Chindesaurus
Encyclopedia
Chindesaurus is a genus
of saurischia
n dinosaur
named after Chinde Point (Chinde {Navajo
, chindi
} meaning "ghost or evil spirit"), near where the genoholotype specimen (a partial skeleton) was discovered in the Chinle Formation
of Petrified Forest National Park
, Arizona
, by Bryan Small in 1985. The Petrified Forest formation dates to the early Norian
stage of the late Triassic
period, about 216 million years ago. It was formally described by Long and Murry in 1995. The type species
, Chindesaurus bryansmalli, is named in honor of the discoverer.
is included). The type specimen is the most complete, and contains several rib and vertebrae fragments, two complete vertebrae from the hips and one from the tail, fragments of hip bones, and partial leg bones. A single tooth was also found with the specimen. The remaining specimens are even more incomplete, consisting of isolated hip bones and upper leg bones (femora), and more vertebrae.
The type and paratype specimens probably came from individuals around 2.4 metres (7.9 ft) in length.
, an opinion that has been followed by most paleontologists since. Phylogenetic analyses published through 2007 continued to find it to fall among the herrerasaurids, though a few studies cast doubt on this, including one in 2007 by Irmis, Nesbitt and colleagues which found Chindesaurus to be a probable basal
saurischian dinosaur, and noted that it shares a wide range of characteristics with several lineages of basal saurischians, making any classification problematic.
One specimen originally assigned to Chindesaurus, from the Tecovas Formation
of Texas
, was later placed in its own genus and species, Caseosaurus crosbyensis
. Subsequent research has shown that this separation was probably in error, and that the two forms represent the same species. Nesbitt, Irmis and Parker agreed in a 2007 paper that there is little reason to separate Caseosaurus from Chindesaurus, and the two even share some unique characteristics not found in similar species. Nesbitt and colleagues suggested that any differences between the two were probably related to differences in size. However, since both species are so fragmentary, they decided not to formally make them synonyms.
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 saurischia
Saurischia
Saurischia meaning 'lizard' and ischion meaning 'hip joint') is one of the two orders, or basic divisions, of dinosaurs. In 1888, Harry Seeley classified dinosaurs into two orders, based on their hip structure...
n 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...
named after Chinde Point (Chinde {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...
, chindi
Chindi
In Navajo religious belief, a chindi is the ghost left behind after a person dies, believed to leave the body with the deceased's last breath. It is everything that was bad about the person; the "residue that man has been unable to bring into universal harmony". Traditional Navajo believe that...
} meaning "ghost or evil spirit"), near where the genoholotype specimen (a partial skeleton) was discovered in the Chinle Formation
Chinle Formation
The Chinle is a geologic formation that is spread across the U.S. states of northern Arizona, Nevada, Utah, western New Mexico, and western Colorado. The Chinle is controversially considered to be synonymous to the Dockum Group in eastern Colorado, eastern New Mexico, southwestern Kansas, the...
of Petrified Forest National Park
Petrified Forest National Park
Petrified Forest National Park is a United States national park in Navajo and Apache counties in northeastern Arizona. The park's headquarters are about east of Holbrook along Interstate 40 , which parallels a railroad line, the Puerco River, and historic U.S. Route 66, all crossing the park...
, Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
, by Bryan Small in 1985. The Petrified Forest formation dates to the early Norian
Norian
The Norian is a division of the Triassic geological period. It has the rank of an age or stage . The Norian lasted from 216.5 ± 2.0 to 203.6 ± 1.5 million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.-Stratigraphic definitions:The Norian was named after the Noric Alps in...
stage of the late Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
period, about 216 million years ago. It was formally described by Long and Murry in 1995. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, Chindesaurus bryansmalli, is named in honor of the discoverer.
Description
Chindesaurus is known from five incomplete specimens (six if CaseosaurusCaseosaurus
Caseosaurus is a genus of dinosaur from the Late Triassic of North America. The type species, Caseosaurus crosbyensis, was formally described by Hunt, Lucas, Heckert, Sullivan and Lockley in 1998. It was found in the Dockum Formation of Texas, in strata dating to the Late Triassic...
is included). The type specimen is the most complete, and contains several rib and vertebrae fragments, two complete vertebrae from the hips and one from the tail, fragments of hip bones, and partial leg bones. A single tooth was also found with the specimen. The remaining specimens are even more incomplete, consisting of isolated hip bones and upper leg bones (femora), and more vertebrae.
The type and paratype specimens probably came from individuals around 2.4 metres (7.9 ft) in length.
Classification
Chindesaurus has been difficult to classify, and has been recovered in several different positions at the base of the saurischian family tree. When it was first discovered in 1985, the animal which would eventually be named Chindesaurus was thought to be a prosauropod. When it was finally described and named a decade after its discovery by Long and Murray, they regarded it as a herrerasauridHerrerasauridae
Herrerasaurids are among the oldest known dinosaurs, appearing in the fossil record 231.4 million years ago . They became extinct by the end of the Triassic period. Herrerasaurids were small-sized carnivorous theropods or basal saurischians...
, an opinion that has been followed by most paleontologists since. Phylogenetic analyses published through 2007 continued to find it to fall among the herrerasaurids, though a few studies cast doubt on this, including one in 2007 by Irmis, Nesbitt and colleagues which found Chindesaurus to be a probable basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
saurischian dinosaur, and noted that it shares a wide range of characteristics with several lineages of basal saurischians, making any classification problematic.
One specimen originally assigned to Chindesaurus, from the Tecovas Formation
Tecovas Formation
-Vertebrate fauna:...
of Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, was later placed in its own genus and species, Caseosaurus crosbyensis
Caseosaurus
Caseosaurus is a genus of dinosaur from the Late Triassic of North America. The type species, Caseosaurus crosbyensis, was formally described by Hunt, Lucas, Heckert, Sullivan and Lockley in 1998. It was found in the Dockum Formation of Texas, in strata dating to the Late Triassic...
. Subsequent research has shown that this separation was probably in error, and that the two forms represent the same species. Nesbitt, Irmis and Parker agreed in a 2007 paper that there is little reason to separate Caseosaurus from Chindesaurus, and the two even share some unique characteristics not found in similar species. Nesbitt and colleagues suggested that any differences between the two were probably related to differences in size. However, since both species are so fragmentary, they decided not to formally make them synonyms.
External links
- Image of Chindesaurus by Rob Gay
