Bistahieversor
Encyclopedia
Bistahieversor is a genus
of tyrannosauroid dinosaur
. Bistahieversor existed around 75 million years ago during the Late Cretaceous
.
The name Bistahieversor comes from the Navajo
, or "place of the adobe formations" in reference to the Bisti/De-Na-Zin Wilderness
where it was found, and eversor, meaning "destroyer."
of New Mexico
. Adult Bistahieversor are estimated to have been around 9 metres (29.5 ft) long, weighing 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.
Bistahieversor differs from other tyrannosaurs in the possession of 64 teeth, an extra opening above the eye, and a keel along the lower jaw. 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, preventing movement at the joint.
. Additional remains, consisting of the incomplete skull and skeleton of a juvenile, were described in 1992. Another, complete, skull and partial skeleton were found in the Bisti/De-Na-Zin Wilderness
of New Mexico
in 1998. 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
. 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, which they named Bistahieversor sealeyi.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of tyrannosauroid dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
. Bistahieversor existed around 75 million years ago during the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
.
The name Bistahieversor comes from the Navajo
Navajo language
Navajo or Navaho is an Athabaskan language spoken in the southwestern United States. It is geographically and linguistically one of the Southern Athabaskan languages .Navajo has more speakers than any other Native American language north of the...
, or "place of the adobe formations" in reference to the Bisti/De-Na-Zin Wilderness
Bisti/De-Na-Zin Wilderness
The Bisti/De-Na-Zin Wilderness is a wilderness area located in San Juan County in the U.S. state of New Mexico. Established in 1984, the Wilderness is a desolate area of steeply eroded badlands managed by the Bureau of Land Management, with the exception of three parcels of private Navajo land...
where it was found, and eversor, meaning "destroyer."
Description
Material from both adolescent and adult individuals has been found in the Kirtland FormationKirtland Formation
The Kirtland Formation is a sedimentary geological formation. It is the product of alluvial muds and overbank sand deposits from the many channels draining the coastal plain that existed on the inland seashore of North America, in the late Cretaceous period. It overlies the Fruitland Formation...
of New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
. Adult Bistahieversor are estimated to have been around 9 metres (29.5 ft) long, weighing at least a ton. The snout is deep, indicating that the feature is not unique to more derived
Derived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
tyrannosaurs such as Tyrannosaurus
Tyrannosaurus
Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...
. Geographical barriers such as the newly forming Rocky Mountains
Rocky Mountains
The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...
may have isolated the more southerly Bistahieversor from more derived northern tyrannosaurs.
Bistahieversor differs from other tyrannosaurs in the possession of 64 teeth, an extra opening above the eye, and a keel along the lower jaw. 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, preventing movement at the joint.
History of discovery
The first remains now attributed to Bistahieversor, a partial skull and skeleton, were described in 1990 as a specimen of AublysodonAublysodon
Aublysodon is a name given to a large number of carnivorous dinosaur teeth of a certain form found in numerous late Cretaceous period geological formations...
. Additional remains, consisting of the incomplete skull and skeleton of a juvenile, were described in 1992. Another, complete, skull and partial skeleton were found in the Bisti/De-Na-Zin Wilderness
Bisti/De-Na-Zin Wilderness
The Bisti/De-Na-Zin Wilderness is a wilderness area located in San Juan County in the U.S. state of New Mexico. Established in 1984, the Wilderness is a desolate area of steeply eroded badlands managed by the Bureau of Land Management, with the exception of three parcels of private Navajo land...
of New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
in 1998. 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
Daspletosaurus
Daspletosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America between 77 and 74 million years ago, during the Late Cretaceous Period. Fossils of the only named species were found in Alberta, although other possible species from Alberta and Montana await...
. 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, which they named Bistahieversor sealeyi.