Anasazisaurus

Taxobox|
name = "Anasazisaurus"
fossil_range = Late Cretaceous
regnum = Animalia
phylum = Chordata
classis = Sauropsida
superordo = Dinosauria
ordo = Ornithischia
subordo = Ornithopoda
infraordo = Iguanodontia
familia = Hadrosauridae
subfamilia = Hadrosaurinae
genus = "Anasazisaurus"
genus_authority = Hunt and Lucas, 1993
subdivision_ranks = Species
subdivision = "A. horneri" Hunt and Lucas, 1993

"Anasazisaurus" (pronEng|ˌɑːnəˌsɑːziːˈsɔrəs AHN-ah-SAH-zee-SAWR-us; "Anasazi lizard") 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.

Description

The anatomy of "Anasazisaurus" is poorly known. The skull is somewhat poorly preserved, lacks the lower jaw, beak, and quadrate, and was only recently fully prepared.cite book |last=Lucas |first=Spencer G. |authorlink=Spencer G. Lucas |coauthors=Spielman, Justin A.; Sullivan, Robert M.; Hunt, Adrian P.; and Gates, Terry |year=2006 |chapter="Anasazisaurus", a hadrosaurian dinosaur from the Upper Cretaceous of New Mexico |editor=Lucas, S.G.; and Sullivan, Robert M. (eds.) |title=Late Cretaceous Vertebrates from the Western Interior |series=New Mexico Museum of Natural History and Science Bulletin, 35 |publisher=New Mexico Museum of Natural History and Science |location=Albuqueque, New Mexico |pages=293-297] 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".cite journal |last=Horner |first=John R. |authorlink=Jack Horner (paleontologist) |year=1992 |title=Cranial morphology of "Prosaurolophus" (Ornithischia: Hadrosauridae) with descriptions of two new hadrosaurid species and an evaluation of hadrosaurid phylogenetic relationships |journal=Museum of the Rockies Occasional Paper |volume=2 |pages=1–119 ] 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 Hadrosaurinae.cite book |last=Horner |first=John R. |authorlink=Jack Horner (paleontologist) |coauthors=Weishampel, David B.; and Forster, Catherine A |editor=Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.)|title=The Dinosauria |edition=2nd |year= 2004|publisher=University of California Press |location=Berkeley |isbn=0-520-24209-2 |pages=438-463 |chapter=Hadrosauridae ] If it is the same as "Kritosaurus", "Kritosaurus" would be used because it is the older name.

History

Adrian Hunt and Spencer G. Lucas, 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-dwellings, such as those in Chaco Canyon, near the location of fossil "Anasazisaurus" remains in. 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.cite book |last=Hunt |first=Adrian P. |coauthors=and Lucas, Spencer G. |year=1993 |chapter=Cretaceous vertebrates of New Mexico |editor=Lucas, S.G.; and Zidek, J. (eds.) |title=Dinosaurs of New Mexico |series=New Mexico Museum of Natural History and Science Bulletin, 2 |publisher=New Mexico Museum of Natural History and Science |location=Albuqueque, New Mexico |pages=77-91]

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.cite book |last=Williamson |first=Thomas E. |year=2000 |chapter=Review of Hadrosauridae (Dinosauria, Ornithischia) from the San Juan Basin, New Mexico |editor=Lucas, S.G.; and Heckert, A.B. (eds.) |title=Dinosaurs of New Mexico |series=New Mexico Museum of Natural History and Science Bulletin, 17 |publisher=New Mexico Museum of Natural History and Science |location=Albuqueque, New Mexico |pages=191-213] 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 Formation, 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.Weishampel, David B.; Barrett, Paul M.; Coria, Rodolfo A.; Le Loeuff, Jean; Xu Xing; Zhao Xijin; Sahni, Ashok; Gomani, Elizabeth, M.P.; and Noto, Christopher R. (2004). "Dinosaur Distribution". "The Dinosauria" (2nd). 517–606.]

As a hadrosaurid, "Anasazisaurus" would have been a large bipedal/quadrupedal 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 cheek-like organ. Feeding would have been from the ground up to ~4 meters (13 ft) above.

References