66-601: Alioramini is a clade of long-snouted tyrannosaurine tyrannosaurids from the Late Cretaceous epoch. It includes the tyrannosaurid genera Alioramus and Qianzhousaurus . Although tyrannosaurids are known from a variety of places around the globe, alioramins are currently restricted to Asia in mostly Maastrichtian strata. Many of the fossils attributed to Alioramini are not from fully developed individuals. Alioramins are medium-sized tyrannosaurids, reaching around 5–7 m (16–23 ft) in length. They have
132-534: A clade (from Ancient Greek κλάδος (kládos) 'branch'), also known as a monophyletic group or natural group , is a grouping of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree . In the taxonomical literature, sometimes the Latin form cladus (plural cladi ) is used rather than the English form. Clades are
198-479: A "ladder", with supposedly more "advanced" organisms at the top. Taxonomists have increasingly worked to make the taxonomic system reflect evolution. When it comes to naming , this principle is not always compatible with the traditional rank-based nomenclature (in which only taxa associated with a rank can be named) because not enough ranks exist to name a long series of nested clades. For these and other reasons, phylogenetic nomenclature has been developed; it
264-509: A Two Medicine bonebed by Currie et al. (2005); the authors stated that this fossil material likely represents then-unnamed species mentioned by Horner et al. (1992), but cautioned that further study and description of Daspletosaurus would be necessary before the species can be determined with certainty. In 2017, the Two Medicine Formation taxon was named as the new species D. horneri . Isolated tyrannosaurid teeth in
330-497: A clade by Junchang Lü and colleagues in 2014, who defined it as a branch-based clade containing all tyrannosaurids more related to Alioramus than to Albertosaurus , Proceratosaurus , and Tyrannosaurus . Hence, the clade Alioramini consists of three species, namely Alioramus altai , Alioramus remotus , and Qianzhousaurus sinensis . Some researchers have tried to synonymize Qianzhousaurus with Alioramus , but many others maintain that they are separate genera. Alioramini
396-623: A clade can be described based on two different reference points, crown age and stem age. The crown age of a clade refers to the age of the most recent common ancestor of all of the species in the clade. The stem age of a clade refers to the time that the ancestral lineage of the clade diverged from its sister clade. A clade's stem age is either the same as or older than its crown age. Ages of clades cannot be directly observed. They are inferred, either from stratigraphy of fossils , or from molecular clock estimates. Viruses , and particularly RNA viruses form clades. These are useful in tracking
462-474: A distinct species yet to be named, referred to as D. sp. In the lower portion of the Judith River Formation, around 78 million years ago, there is some evidence for a new undescribed tyrannosaurid taxon. A specimen in the collections of Triebold Paleontology excavated between 2002 and 2004, known as "Sir William" (RMDRC 2002.MT-001), shows some characteristics of Daspletosaurus suggesting
528-466: A junior synonym of D. torosus . In the same year, however, Warshaw and colleagues supported the validity of this species and referred other specimens to it. While very large by the standard of modern predators, Daspletosaurus was not the largest tyrannosaurid. Adults could reach a length of 8.5–9 metres (28–30 ft) from snout to tail, a hip height of 2.2 metres (7.2 ft), and a body mass of 2–3 metric tons (2.2–3.3 short tons). However there
594-481: A more gracile body plan as compared to most other tyrannosaurines. Alioramins have rather shallow snouts, a trait that is rather rare among tyrannosaurs but can be found in the early tyrannosauroid, Xiongguanlong . Alioramins are unique when compared to contemporary tyrannosaurs from the same time, such as Tarbosaurus and Tyrannosaurus , because most of the longer snouted tyrannosauroids, such as Xiongguanlong, were found in deposits dating to earlier times during
660-424: A new earlier species to the genus. However, the specimen shows many characteristics typical of early tyrannosaurines such as Teratophoneus and even some of the later Tyrannosaurus , which may suggest an entirely new genus. In 2017, John Wilson discovered the bones of a tyrannosaurid, including a partial disarticulated skull, cervical, sacral, and caudal vertebrae, and a rib, chevron, and first metatarsal, from
726-422: A revised taxonomy based on a concept strongly resembling clades, although the term clade itself would not be coined until 1957 by his grandson, Julian Huxley . German biologist Emil Hans Willi Hennig (1913–1976) is considered to be the founder of cladistics . He proposed a classification system that represented repeated branchings of the family tree, as opposed to the previous systems, which put organisms on
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#1732791287843792-416: A short, S-shaped neck supporting the massive skull. It walked on its two thick hindlimbs, which ended in four-toed feet, although the first digit (the hallux ) did not contact the ground. In contrast, the forelimbs were extremely small and bore only two digits , although Daspletosaurus had the longest forelimbs in proportion to body size of any tyrannosaurid. A long, heavy tail served as a counterweight to
858-534: A species of Daspletosaurus , D. degrootorum , but this has not been widely supported. Daspletosaurus is closely related to the much larger and more recent tyrannosaurid Tyrannosaurus rex . Like most tyrannosaurids, Daspletosaurus was a large bipedal predator , with the average adult measuring 8.5–9 m (28–30 ft) and weighing 3 metric tons (3.3 short tons). However, the largest potential specimen measures around 11 metres (36 ft) long and weighs up to 5 metric tons (5.5 short tons). Daspletosaurus had
924-429: A suffix added should be e.g. "dracohortian". A clade is by definition monophyletic , meaning that it contains one ancestor which can be an organism, a population, or a species and all its descendants. The ancestor can be known or unknown; any and all members of a clade can be extant or extinct. The science that tries to reconstruct phylogenetic trees and thus discover clades is called phylogenetics or cladistics ,
990-1030: Is a genus of tyrannosaurid dinosaur that lived in Laramidia between about 78 and 74.4 million years ago, during the Late Cretaceous Period . The genus Daspletosaurus contains three named species . Fossils of the earlier type species , D. torosus , have been found in Alberta , while fossils of a later species, D. horneri , have been found only in Montana . D. wilsoni has been suggested as an intermediate species between D. torosus and D. horneri that evolved through anagenesis , but this theory has been disputed by other researchers. There are also multiple specimens which may represent new species of Daspletosaurus from Alberta and Montana, but these have not been formally described. The taxon Thanatotheristes has been suggested to represent
1056-851: Is a cladogram of Tyrannosaurinae based on the phylogenetic analysis conducted by Warshaw & Fowler (2022). Here, it is proposed that the three Daspletosaurus species evolved through anagenesis in the Tyrannosaurinae in a line leading to Zhuchengtyrannus , Tarbosaurus , and Tyrannosaurus . Due to their more fragmentary nature, Thanatotheristes and Nanuqsaurus were excluded from this analysis. Alioramus remotus [REDACTED] Alioramus altai [REDACTED] Qianzhousaurus [REDACTED] Dynamoterror Teratophoneus [REDACTED] Lythronax [REDACTED] Daspletosaurus wilsoni Daspletosaurus horneri Zhuchengtyrannus Tarbosaurus [REDACTED] In 2024, Scherer and Voiculescu-Holvad argued that
1122-499: Is also used with a similar meaning in other fields besides biology, such as historical linguistics ; see Cladistics § In disciplines other than biology . The term "clade" was coined in 1957 by the biologist Julian Huxley to refer to the result of cladogenesis , the evolutionary splitting of a parent species into two distinct species, a concept Huxley borrowed from Bernhard Rensch . Many commonly named groups – rodents and insects , for example – are clades because, in each case,
1188-476: Is in turn included in the mammal, vertebrate and animal clades. The idea of a clade did not exist in pre- Darwinian Linnaean taxonomy , which was based by necessity only on internal or external morphological similarities between organisms. Many of the better known animal groups in Linnaeus's original Systema Naturae (mostly vertebrate groups) do represent clades. The phenomenon of convergent evolution
1254-671: Is no stratigraphic overlap between D. torosus and D. wilsoni , since a large specimen (CMC VP 15826) previously referred to as D. torosus is from a strata recently dated to be later than D. wilsoni , and since this specimen likely belongs to a distinct species of Daspletosaurus yet to be named. They also recovered the paraphyletic Daspletosaurus at the base of Tyrannosaurini, making the genus ancestral to Tyrannosaurus . There are indications of D. horneri possessing integumentary sensory organs, possibly used in touch, modulation of precise jaw movements, temperature reading, and prey detection. The large flat scales may have further protected
1320-418: Is one potential specimen of D. torosus or a new unnamed species, CMC VP 15826 (nicknamed "Pete III"), that suggests the genus could reach lengths of nearly 11 metres (36 ft) and weigh 5 metric tons (5.5 short tons). Daspletosaurus had a massive skull that could reach more than 1 metre (3 ft 3 in) in length. The bones were heavily constructed and some, including the nasal bones on top of
1386-515: Is responsible for many cases of misleading similarities in the morphology of groups that evolved from different lineages. With the increasing realization in the first half of the 19th century that species had changed and split through the ages, classification increasingly came to be seen as branches on the evolutionary tree of life . The publication of Darwin's theory of evolution in 1859 gave this view increasing weight. In 1876 Thomas Henry Huxley , an early advocate of evolutionary theory, proposed
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#17327912878431452-405: Is some evidence of niche differentiation between the two. While Daspletosaurus fossils are not as common as other tyrannosaurid fossils, the available specimens allow some analysis of the biology of these animals, including social behavior , diet, and life history. The type specimen of Daspletosaurus torosus ( CMN 8506) is a partial skeleton including the skull, the shoulder, a forelimb,
1518-489: Is still controversial. As an example, see the full current classification of Anas platyrhynchos (the mallard duck) with 40 clades from Eukaryota down by following this Wikispecies link and clicking on "Expand". The name of a clade is conventionally a plural, where the singular refers to each member individually. A unique exception is the reptile clade Dracohors , which was made by haplology from Latin "draco" and "cohors", i.e. "the dragon cohort "; its form with
1584-485: Is usually considered to be a part of the Tyrannosaurinae subfamily within the Tyrannosauridae family; however, some phylogenetic studies find them to be outside the Tyrannosauridae. Alioramini is a part of Tyrannosaurinae, based on several features. These features include a maxillary process of the premaxilla that points upwards; the deep joint surface in the maxilla conceals certain features related to tooth roots;
1650-698: The Dinosaur Park Formation in Alberta. The Dinosaur Park Formation was formerly known as the Upper Oldman Formation and dates back to the middle Campanian, between 76.5 and 74.8 million years ago . Daspletosaurus fossils are known specifically from the middle to upper section of the formation, between 75.6 and 75.0 million years ago. In 1914, Brown collected a nearly complete skeleton and skull; forty years later his American Museum of Natural History sold this specimen to
1716-569: The Field Museum of Natural History in Chicago . It was mounted for display in Chicago and labeled as Albertosaurus libratus for many years, but after several skull features were later found to be modeled in plaster, including most of the teeth, the specimen ( FMNH PR308) was reassigned to Daspletosaurus torosus by Thomas Carr in 1999. A total of eight specimens have been collected from
1782-490: The Greek δασπλής ( dasplēs , stem and connective vowel resulting in dasplēto -) ("frightful") and σαυρος ( sauros ) ("lizard"). The type species is Daspletosaurus torosus , the specific name torosus being Latin for 'muscular' or 'brawny'. Aside from the type, there is only one other well-known specimen, RTMP 2001.36.1, a relatively complete skeleton discovered in 2001. Both specimens were recovered from
1848-581: The Oldman Formation in the Judith River Group of Alberta. The Oldman Formation was deposited during the middle Campanian stage of the Late Cretaceous , from about 79.5 to 77 Ma (million years ago). Dale Russell also suggested that a specimen of an immature Albertosaurus (CMN 11315) from the younger Horseshoe Canyon Formation in Alberta actually belonged to a third specimen of Daspletosaurus as D. cf. torosus , extending
1914-546: The dentary bone, alioramins have 18 or more teeth. The name Alioramini was first coined in 1995 by George Olshevsky only to contain the at-the-time uncertain Alioramus . Olshevsky classified Alioramini within the base of Tyrannosaurinae and considered it to be a tribe or a "paratribe" (a name for a paraphyletic tribe, emphasizing Olshevsky's view that the hypothetical common ancestor of tyrannosaurids could be classified as an alioramin). Alioramini were first described as
1980-400: The pelvis , a femur, and all of the vertebrae from the neck, torso, and hip, as well as the first eleven tail vertebrae. It was discovered in 1921 near Steveville, Alberta , by Charles Mortram Sternberg , who thought it was a new species of Gorgosaurus . It was not until 1970 that the specimen was fully described by Dale Russell , who made it the type of a new genus, Daspletosaurus , from
2046-420: The "Jack’s B2" site of the Judith River Formation. Elías A. Warshaw and Denver W. Fowler described these remains ( BDM 107) in 2022 as belonging to a new species of Daspletosaurus , D. wilsoni . It represents a transitional species between D. torosus and D. horneri , as it existed between them in time. It has been suggested that the three species may have evolved directly through anagenesis , but this theory
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2112-469: The Cretaceous. Members of the alioramins also have an elongated maxillary fenestra. Besides their elongated snouts, perhaps another major trait that makes alioramins stand out is their nasal ridges. While most other tyrannosaurids have nasal ridges, the nasal ridges in alioramins are pronounced and discrete. They form well developed bumps on the surface of the nasal bones, forming their nasal crest. Within
2178-557: The Dinosaur Park Formation over the years since, most of them within the boundaries of Dinosaur Provincial Park . Phil Currie believes that the Dinosaur Park specimens represent a new species of Daspletosaurus , distinguished by certain features of the skull. Pictures of this new species have been published, but it still awaits a name and full description in print. In 2024, Warshaw and colleagues suggested that
2244-471: The Dinosaur Park specimens likely belong to D. wilsoni . A new tyrannosaurid specimen ( OMNH 10131), including skull fragments, ribs, and parts of the hindlimb, was reported from New Mexico in 1990 and assigned to the now-defunct genus Aublysodon . Many later authors have reassigned this specimen, along with a few others from New Mexico, to yet another unnamed species of Daspletosaurus . However, research published in 2010 showed that this species, from
2310-682: The Hunter Wash Member of the Kirtland Formation , is actually a more primitive tyrannosauroid, and was classified in the genus Bistahieversor . In 1992, Jack Horner and colleagues published an extremely preliminary report of a tyrannosaurid from the upper parts of the Campanian Two Medicine Formation in Montana, which was interpreted as a transitional species between Daspletosaurus and
2376-399: The animal survived the bite. 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
2442-683: The basis of morphological and stratigraphical data, and that anagenesis will not be supported unequivocally due to the limited sample and nature of the fossil record, which does not show a great degree of variation in morphology. The cladogram presented for their phylogenetic analysis is shown below. Alioramus remotus [REDACTED] Alioramus altai Qianzhousaurus [REDACTED] Lythronax [REDACTED] Teratophoneus Dynamoterror Thanatotheristes Daspletosaurus horneri Daspletosaurus wilsoni Dinosaur Park and Oldman formations taxon ( TMP 2001.36.1) Zhuchengtyrannus Tarbosaurus [REDACTED] In
2508-496: The bites are due to intraspecific competition for territory or resources, or for dominance within a social group. A young specimen of the tyrannosaurid (TMP 1994.143.1), initially identified as the Dinosaur Park Daspletosaurus but subsequently referred to Gorgosaurus libratus , also shows bite marks on the face that were inflicted by another tyrannosaur. The bite marks are healed over, indicating that
2574-665: The characteristic elongated snout morphology of alioramins was likely maintained throughout their ontogeny (growth). Studies on the morphology of tyrannosauroid skulls published in August, 2024 suggest that alioramins experienced lower amounts of stress in their skulls when biting and feeding. The same study indicates that these theropods likely did not utilize puncture-and-pull feeding like larger tyrannosaur genera such as Tyrannosaurus and Daspletosaurus. [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Clade In biological phylogenetics ,
2640-482: The diagnostic skeletal traits used to identify mature tyrannosaurids. An additional maxilla and various teeth from an Edmontosaurus -dominated bonebed in the Horseshoe Canyon Formation was also mistakenly referred to Daspletosaurus , but all the tyrannosaurid material has all since been confirmed to belong to Albertosaurus . Over the years, various additional species have been assigned to
2706-609: 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 , where non-cooperative individuals mob carcasses, frequently attacking and even cannibalizing each other in the process. Fossils of other tyrannosaurids like Teratophoneus and Albertosaurus among other genera suggest that gregarious behavior may have been widespread in tyrannosaurs and thus may vindicate
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2772-451: The fundamental unit of cladistics , a modern approach to taxonomy adopted by most biological fields. The common ancestor may be an individual, a population , or a species ( extinct or extant ). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups. Over
2838-412: The genus Daspletosaurus . Though some have been designated as Daspletosaurus spp, this does not imply that they all represent the same species. Along with the holotype , Russell designated a specimen collected by Barnum Brown in 1913 as the paratype of D. torosus . This specimen ( AMNH 5438) consists of parts of the hindleg, the pelvis, and some of its associated vertebrae. It was discovered in
2904-546: The group consists of a common ancestor with all its descendant branches. Rodents, for example, are a branch of mammals that split off after the end of the period when the clade Dinosauria stopped being the dominant terrestrial vertebrates 66 million years ago. The original population and all its descendants are a clade. The rodent clade corresponds to the order Rodentia, and insects to the class Insecta. These clades include smaller clades, such as chipmunk or ant , each of which consists of even smaller clades. The clade "rodent"
2970-577: The head and torso, with the center of gravity over the hips. From a comparison of the degree of wear of teeth of Daspletosaurus with other extinct and extant animals, it is concluded that Daspletosaurus , as well as other non-avian theropods, had lips that protected the teeth from external influences. Due to this feature, the snout of Daspletosaurus more closely resembled lizards than crocodiles, which lack lips. A skin impression from Daspletosaurus torosus has been described, showing small polygonal scales measuring 3 mm in diameter. The placement of
3036-590: The last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic . Some of the relationships between organisms that the molecular biology arm of cladistics has revealed include that fungi are closer relatives to animals than they are to plants, archaea are now considered different from bacteria , and multicellular organisms may have evolved from archaea. The term "clade"
3102-574: The later Tyrannosaurus . Currie (2003) stated that the tyrannosaurid from the Two Medicine Formation mentioned by Horner et al. (1992) may be an unnamed third species of Daspletosaurus . Another partial skeleton was reported from the Upper Two Medicine in 2001, preserving the remains of a juvenile hadrosaur in its abdominal cavity . This specimen was assigned to Daspletosaurus but not to any particular species. The remains of at least three more Daspletosaurus have also been described in
3168-518: The latter term coined by Ernst Mayr (1965), derived from "clade". The results of phylogenetic/cladistic analyses are tree-shaped diagrams called cladograms ; they, and all their branches, are phylogenetic hypotheses. Three methods of defining clades are featured in phylogenetic nomenclature : node-, stem-, and apomorphy-based (see Phylogenetic nomenclature§Phylogenetic definitions of clade names for detailed definitions). The relationship between clades can be described in several ways: The age of
3234-539: The most basal species, in spite of being the youngest species stratigraphically. While the authors did not completely refute the possibility that anagenesis was the main driver of Daspletosaurus evolution based on the intermediate morphological features, they also suggested that D. wilsoni may be a junior synonym of D. torosus , since there is a near lack of autapomorphic characters that can differentiate this species. They also claimed that Daspletosaurus did not evolve from Thanatotheristes , since they found no support on
3300-608: The other subfamily, the Albertosaurinae. It further belongs to the tribe Daspletosaurini, consisting of it and the taxon Thanatotheristes . Daspletosaurus is usually considered to be closely related to Tyrannosaurus rex , or even a direct ancestor through anagenesis . Gregory Paul reassigned D. torosus to the genus Tyrannosaurus , creating the new combination Tyrannosaurus torosus , but this has not been generally accepted. Many researchers believe Tarbosaurus and Tyrannosaurus to be sister taxa or even to be
3366-404: The particular shape of the lacrimal, mostly hidden from view; and an ectopterygoid with a pneumatic recess that possesses a distinctive round or triangular shape. Dryptosaurus , usually placed as a basal eutyrannosaur is found to be a member of Alioramini under a Bayesian analysis in 2016 Carr and Brusatte paper, but this is the only time in the 2016 paper an analysis yields such a result with
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#17327912878433432-887: The relationships of Alioramini by Loewen et al. (2013) places Alioramini outside of the Tyrannosauridae. Proceratosaurus bradleyi Kileskus aristotocus Guanlong wucaii Sinotyrannus kazuoensis Juratyrant langhami Stokesosaurus clevelandi Dilong paradoxus Eotyrannus lengi Bagaraatan ostromi Raptorex kriegsteini Dryptosaurus aquilunguis Alectrosaurus olseni Xiongguanlong baimoensis Appalachiosaurus montgomeriensis Alioramus altai Alioramus remotus Tyrannosauridae Alioramins, due to their relatively gracile build and long snouts, were likely specialized in hunting small-sized prey with quick turns. Such feeding strategies may have avoided direct competition with other tyrannosaurids. In contrast to robust tyrannosaurids, whose juveniles underwent drastic changes in their skull,
3498-477: 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 numerous 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 , although this cannot be stated with certainty. Other scientists are skeptical of
3564-575: The rest of the paper placing Dryptosaurus in its usual position. Below is a cladogram showing the placement of Alioramini within the Tyrannosaurinae, according to Brusatte & Carr (2016). Gorgosaurus libratus Albertosaurus sarcophagus Qianzhousaurus sinensis Alioramus altai Alioramus remotus Nanuqsaurus hoglundi Teratophoneus curriei Lythronax argestes Daspletosaurus horneri Daspletosaurus torosus Zhuchengtyrannus magnus Tarbosaurus bataar Tyrannosaurus rex Another cladogram showing
3630-504: The rough outer surface of the maxilla (upper jaw bone) and the pronounced crests around the eyes on the lacrimal , postorbital , and jugal bones. The orbit (eye socket) was a tall oval, somewhere in between the circular shape seen in Gorgosaurus and the 'keyhole' shape of Tyrannosaurus . Split carinae (edges) have been found on Daspletosaurus teeth. Daspletosaurus shared the same body form as other tyrannosaurids, with
3696-489: The same genus, with Daspletosaurus a more basal relative. On the other hand, Phil Currie and colleagues find Daspletosaurus to be more closely related to Tarbosaurus and other Asian tyrannosaurids like Alioramus than to the North American Tyrannosaurus . The systematics ( evolutionary relationships) of Daspletosaurus have become clearer as new species have been described. Below
3762-461: The same year, Warshaw and colleagues supported the anagenesis theory by referring other specimens to D. wilsoni (including the Dinosaur Park specimen) which they considered as a valid taxon, and by reanalysing the previous study of Scherer and Voiculescu-Holvad (2024). They claimed that the known species of Daspletosaurus show a gradient of morphologies consistent with them representing a series of ancestors and descendants. They also argued that there
3828-442: The scales on the body is not known. Daspletosaurus belongs in the subfamily Tyrannosaurinae within the family Tyrannosauridae , along with Tarbosaurus , Tyrannosaurus , and Alioramini . Animals in this subfamily are more closely related to Tyrannosaurus than to Albertosaurus and are known – with the exception of Alioramus – for their robust build with proportionally larger skulls and longer femora than in
3894-445: The small forelimbs typical of tyrannosaurids, although they were proportionately longer than in other genera. As an apex predator equipped with dozens of large, sharp teeth, Daspletosaurus was at the top of the food chain , probably preying on large dinosaurs like the ceratopsid Centrosaurus and the hadrosaur Hypacrosaurus . In some areas, Daspletosaurus coexisted with another tyrannosaurid, Gorgosaurus , though there
3960-532: The snout during prey capture and intra-specific combat. A full-grown Dinosaur Park Daspletosaurus ( TMP 85.62.1) exhibits tyrannosaur bite marks on its skull. While it is possible that the bites were attributable to other species, intraspecific aggression such as 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 . Darren Tanke and Phil Currie hypothesize that
4026-430: The snout, were fused for strength. Large fenestrae (openings) in the skull reduced its weight. An adult Daspletosaurus was armed with about six dozen teeth that were very long but oval in cross section rather than blade-like. Unlike its other teeth, those in the premaxilla at the end of the upper jaw had a D-shaped cross section, an example of heterodonty always seen in tyrannosaurids. Unique skull features included
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#17327912878434092-530: The spread of viral infections . HIV , for example, has clades called subtypes, which vary in geographical prevalence. HIV subtype (clade) B, for example is predominant in Europe, the Americas and Japan, whereas subtype A is more common in east Africa. Daspletosaurus torosus Daspletosaurus ( / d æ s ˌ p l iː t ə ˈ s ɔːr ə s / das- PLEET -ə- SOR -əs ; meaning "frightful lizard")
4158-408: The stratigraphic ranges of D. torosus , D. wilsoni and an unnamed species from the Dinosaur Park Formation and Oldman Formation show a clear overlap, indicating that anagenesis may not be the predominant factor of speciation within the genus, since all species of Daspletosaurus were contemporaneous with each other at some point during its evolution. Phylogenetic analyzes resolved D. horneri as
4224-499: The temporal range of the genus by approximately 3.5 million years into the Maastrichtian . He based this referral on features of its limb and pelvic girdle, as well as the curvature of the hand claws, which he interpreted as traits matching Daspletosaurus . This reassignment was not universally accepted, and thorough re-examination of the specimen favored its initial referral to Albertosaurus sarcophagus , despite lacking many of
4290-564: The upper portions of the Judith River Formation are likely from Gorgosaurus as well as some species of Daspletosaurus , probably D. torosus . In 2009, preliminary preparation of a Daspletosaurus specimen from the Coal Ridge Member of the Judith River Formation measuring about 11 metres (36 ft) long was reported. Some researchers assigned this specimen to D. torosus , while others considered it to be
4356-639: Was disputed by Scherer and Voiculescu-Holvad in 2024. However, at the 2023 meeting of the Society of Vertebrate Paleontology , Thomas Carr and Stephen Brusatte presented evidence questioning the validity of D. wilsoni. They said the autapomorphy (unique feature) of D. wilsoni was incorrectly determined, rendering the species a nomen dubium , but they found BDM 107 actually shared traits with D. torosus but not with D. horneri, prompting them to synonymize D. wilsoni with D. torosus . In 2024, Scherer and Voiculescu-Holvad also suggested that D. wilsoni may be
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