveland-Lloyd Dinosaur Quarry, well known for containing the densest concentration of Jurassic dinosaur fossils ever found, is a paleontological site located near Cleveland, Utah, in the San Rafa ...
in
Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...
. The group seems to be composed of one very old adult; eight adults between 17 and 23 years old; seven sub-adults undergoing their rapid growth phases at between 12 and 16 years old; and six juveniles between the ages of 2 and 11 years, who had not yet reached the growth phase. The near-absence of
herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...
remains and the similar state of preservation between the many individuals at the ''Albertosaurus'' bonebed quarry led Phil Currie to conclude that the locality was not a predator trap like the
La Brea Tar Pits La Brea Tar Pits comprise an active Paleontological site, paleontological research site in urban Los Angeles. Hancock Park was formed around a group of tar pits where natural Bitumen, asphalt (also called asphaltum, bitumen, or pitch; ''brea'' ...
in
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
, and that all of the preserved animals died at the same time. Currie claims this as evidence of pack behavior.(not printed until 2000) Other scientists are skeptical, observing that the animals may have been driven together by drought, flood or for other reasons. While it generally remains controversial, evidence does exist that supports the theory that at least some tyrannosaurids were social. In
British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...
's Wapiti Formation, a
trackway Historic roads (or historic trails in the US and Canada) are paths or routes that have historical importance due to their use over a period of time. Examples exist from prehistoric times until the early 20th century. They include ancient track ...
composed of the footprints of three individual tyrannosaurids (named as the ichnogenus '' Bellatoripes fredlundi'') was discovered by a local outfitter named Aaron Fredlund and described in the journal PLOS One by Richard McCrea et al. An examination of the trackway found no evidence of one trackway being left long after another had been made, further supporting the hypothesis that three individual tyrannosaurs were traveling together as a group. Further research revealed the animals were traveling at a speed of between and likely had a hip height of around 7 to 9 feet. As three different genera of tyrannosaurids (''Gorgosaurus'', ''Daspletosaurus'', and ''Albertosaurus'', respectively) are known from the formation, it is unknown which genus was the maker of the trackway. Additional evidence in the form of a bone-bed from the Rainbows and Unicorns Quarry in Southern Utah's Kaiparowits Formation described in 2021 attributed to ''
Teratophoneus ''Teratophoneus'' ("monstrous murderer"; Greek: ''teras'', "monster" and ''phoneus'', "murderer") is a genus of Tyrannosaurinae, tyrannosaurine Theropoda, theropod dinosaur that lived during the late Campanian age of the Late Cretaceous period, ...
'' suggests other tyrannosaurids were also social animals. The fossils, consisting of four or possibly five different animals ranging from 4–22 years of age, suggest a mass mortality event, possibly caused by flooding, or less likely by
cyanobacterial toxicosis Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteria's ...
, fire, or drought. The fact that all of the animals preserved seemed to have perished within a short timespan further strengthens the argument for gregarious behavior in tyrannosaurids, with the bone beds of such genera as ''Teratophoneus'', ''Albertosaurus'', ''Tyrannosaurus'' and ''Daspletosaurus'' showcasing suggested social behavior may have been widespread amongst tyrannosauridae in general.


Feeding

Tyrannosaur tooth marks are the most commonly preserved feeding traces of carnivorous dinosaurs. They have been reported from
ceratopsia Ceratopsia or Ceratopia ( or ; Ancient Greek, Greek: "horned faces") is a group of herbivore, herbivorous, beaked dinosaurs that thrived in what are now North America, Asia and Europe, during the Cretaceous Period (geology), Period, although ance ...
ns, hadrosaurs and other tyrannosaurs. Tyrannosaurid bones with tooth marks represent about 2% of known fossils with preserved tooth marks.Jacobsen, A.R. 2001. Tooth-marked small theropod bone: An extremely rare trace. p. 58-63. In: Mesozoic Vertebrate Life. Ed.s Tanke, D. H., Carpenter, K., Skrepnick, M. W. Indiana University Press. Tyrannosaurid teeth were used as holdfasts for pulling
meat Meat is animal Tissue (biology), tissue, often muscle, that is eaten as food. Humans have hunted and farmed other animals for meat since prehistory. The Neolithic Revolution allowed the domestication of vertebrates, including chickens, sheep, ...
off a body, rather than
knife A knife (: knives; from Old Norse 'knife, dirk') is a tool or weapon with a cutting edge or blade, usually attached to a handle or hilt. One of the earliest tools used by humanity, knives appeared at least Stone Age, 2.5 million years ago, as e ...
-like cutting functions.Abler, W.L. 2001. A kerf-and-drill model of tyrannosaur tooth serrations. p. 84-89. In: ''Mesozoic Vertebrate Life''. Ed.s Tanke, D. H., Carpenter, K., Skrepnick, M. W. Indiana University Press. Tooth wear patterns hint that complex head shaking behaviors may have been involved in tyrannosaur feeding. Speculation on the pack-hunting habits of ''Albertosaurus'' were made by a few researchers who suggest that the younger members of the pack may have been responsible for driving their prey towards the adults, who were larger and more powerful, but also slower. Juveniles may also have had different lifestyles than adults, filling predator niches between those of the enormous adults and the smaller contemporaneous theropods, the largest of which were two
orders of magnitude In a ratio scale based on powers of ten, the order of magnitude is a measure of the nearness of two figures. Two numbers are "within an order of magnitude" of each other if their ratio is between 1/10 and 10. In other words, the two numbers are wi ...
smaller than an adult ''Albertosaurus'' in mass. However, as the preservation of behavior in the fossil record is exceedingly rare, these ideas cannot readily be tested. Phil Currie speculates that the ''Daspletosaurus'' formed packs to hunt, although this cannot be stated with certainty. There is no evidence of such gregarious behavior in ''Gorgosaurus''. ot printed until 2000/ref> The debate about whether ''Tyrannosaurus'' was a
predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
or a pure
scavenger Scavengers are animals that consume Corpse decomposition, dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a he ...
is as old as the debate about its locomotion. Lambe (1917) described a good skeleton of ''Tyrannosaurus''s close relative ''Gorgosaurus'' and concluded that it and therefore also ''Tyrannosaurus'' was a pure scavenger, because the ''Gorgosaurus''s teeth showed hardly any wear. This argument is no longer taken seriously, because theropods replaced their teeth quite rapidly. Ever since the first discovery of ''Tyrannosaurus'' most scientists have agreed that it was a predator, although like modern large predators it would have been happy to scavenge or steal another predator's kill if it had the opportunity.Dorey, M. (1997). Tyrannosaurus. ''Dinosaur Cards''. Orbis Publishing Ltd. D36045907. Noted
hadrosaur Hadrosaurids (), also hadrosaurs or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod fami ...
expert
Jack Horner Jack Horner may refer to: *"Little Jack Horner", a nursery rhyme People * Jack Horner (activist) (born 1922), Australian author and activist in the Aboriginal-Australian Fellowship * Jack Horner (baseball) (1863–1910), American professional ba ...
is currently the major advocate of the idea that ''Tyrannosaurus'' was exclusively a scavenger and did not engage in active hunting at all. Horner has presented several arguments to support the pure scavenger hypothesis. The presence of large
olfactory bulb The olfactory bulb (Latin: ''bulbus olfactorius'') is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OF ...
s and
olfactory nerve The olfactory nerve, also known as the first cranial nerve, cranial nerve I, or simply CN I, is a cranial nerve that contains sensory nerve fibers relating to the sense of smell. The afferent nerve fibers of the olfactory receptor neurons t ...
s suggests a highly developed sense of smell for sniffing out carcasses over great distances. The teeth could crush bone, and therefore could extract as much food (
bone marrow Bone marrow is a semi-solid biological tissue, tissue found within the Spongy bone, spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It i ...
) as possible from carcass remnants, usually the least nutritious parts. At least some of its potential prey could move quickly, while evidence suggests that Tyrannosaurus walked instead of ran. Other evidence suggests hunting behavior in ''Tyrannosaurus''. The eye-sockets of tyrannosaurs are positioned so that the eyes would point forward, giving them
binocular vision Binocular vision is seeing with two eyes. The Field_of_view, field of view that can be surveyed with two eyes is greater than with one eye. To the extent that the visual fields of the two eyes overlap, #Depth, binocular depth can be perceived. Th ...
slightly better than that of modern
hawk Hawks are birds of prey of the family Accipitridae. They are very widely distributed and are found on all continents, except Antarctica. The subfamily Accipitrinae includes goshawks, sparrowhawks, sharp-shinned hawks, and others. This ...
s. Tyrannosaur-inflicted damage has been found on skeletons of hadrosaurs and ''
Triceratops ''Triceratops'' ( ; ) is a genus of Chasmosaurinae, chasmosaurine Ceratopsia, ceratopsian dinosaur that lived during the late Maastrichtian age of the Late Cretaceous Period (geology), period, about 68 to 66 million years ago on the island ...
'' that seemed to have survived initial attacks. Some researchers argue that if ''Tyrannosaurus'' were a scavenger, another dinosaur had to be the top predator in the Amerasian Upper Cretaceous. The top prey were the larger marginocephalians and
ornithopod Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (). They represent one of the most successful groups of herbivorous dinosaurs during the Cretaceous. The most primitive members of the group were bipedal and relatively sm ...
s. The other tyrannosaurids share so many characteristics with ''Tyrannosaurus'' that only small
dromaeosaurs Dromaeosauridae () is a family (biology), family of feathered coelurosaurian Theropoda, theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous period (geology), Period. The name Drom ...
remain as feasible top predators. In this light, scavenger hypothesis adherents have suggested that the size and power of tyrannosaurs allowed them to steal kills from smaller predators.Walters, M., Paker, J. (1995). Dictionary of Prehistoric Life. Claremont Books. . In 2023, a juvenile ''Gorgosaurus'' with its ''
in situ is a Latin phrase meaning 'in place' or 'on site', derived from ' ('in') and ' ( ablative of ''situs'', ). The term typically refers to the examination or occurrence of a process within its original context, without relocation. The term is use ...
'' stomach contents containing two ''
Citipes ''Citipes'' () is an extinct genus of caenagnathid theropod from the Late Cretaceous Dinosaur Park Formation in Alberta, Canada. The genus contains only one species, the type species, ''C. elegans''. The generic name of ''Citipes'' is Latin (l ...
'' juveniles about a year old intact has been reported from the
Dinosaur Park Formation The Dinosaur Park Formation is the uppermost member of the Belly River Group (also known as the Judith River Group), a major geologic unit in southern Alberta. It was deposited during the Campanian stage of the Late Cretaceous, between about 7 ...
. This juvenile would have been 5-7 years old at the time of death, measuring about long and weighing around . It is much larger than the two ''Citipes'' juveniles that weigh about , contrary to the assumption that tyrannosaurids fed on prey of their size once they reached , indicating that juvenile tyrannosaurids still consumed much smaller prey after exceeding a certain size threshold. The discovery of this specimen indicated that tyrannosaurids probably did not hunt in multigenerational packs, since its prey size is too small to share with the conspecifics. It is also a direct dietary evidence that reinforces the theory of 'ontogenetic dietary shift' for tyrannosaurids, as previously inferred by ecological modeling and anatomical features among different age groups. Only the remains of the hindlimbs and caudal vertebrae of juvenile ''Citipes'' were present in the tyrannosaurid's stomach cavity, suggesting that a juvenile ''Gorgosaurus'' may have had preferential consumption of the muscular hindlimbs.


Cannibalism

Evidence also strongly suggests that tyrannosaurids were at least occasionally cannibalistic. ''Tyrannosaurus'' itself has strong evidence pointing towards it having been cannibalistic in at least a scavenging capacity based on tooth marks on the foot bones, humerus, and metatarsals of one specimen. Fossils from the Fruitland Formation,
Kirtland Formation The Kirtland Formation (originally the Kirtland Shale) is a Sedimentary rock, sedimentary geological formation. Description The Kirtland Formation is the product of alluvial muds and overbank sand deposits from the many channels draining the ...
(both Campanian in age), and Maastichtian-aged
Ojo Alamo Formation The Ojo Alamo Formation is a geologic Formation (geology), formation in New Mexico spanning the Mesozoic/Cenozoic boundary. Non-avian dinosaur fossils have controversially been identified in beds of this formation dating from after the Cretaceous ...
suggest that cannibalism was present in various tyrannosaurid genera of the San Juan Basin. The evidence gathered from the specimens suggests opportunistic feeding behavior in tyrannosaurids that cannibalized members of their own species.


Distribution

The earliest known tyranosaur remains occurred between 129.4 and 125 million years ago in Ishikawa, Japan near Lat 36.166668 lng 136.633331. Found b
Marsh in 1881
and identified by H.F. Osborne in 1906, the age of the remains was determined by H. Matsuoka et al. in 2002. While earlier tyrannosauroids are found on all three northern continents, tyrannosaurid fossils are known only from North America and Asia. Sometimes fragmentary remains uncovered in the Southern Hemisphere have been reported as "Southern Hemisphere tyrannosaurids," although these seem to have been misidentified abelisaurid fossils. Tyrannosaurid remains have never been recovered from eastern North America, while more basal tyrannosauroids, like '' Dryptosaurus'' and '' Appalachiosaurus'', persisted there until the end of the Cretaceous, indicating that tyrannosaurids must have evolved in or dispersed into western North America after the continent was divided in half by the
Western Interior Seaway The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, or the Western Interior Sea) was a large inland sea (geology), inland sea that existed roughly over the present-day Great Plains of ...
in the middle of the Cretaceous. Tyrannosaurid fossils have been found in
Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
, which may have provided a route for dispersal between North America and Asia. ''Alioramus'' and ''Tarbosaurus'' are found to be related in one cladistic analysis, forming a unique Asian branch of the family. This was later disproven with the discovery of '' Qianzhousaurus'' and the description of the tyrannosaur family Alioramini. Tyrannosaurid teeth from a large species of unknown variety were discovered in the Nagasaki Peninsula by researchers from the Fukui Prefectural Dinosaur Museum, further expanding the range of the group. The teeth were estimated to be 81 million years old (
Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...
Age). Of the two subfamilies, tyrannosaurines appear to have been more widespread. Albertosaurines are unknown in Asia, which was home to the tyrannosaurines, such as ''Tarbosaurus'' and ''Zhuchengtyrannus'', and ''Qianzhousaurus'' and ''Alioramus'' of the Alioramini. Both the Tyrannosaurinae and Albertosaurinae subfamilies were present in the Campanian and early
Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...
stages of North America, with tyrannosaurines like ''Daspletosaurus'' ranging throughout the Western Interior, while the albertosaurines ''Albertosaurus'' and ''Gorgosaurus'' are currently known only from the northwestern part of the continent. By the late Maastrichtian, albertosaurines appear to have gone extinct, while the tyrannosaurine ''Tyrannosaurus'' roamed from
Saskatchewan Saskatchewan is a Provinces and territories of Canada, province in Western Canada. It is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and to the south by the ...
to
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
. This pattern is mirrored in other North American dinosaur taxa. During the Campanian and early Maastrichtian, lambeosaurine hadrosaurs and centrosaurine
ceratopsia Ceratopsia or Ceratopia ( or ; Ancient Greek, Greek: "horned faces") is a group of herbivore, herbivorous, beaked dinosaurs that thrived in what are now North America, Asia and Europe, during the Cretaceous Period (geology), Period, although ance ...
ns are common in the northwest, while hadrosaurines and
chasmosaurines Chasmosaurinae is a subfamily of Ceratopsidae, ceratopsid dinosaurs. They were one of the most successful groups of herbivores of their time. Chasmosaurines appeared in the early Campanian, and became extinct, along with all other non-bird, avian ...
were more common to the south. By the end of the Cretaceous, centrosaurines are unknown and lambeosaurines are rare, while hadrosaurines and chasmosaurines were common throughout the Western Interior. A study published in the journal ''Scientific Reports'' on February 2, 2016, by Steve Brusatte, Thomas Carr ''et al''. indicates that during the later Maastrichtian, ''Tyrannosaurus'' itself might have been partially responsible for the extinction of the other tyrannosaurids in most of western North America. The study indicates that ''Tyrannosaurus'' might have been an immigrant from Asia as opposed to having evolved in North America (possibly a descendant of the closely related ''Tarbosaurus'') that supplanted and outcompeted other tyrannosaurids. This theory is further supported by the fact that few to no other types of tyrannosaurid are found within ''Tyrannosaurus known range.


Timeline of genera

ImageSize = width:800px height:auto barincrement:15px PlotArea = left:10px bottom:50px top:10px right:10px Period = from:-100.5 till:-60 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:10 start:-100 ScaleMinor = unit:year increment:1 start:-100 TimeAxis = orientation:hor AlignBars = justify Colors = #legends id:CAR value:claret id:ANK value:rgb(0.4,0.3,0.196) id:HER value:teal id:HAD value:green id:OMN value:blue id:black value:black id:white value:white id:latecretaceous value:rgb(0.74,0.82,0.37) BarData= bar:eratop bar:space bar:periodtop bar:space bar:NAM1 bar:NAM2 bar:NAM3 bar:NAM4 bar:NAM5 bar:NAM6 bar:NAM7 bar:NAM8 bar:NAM9 bar:NAM10 bar:NAM11 bar:NAM12 bar:NAM13 bar:NAM14 bar:space bar:period bar:space bar:era PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 shift:(7,-4) bar:periodtop from: -100.5 till: -93.9 color:latecretaceous text:
Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...
from: -93.9 till: -89.8 color:latecretaceous text:
Turonian The Turonian is, in the International Commission on Stratigraphy, ICS' geologic timescale, the second age (geology), age in the Late Cretaceous epoch (geology), Epoch, or a stage (stratigraphy), stage in the Upper Cretaceous series (stratigraphy), ...
from: -89.8 till: -86.3 color:latecretaceous text: Coniac. from: -86.3 till: -83.6 color:latecretaceous text: Sant. from: -83.6 till: -72.1 color:latecretaceous text:
Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...
from: -72.1 till: -66 color:latecretaceous text:
Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...
bar:eratop from: -100.5 till: -66 color:latecretaceous text:
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...
PlotData= align:left fontsize:M mark:(line,white) width:5 anchor:till align:left color:ANK bar:NAM1 from:-80.6 till:-79.9 text: Lythronax color:ANK bar:NAM2 from:-78.5 till:-78.0 text: Dynamoterror color:ANK bar:NAM3 from:-77 till:-76 text:
Teratophoneus ''Teratophoneus'' ("monstrous murderer"; Greek: ''teras'', "monster" and ''phoneus'', "murderer") is a genus of Tyrannosaurinae, tyrannosaurine Theropoda, theropod dinosaur that lived during the late Campanian age of the Late Cretaceous period, ...
color:ANK bar:NAM4 from:-77 till:-74 text: Daspletosaurus color:OMN bar:NAM5 from:-76.6 till:-75.1 text:
Gorgosaurus ''Gorgosaurus'' ( ; ) is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period (Campanian), between about 76.5 and 75 million years ago. Fossil remains have been found in the Ca ...
color:ANK bar:NAM6 from:-74.84 till:-74.26 text:
Bistahieversor ''Bistahieversor'' (meaning "Bistahi destroyer"), also known as the "Bisti Beast", is a genus of basal Eutyrannosauria, eutyrannosaurian Theropoda, theropod dinosaur. The genus contains only a single known species, ''B. sealeyi'', described in 2 ...
color:ANK bar:NAM7 from:-73.6 till:-73.4 text:
Zhuchengtyrannus ''Zhuchengtyrannus'' (meaning "Zhucheng tyrant") is a genus of Tyrannosauridae, tyrannosaurid theropod dinosaur known from the Campanian stage of the Late Cretaceous of Shandong Province, China. It belongs to the subfamily Tyrannosaurinae, and co ...
color:OMN bar:NAM8 from:-71 till:-68 text:
Albertosaurus ''Albertosaurus'' (; meaning "Alberta lizard") is a genus of large tyrannosaurid theropod dinosaur that lived in northwestern North America during the early to middle Maastrichtian age of the Late Cretaceous period, about 71 million yea ...
color:ANK bar:NAM9 from:-70.1 till:-69.9 text: Alioramus color:ANK bar:NAM10 from:-70.1 till:-69.9 text: Tarbosaurus color:ANK bar:NAM11 from:-69.1 till:-69.2 text: Nanuqsaurus color:ANK bar:NAM12 from:-67 till:-66.7 text: Asiatyrannus color:ANK bar:NAM13 from:-67 till:-66 text: Qianzhousaurus color:ANK bar:NAM14 from:-68 till:-66 text:
Tyrannosaurus ''Tyrannosaurus'' () is a genus of large theropod dinosaur. The type species ''Tyrannosaurus rex'' ( meaning 'king' in Latin), often shortened to ''T. rex'' or colloquially t-rex, is one of the best represented theropods. It lived througho ...
PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 bar:period from: -100.5 till: -93.9 color:latecretaceous text:
Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...
from: -93.9 till: -89.8 color:latecretaceous text:
Turonian The Turonian is, in the International Commission on Stratigraphy, ICS' geologic timescale, the second age (geology), age in the Late Cretaceous epoch (geology), Epoch, or a stage (stratigraphy), stage in the Upper Cretaceous series (stratigraphy), ...
from: -89.8 till: -86.3 color:latecretaceous text: Coniac. from: -86.3 till: -83.6 color:latecretaceous text: Sant. from: -83.6 till: -72.1 color:latecretaceous text:
Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...
from: -72.1 till: -66 color:latecretaceous text:
Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...
bar:era from: -100.5 till: -66 color:latecretaceous text:
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...


See also

* Timeline of tyrannosaur research


References


External links


Tyrannosauridae
specimen list and discussion at The Theropod Database {{Authority control Dinosaur families Late Cretaceous dinosaurs