Bistahieversor Temporal range: Late Cretaceous, | |
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Skull and vertebra at the New Mexico Museum of Natural History and Science | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Clade: | † Eutyrannosauria |
Genus: | † Bistahieversor Carr & Williamson, 2010 |
Species: | †B. sealeyi |
Binomial name | |
†Bistahieversor sealeyi Carr & Williamson, 2010 | |
Bistahieversor (meaning "Bistahi destroyer"), 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 [1] 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.
The first remains now attributed to Bistahieversor, a partial skull and skeleton, were described in 1990 as a specimen of Aublysodon . [2] Additional remains, consisting of the incomplete skull and skeleton of a juvenile, were described in 1992. [3] Another complete skull and partial skeleton were found in the Bisti/De-Na-Zin Wilderness Area of New Mexico in 1998, [4] known colloquially as the "Bisti Beast". [5]
In a 2000 paper, Thomas Carr and Thomas Williamson re-examined these four specimens and suggested that they did not belong to Aublysodon, but rather to one or more new species of Daspletosaurus . [6] However, it was not until 2010 that Carr and Williamson published a thorough re-description of the specimens and found that they belonged to a new genus and species of more generalized tyrannosauroid. They named it Bistahieversor sealeyi. [1] The name Bistahieversor comes from the Navajo Bistahí, or "place of the adobe formations" in reference to the Bisti/De-Na-Zin Wilderness Area where it was found. Eversor, the latter part of the name, means "destroyer." [1]
Material from both juveniles and adults has been found in the Kirtland and Fruitland formations of New Mexico. Adult Bistahieversor are estimated to have been around 9 meters (30 ft) long and weigh at least a ton. The snout is deep, indicating that the feature is not unique to more derived tyrannosaurs, such as Tyrannosaurus . Geographical barriers, such as the newly forming Rocky Mountains, may have isolated the more southerly Bistahieversor from more derived northern tyrannosaurs. [7] In 2010, Gregory S. Paul estimated a length of 8 meters (26 ft) and a weight of 2.5 metric tons (2.75 short tons). [8] In 2016, Molina-Pérez and Larramendi gave a length of 9 meters (29.5 ft) and a weight of 3.3 metric tons (3.6 short tons). [9]
Bistahieversor differs from other tyrannosaurs in the possession of 64 teeth, an extra opening above the eye, and a keel along the lower jaw, among many other unique traits. The opening above the eye is thought to have accommodated an air sac that would have lightened the skull's weight. Bistahieversor also had a complex joint at its "forehead" that would have stabilized the skull to prevent movement at the joint. [10]
Bistahieversor is a genus of derived tyrannosaur often classified in the subfamily Tyrannosaurinae. Different datasets have recovered varying placements for it within Eutyrannosauria.
In 2020, Voris et al. recovered Bistahieversor as a basal member of Eutyrannosauria, rather than a tyrannosaurine, diverging later than Dryptosaurus and Appalachiosaurus . These results are displayed in the cladogram below: [11]
Eutyrannosauria |
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In 2024, Rivera-Sylva & Longrich described new remains likely belonging to a novel species of Labocania . Their new data allowed for the reanalysis of Bistahieversor as a member of the tyrannosaurine clade Teratophoneini, in addition to Labocania, Dynamoterror , Teratophoneus , and two unnamed specimens from the Aguja and Two Medicine formations. Their results are displayed in the cladogram below: [12]
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A 2020 study of the endocranial morphology of Bistahieversor shed some light on its hunting behaviors. Its large olfactory bulbs indicate a very heightened sense of smell, while the elongated semi-circular canals implied increased agility and sophisticated gaze stabilization while the head was moving. Bistahieversor also possessed binocular vision, allowing it to see much better than more primitive predatory dinosaurs. The study noted that, while Bistahieversor had small optic lobes, this was not a strong indicator of whether or not this dinosaur possessed poor vision. [13]
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 confidently 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.
Dilong is a genus of small basal tyrannosauroid dinosaurs. The only species in the genus is Dilong paradoxus, known from the Lower Cretaceous Yixian Formation of East Asia. The discovery of Dilong was significant as it provided the first evidence of feathers in tyrannosaurs, something which had previously been suspected for the group.
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.
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.
Albertosaurines, or dinosaurs of the subfamily Albertosaurinae, lived in the Late Cretaceous of United States and Canada. The subfamily was first used by Philip J. Currie, Jørn H. Hurum, and Karol Sabath as a group of tyrannosaurid dinosaurs. It was originally defined as "(Albertosaurus + Gorgosaurus)", including only the two genera. The group is the sister clade to Tyrannosaurinae. In 2007, it was found that the group also contained Maleevosaurus, often synonymized with Tarbosaurus. However, this classification has not been accepted and Maleevosaurus is still considered a juvenile Tarbosaurus or Tyrannosaurus.
Thomas D. Carr is a vertebrate paleontologist who received his PhD from the University of Toronto in 2005. He is now a member of the biology faculty at Carthage College in Kenosha, Wisconsin. Much of his work centers on tyrannosauroid dinosaurs. Carr published the first quantitative analysis of tyrannosaurid ontogeny in 1999, establishing that several previously recognized genera and species of tyrannosaurids were in fact juveniles of other recognized taxa. Carr shared the Lanzendorf Prize for scientific illustration at the 2000 Society of Vertebrate Paleontology conference for the artwork in this article. In 2005, he and two colleagues described and named Appalachiosaurus, a late-surviving basal tyrannosauroid found in Alabama. He is also scientific advisor to the Dinosaur Discovery Museum in Kenosha, Wisconsin.
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.
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.