Daspletosaurins Temporal range: Late Cretaceous, middle Campanian | |
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Skeletal mount of Daspletosaurus torosus | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Family: | † Tyrannosauridae |
Subfamily: | † Tyrannosaurinae |
Clade: | † Daspletosaurini Voris et al., 2020 |
Type species | |
Daspletosaurus torosus Russell, 1970 | |
Genera | |
Daspletosaurini is an extinct clade of tyrannosaurine dinosaurs that lived in Laramidia during the Late Cretaceous (Middle Campanian) period. It consists of two genera: Daspletosaurus and Thanatotheristes . Four species have been described in the two genera, namely Daspletosaurus torosus, Daspletosaurus horneri, Daspletosaurus wilsoni, and Thanatotheristes degrootorum. At one point all of them were assigned as specimens of D. torosus, but several papers since 2017 have found them to represent distinct species. Some researchers found anagenesis in the group, whether contained in a daspletosaurin clade or paraphyletic in respect to the lineage of tyrannosaurines leading up to Tyrannosaurus , [1] [2] [3] but a 2023 study refuted this theory on the basis of morphological and stratigraphical data. [4]
Daspletosaurins were large predators, reaching around 9 metres (30 ft) in length. [1] However, they were not the largest tyrannosaurids, as more derived taxa, such as Tyrannosaurus , could reach lengths of more than 12 metres (39 ft). [5]
Daspletosaurini is diagnosed by characteristics such as the presence of an extremely coarse subcutaneous surface of the maxilla anteroventral to the antorbital fossa; a constricted jugal ramus of maxilla; the anteroventral corner of the maxilla tapers into a shallow angle (<65°) as measured between the alveolar margin of the first two alveoli and the anterior margin of the subcutaneous surface; a prefrontal that is broad in dorsal view and strongly dorsomedially arced in anterior view; a dentary chin located ventral to either the third alveolus or third interdental plate and possessing no fewer than 14 maxillary teeth. [2]
In the 2020 description of Thanatotheristes , Voris et al. erected Daspletosaurini as a new clade within Tyrannosauridae, as a sister taxon to a clade comprising Zhuchengtyrannus , Tarbosaurus , and Tyrannosaurus . The cladogram below shows the results of the phylogenetic analyses performed by Voris et al. (2020): [2]
Tyrannosauridae |
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In 2022, Warshaw & Fowler 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. The cladogram below shows the results of the phylogenetic analysis performed by Warshaw & Fowler (2022). [3]
Tyrannosaurinae |
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In 2023, Scherer and Voiculescu-Holvad argued that 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 analyses resolved D. horneri as the most basal species, in spite of the fact that it's stratigraphically the youngest. 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 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 doesn't show a great degree of variation in morphology. The cladogram presented for their phylogenetic analysis is shown below. [4]
Tyrannosaurinae |
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Tyrannosauridae is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to fifteen genera, including the eponymous Tyrannosaurus. The exact number of genera is controversial, with some experts recognizing as few as three. All of these animals lived near the end of the Cretaceous Period and their fossils have been found only in North America and Asia.
Tarbosaurus is a genus of large tyrannosaurid dinosaur that lived in Asia during the Late Cretaceous epoch, about 70 million years ago. It contains the single type species: Tarbosaurus bataar, which is known from the Nemegt Formation of Mongolia, with more fragmentary remains found further afield in the Subashi Formation of China. Tarbosaurus is represented by dozens of fossil specimens, including several complete skulls and skeletons. These remains have allowed studies focusing on its phylogeny, skull mechanics, and brain structure. Further fossil remains have been reported from other geologic formations of Asia, however, these remains are fragmentary and can not be confidentially assigned to Tarbosaurus or the type species.
Daspletosaurus 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.
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 Canadian province of Alberta and the U.S. state of Montana. Paleontologists recognize only the type species, G. libratus, although other species have been erroneously referred to the genus.
Aublysodon is a 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. The only currently recognized species, Aublysodon mirandus, was named by paleontologist Joseph Leidy in 1868. It is sometimes considered dubious now, because the type specimen consists only of an isolated premaxillary (front) tooth. Although this specimen is now lost, similar teeth have been found in many US states, western Canada, and Asia. These teeth almost certainly belong to juvenile tyrannosaurine tyrannosaurids, but most have not been identified to species level. However, it is likely that the type tooth belongs to one of the species in the genus Daspletosaurus, which was present in contemporary formations, and which matches specific details of the original tooth. The synapomorphies alleged to distinguish the Aublysodontinae, especially lack of serrations on premaxillary teeth could have been caused by tooth wear in life, postmortem abrasion, or digestion. Most other "aublysodontine"-type teeth may be from ontogenetic stages or sexual morphs of other tyrannosaurids.
Appalachiosaurus is a genus of tyrannosaurian theropod dinosaur from the Late Cretaceous period of what is now eastern North America. It was a basal member of the Eutyrannosauria clade meaning it was rather close in relation to the true tyrannosaurids such as Tyrannosaurus. Like most theropods, it was a bipedal predator. Only a juvenile skeleton has been found, representing an animal approximately 6.5 metres (21 ft) long and weighing 623 kilograms (1,373 lb), which indicates an adult would have been significantly larger.
Alioramus is a genus of tyrannosaurid theropod dinosaurs from the Late Cretaceous period of Asia. It currently contains two species. The type species, A. remotus is known from a partial skull and three foot bones recovered from the Mongolian Nemegt Formation, which was deposited in a humid floodplain about 70 million years ago. These remains were named and described by Soviet paleontologist Sergei Kurzanov in 1976. A second species, A. altai, known from a much more complete skeleton also from the Nemegt Formation, was named and described by Stephen L. Brusatte and colleagues in 2009. Its relationships to other tyrannosaurid genera were at first unclear, with some evidence supporting a hypothesis that Alioramus was closely related to the contemporary species Tarbosaurus bataar. However, the discovery of Qianzhousaurus indicates that it belongs to a distinct branch of tyrannosaurs, namely the tribe Alioramini.
Labocania is a genus of carnivorous theropod dinosaur of disputed affinities from the Late Cretaceous of Mexico. Initially regarded as an indeterminate theropod, later studies mentioned possible affinities with tyrannosaurids, abelisaurids, or carcharodontosaurids. More recent research based on additional fossil material found support for a position within the tyrannosaurine clade Teratophoneini. Two species have been proposed: L. anomala, likely from the La Bocana Roja Formation, and L. aguillonae from the Cerro del Pueblo Formation.
Tyrannosauroidea is a superfamily of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period. By the end of the Cretaceous Period, tyrannosauroids were the dominant large predators in the Northern Hemisphere, culminating in the gigantic Tyrannosaurus. Fossils of tyrannosauroids have been recovered on what are now the continents of North America, Europe and Asia, with fragmentary remains possibly attributable to tyrannosaurs also known from South America and Australia.
The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group. It dates to the Late Cretaceous, between 79 and 75.3 million years ago, corresponding to the "Judithian" land vertebrate age. It was laid down during the same time period as portions of the Two Medicine Formation of Montana and the Oldman Formation of Alberta. It is an historically important formation, explored by early American paleontologists such as Edward Drinker Cope, who named several dinosaurs from scrappy remains found here on his 1876 expedition. Modern work has found nearly complete skeletons of the hadrosaurid Brachylophosaurus.
Tyrannosaurinae is one of the two extinct subfamilies of Tyrannosauridae, a family of coelurosaurian theropods that consists of at least three tribes and several genera. All fossils of these genera have been found in the Late Cretaceous deposits of western North America and east Asia. Compared to the related subfamily Albertosaurinae, tyrannosaurines overall are more robust and larger though the alioramins were gracile by comparison. This subfamily also includes Lythronax, one of the oldest known tyrannosaurid genera, as well as the youngest and most famous member of the group, Tyrannosaurus rex.
Bistahieversor, also known as the "Bisti Beast", is a genus of basal eutyrannosaurian theropod dinosaur. The genus contains only a single known species, B. sealeyi, described in 2010, from the Late Cretaceous of New Mexico. The holotype and a juvenile were found in the Hunter Wash Member of the Kirtland Formation, while other specimens came from the underlying Fossil Forest member of the Fruitland Formation. This dates Bistahieversor approximately 75.5 to 74.5 million years ago during the Campanian age, found in sediments spanning a million years.
Teratophoneus is a genus of tyrannosaurine theropod dinosaur that lived during the late Campanian age of the Late Cretaceous period, in what is now Utah. It contains a single known species, T. curriei. It is known from an incomplete skull and postcranial skeleton recovered from the Kaiparowits Formation and was specifically named T. curriei in honor of famed paleontologist Philip J. Currie.
Zhuchengtyrannus is a genus of tyrannosaurid theropod dinosaur known from the Campanian stage of the Late Cretaceous of Shandong Province, China. It belongs to the subfamily Tyrannosaurinae, and contains a single species, Zhuchengtyrannus magnus.
Lythronax is a genus of tyrannosaurid dinosaur that lived in North America around 81.9-81.5 million years ago during the Late Cretaceous period. The only known specimen was discovered in Utah in the Wahweap Formation of the Grand Staircase–Escalante National Monument in 2009, and it consists of a partial skull and skeleton. In 2013, it became the basis of the new genus and species Lythronax argestes; the generic name Lythronax means "gore king", and the specific name argestes originates from the Greek poet Homer's name for the wind from the southwest, in reference to the specimen's geographic provenance in North America.
Nanuqsaurus is a genus of tyrannosaurine theropod dinosaur known from the Late Cretaceous period Prince Creek Formation of the North Slope of Alaska, having lived roughly 70-68 million years ago. It contains a single species, Nanuqsaurus hoglundi, known only from a partial skull and multiple undescribed postcranial and teeth elements.
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.
This timeline of tyrannosaur research is a chronological listing of events in the history of paleontology focused on the tyrannosaurs, a group of predatory theropod dinosaurs that began as small, long-armed bird-like creatures with elaborate cranial ornamentation but achieved apex predator status during the Late Cretaceous as their arms shrank and body size expanded. Although formally trained scientists did not begin to study tyrannosaur fossils until the mid-19th century, these remains may have been discovered by Native Americans and interpreted through a mythological lens. The Montana Crow tradition about thunder birds with two claws on their feet may have been inspired by isolated tyrannosaurid forelimbs found locally. Other legends possibly inspired by tyrannosaur remains include Cheyenne stories about a mythical creature called the Ahke, and Delaware stories about smoking the bones of ancient monsters to have wishes granted.
Dynamoterror is a monospecific genus of tyrannosaurid dinosaur from New Mexico that lived during the Late Cretaceous in what is now the upper Allison Member of the Menefee Formation. The type and only species, Dynamoterror dynastes, is known from a subadult or adult individual about 9 metres long with an incomplete associated skeleton. It was named in 2018 by Andrew T. McDonald, Douglas G. Wolfe and Alton C. Dooley, Jr. Dynamoterror was closely related to Teratophoneus and Lythronax.
Thanatotheristes is a genus of tyrannosaurid dinosaur from the Late Cretaceous of Laramidia, approximately 80.1-79.5 Ma. Thanatotheristes contains only one species, T. degrootorum. Fossils of this taxon are found in the Foremost Formation of Alberta, Canada, coexisting with medium-sized ceratopsids like Xenoceratops foremostensis and small pachycephalosaurids like Colepiocephale lambei.