Anasazisaurus
Encyclopedia
Anasazisaurus is a genus
of hadrosaurid
("duckbill") ornithopod
dinosaur
that lived about 74 million years ago, in the Late Cretaceous
Period. It was found in the Farmington Member of the Kirtland Formation
, in the San Juan
Basin of New Mexico
, United States
. Only a partial skull has been found to date. It was first described as a specimen of Kritosaurus by Jack Horner
, and has been intertwined with Kritosaurus
since its description. It is known for its short nasal
crest, which stuck out above and between its eyes for a short distance.
, and was only recently fully prepared. It has a sort of tab or flange of bone, from the nasals, that rises between and above the eyes and folds back under itself. This unique crest allows it to be distinguished from similar hadrosaurs, like Gryposaurus
. The top of the crest is roughened, and the maximum preserved length of the skull is ~90 centimeters (~35 in).
. If it is the same as Kritosaurus, Kritosaurus would be used because it is the older name.
, American
paleontologists, named this dinosaur in 1993. Its name is derived from the Anasazi, an ancient Native American
people, and the Greek
word sauros ("lizard"). The Anasazi were famous for their cliff-dwelling
s, such as those in Chaco Canyon
, near the location of fossil
Anasazisaurus remains. The term "Anasazi" itself is actually a Navajo language
word, anaasází ("enemy ancestors"). There is one known species
(A. horneri), which is named in honor of Jack Horner
, an influential paleontologist who first described the skull in 1992. The holotype
skull (and only known specimen) was collected in the late 1970s by a Brigham Young University
field party working in San Juan County
, and is housed at BYU as BYU 12950.
There is some debate over whether it is actually a valid genus. Horner originally assigned the skull to Kritosaurus navajovius
. Later, Hunt and Lucas could not find any diagnostic features on the limited material of Kritosaurus and judged the genus to be a nomen dubium
. Since the skull in question does have diagnostic features of its own, and did not appear to share any unique features with Kritosaurus, it was given the new name Anasazisaurus horneri. Some later authors, including those of the most recent review, have supported this decision. However, others have referred Anasazisaurus back to Kritosaurus, including Thomas Williamson, who has made the most detailed published case. Neither genus is well known, so further clarification of the status of all taxa involved will become more clear if new fossil material is discovered and prepared.
, which is one of the lower members. This formation dates from the late Campanian
stages of the Late Cretaceous
Period (74 to 70 million years ago), and is also the source of several other dinosaurs, like Alamosaurus
, Pentaceratops
, Nodocephalosaurus
, Saurornitholestes
, and as-yet-unnamed tyrannosaurids.
As a hadrosaurid, Anasazisaurus would have been a large bipedal/quadruped
al herbivore
, eating plants with a sophisticated skull that permitted a grinding motion analogous to chewing
. Its teeth
were continually replacing and packed into dental batteries that contained hundreds of teeth, only a relative handful of which were in use at any time. Plant material would have been cropped by its beak, and held in the jaws by a muscular cheek
. Feeding would have been from the ground up to ~4 meters (13 ft) above.
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 hadrosaurid
Hadrosaurid
Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...
("duckbill") ornithopod
Ornithopod
Ornithopods or members of the clade Ornithopoda are a group of ornithischian dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American...
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...
that lived about 74 million years ago, in 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...
Period. It was found in the Farmington Member of the Kirtland Formation
Kirtland 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...
, in the San Juan
San Juan, New Mexico
San Juan is a census-designated place in Rio Arriba County, New Mexico, United States. The population was 592 at the 2000 census.-Geography:San Juan is located at , a few miles north of Espanola....
Basin 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...
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. Only a partial skull has been found to date. It was first described as a specimen of Kritosaurus by Jack Horner
Jack Horner (paleontologist)
John "Jack" R. Horner is an American paleontologist who discovered and named Maiasaura, providing the first clear evidence that some dinosaurs cared for their young. He is one of the best-known paleontologists in the United States...
, and has been intertwined with Kritosaurus
Kritosaurus
Kritosaurus is an incompletely known but historically important genus of hadrosaurid dinosaur. It lived about 73 million years ago, in the Late Cretaceous of North America...
since its description. It is known for its short nasal
Nasal bone
The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
crest, which stuck out above and between its eyes for a short distance.
Description
The anatomy of Anasazisaurus is poorly known. The skull is somewhat poorly preserved, lacks the lower jaw, beak, and quadrateQuadrate bone
The quadrate bone is part of a skull in most tetrapods, including amphibians, sauropsids , and early synapsids. In these animals it connects to the quadratojugal and squamosal in the skull, and forms part of the jaw joint .- Evolutionary variation :In snakes, the quadrate bone has become elongated...
, and was only recently fully prepared. It has a sort of tab or flange of bone, from the nasals, that rises between and above the eyes and folds back under itself. This unique crest allows it to be distinguished from similar hadrosaurs, like Gryposaurus
Gryposaurus
Gryposaurus was a genus of duckbilled dinosaur that lived about 83 to 75.5 million years ago, in the Late Cretaceous of North America...
. The top of the crest is roughened, and the maximum preserved length of the skull is ~90 centimeters (~35 in).
Classification
Anasazisaurus is a hadrosaurine hadrosaurid, meaning it lacked a hollow crest. The most recent review recognized it as distinct, but did not try to place it beyond HadrosaurinaeHadrosaurinae
Saurolophinae is a subfamily of hadrosaurid dinosaurs. Members of the subfamily derive from the Late Cretaceous of Antarctica, Argentina, Canada , China, Kazakhstan, Mexico, Russia, the United States and...
. If it is the same as Kritosaurus, Kritosaurus would be used because it is the older name.
History
Adrian Hunt and Spencer G. LucasSpencer G. Lucas
Spencer George Lucas is an American paleontologist and stratigrapher, and curator of paleontology at the New Mexico Museum of Natural History and Science. His main areas of study are late Paleozoic, Mesozoic and early Cenozoic vertebrate fossils, stratigraphy, and continental deposits,...
, American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
paleontologists, named this dinosaur in 1993. Its name is derived from the Anasazi, an ancient Native American
Indigenous peoples of the Americas
The indigenous peoples of the Americas are the pre-Columbian inhabitants of North and South America, their descendants and other ethnic groups who are identified with those peoples. Indigenous peoples are known in Canada as Aboriginal peoples, and in the United States as Native Americans...
people, and the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
word sauros ("lizard"). The Anasazi were famous for their cliff-dwelling
Cliff-dwelling
Cliff dwelling is the general archaeological term for the habitations of prehistorical peoples, formed by using niches or caves in high cliffs, with more or less excavation or with additions in the way of masonry....
s, such as those in Chaco Canyon
Chaco Culture National Historical Park
Chaco Culture National Historical Park is a United States National Historical Park hosting the densest and most exceptional concentration of pueblos in the American Southwest. The park is located in northwestern New Mexico, between Albuquerque and Farmington, in a remote canyon cut by the Chaco Wash...
, near the location of fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
Anasazisaurus remains. The term "Anasazi" itself is actually a Navajo language
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...
word, anaasází ("enemy ancestors"). There is one known species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
(A. horneri), which is named in honor of Jack Horner
Jack Horner (paleontologist)
John "Jack" R. Horner is an American paleontologist who discovered and named Maiasaura, providing the first clear evidence that some dinosaurs cared for their young. He is one of the best-known paleontologists in the United States...
, an influential paleontologist who first described the skull in 1992. The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
skull (and only known specimen) was collected in the late 1970s by a Brigham Young University
Brigham Young University
Brigham Young University is a private university located in Provo, Utah. It is owned and operated by The Church of Jesus Christ of Latter-day Saints , and is the United States' largest religious university and third-largest private university.Approximately 98% of the university's 34,000 students...
field party working in San Juan County
San Juan County, New Mexico
-2010:Whereas according to the 2010 U.S. Census Bureau:*51.6% White*0.6% Black*36.6% Native American*0.4% Asian*0.1% Native Hawaiian or Pacific Islander*3.5% Two or more races*7.2% Other races*19.1% Hispanic or Latino -2000:...
, and is housed at BYU as BYU 12950.
There is some debate over whether it is actually a valid genus. Horner originally assigned the skull to Kritosaurus navajovius
Kritosaurus
Kritosaurus is an incompletely known but historically important genus of hadrosaurid dinosaur. It lived about 73 million years ago, in the Late Cretaceous of North America...
. Later, Hunt and Lucas could not find any diagnostic features on the limited material of Kritosaurus and judged the genus to be a nomen dubium
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
. Since the skull in question does have diagnostic features of its own, and did not appear to share any unique features with Kritosaurus, it was given the new name Anasazisaurus horneri. Some later authors, including those of the most recent review, have supported this decision. However, others have referred Anasazisaurus back to Kritosaurus, including Thomas Williamson, who has made the most detailed published case. Neither genus is well known, so further clarification of the status of all taxa involved will become more clear if new fossil material is discovered and prepared.
Paleoecology and paleobiology
Anasazisaurus was discovered in the Farmington Member of 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...
, which is one of the lower members. This formation dates from the late Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
stages of 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...
Period (74 to 70 million years ago), and is also the source of several other dinosaurs, like Alamosaurus
Alamosaurus
Alamosaurus is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period of what is now North America. It was a large quadrupedal herbivore. Isolated vertebrae and limb bones indicate that it reached sizes comparable to Argentinosaurus and Puertasaurus, which would make it the...
, Pentaceratops
Pentaceratops
Pentaceratops is a genus of ceratopsid dinosaur from the late Cretaceous Period of what is now North America. The appearance of Pentaceratops sternbergii in the fossil record marks the end of the Judithian land vertebrate age and the start of the Kirtlandian...
, Nodocephalosaurus
Nodocephalosaurus
Nodocephalosaurus is a genus of herbivorous ankylosaurine ankylosaurid dinosaur from Upper Cretaceous deposits of San Juan Basin, New Mexico. The holotype was recovered from the Late Campanian De-na-zin Member of the Kirtland Formation and consists of an incomplete skull...
, Saurornitholestes
Saurornitholestes
Saurornitholestes is a genus of carnivorous dromaeosaurid theropod dinosaur from the late Cretaceous of Alberta, Montana and New Mexico....
, and as-yet-unnamed tyrannosaurids.
As a hadrosaurid, Anasazisaurus would have been a large bipedal/quadruped
Quadruped
Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
al herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
, eating plants with a sophisticated skull that permitted a grinding motion analogous to chewing
Mastication
Mastication or chewing is the process by which food is crushed and ground by teeth. It is the first step of digestion and it increases the surface area of foods to allow more efficient break down by enzymes. During the mastication process, the food is positioned between the teeth for grinding by...
. Its teeth
Tooth
Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...
were continually replacing and packed into dental batteries that contained hundreds of teeth, only a relative handful of which were in use at any time. Plant material would have been cropped by its beak, and held in the jaws by a muscular cheek
Cheek
Cheeks constitute the area of the face below the eyes and between the nose and the left or right ear. They may also be referred to as jowls. "Buccal" means relating to the cheek. In humans, the region is innervated by the buccal nerve...
. Feeding would have been from the ground up to ~4 meters (13 ft) above.