Kritosaurus
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2008-06-23T21:20:42Z
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{{Taxobox
| name = ''Kritosaurus''
| image = Kritosaurus_BW.jpg
| image_width = 225px
| image_caption = ''Kritosaurus''
| fossil_range = [[Late Cretaceous]]
| regnum = [[Animal]]ia
| phylum = [[Chordate|Chordata]]
| classis = [[Sauropsid]]a
| superordo = [[Dinosaur]]ia
| ordo = [[Ornithischia]]
| subordo = [[Ornithopoda]]
| infraordo = [[Iguanodont]]ia
| superfamilia = [[Hadrosauroidea]]
| familia = [[Hadrosauridae]]
| subfamilia = [[Hadrosaurinae]]
| tribus = [[Saurolophini]]
| genus = '''''Kritosaurus'''''
| genus_authority = [[Barnum Brown|Brown]], 1910
| subdivision_ranks = [[Species]]
| subdivision =
* ''K. navajovius'' <small>([[type species]]) {{Taxobox authority |author=[[Barnum Brown|Brown]] |date=1910}}</small>
* ?"K." ''australis'' <small>[[José Bonaparte|Bonparte]], Franchi, Powell, and Sepulveda, 1984</small>
}}
'''''Kritosaurus''''' (meaning "separated lizard"; sometimes misinterpreted as "noble lizard", in reference to the presumed "[[hooknose|Roman nose]]";<ref name=BC06>{{cite book |last=Creisler |first=Benjamin S. |year=2006 |chapter=Deciphering duckbills |editor=Carpenter, Kenneth (ed.) |title=Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs |publisher=Indiana University Press |location=Bloomington and Indianapolis |pages=185-210 |isbn=0-253-34817-X}}</ref> the nasal region was fragmented, disarticulated, and originally restored flat) is an incompletely known but historically important [[genus]] of [[hadrosaurid]] (duckbilled) [[dinosaur]]. It lived about 73 million years ago, in the [[Late Cretaceous]] of [[North America|North]] and possibly [[South America]]. Its [[taxonomy|taxonomic]] history is convoluted, also incorporating ''[[Gryposaurus]]'', ''[[Anasazisaurus]]'', and ''[[Naashoibitosaurus]]''; this tangle will remain unresolved until better remains of ''Kritosaurus'' are described. Despite the dearth of material, this [[herbivore]] appeared in dinosaur books until the 1990s, although what was usually represented was the much more completely known ''Gryposaurus'', then thought to be a synonym.
==Description==
''Kritosaurus'' is only definitely determined from a partial skull and lower jaws, and associated undescribed [[postcrania]]l remains.<ref name=HWF04>{{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 }}</ref> The greater portion of the muzzle and [[premaxilla|upper beak]] are missing, but additional reconstruction in the early 2000s using fragments from the skull that had not been placed before show part of a crest in front of the eyes;<ref name=JIKetal06>{{cite book |last=Kirkland |first=James I. |coauthors=Hernández-Rivera, René; Gates, Terry; Paul, Gregory S.; Nesbitt, Sterling; Serrano-Brañas, Claudia Inés; and Garcia-de la Garza, Juan Pablo |year=2006 |chapter=Large hadrosaurine dinosaurs from the latest Campanian of Coahuila, 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=299-315}}</ref> the form of the crest is unknown at this point. The length of the skull is estimated at 87 [[centimetre|centimeters]] (34 [[inch|in]]) from the tip of the upper beak to the base of the [[quadrate bone|quadrate]] that articulates with the lower jaw at the back of the skull.<ref name=LW42a>{{cite book |last=Lull |first=Richard Swann |authorlink=Richard Swann Lull |coauthors= and Wright, Nelda E. |title=Hadrosaurian Dinosaurs of North America |year=1942 |publisher=Geological Society of America |series=Geological Society of America Special Paper '''40''' |pages=226 }}</ref> Potential [[autapomorphy|diagnostic characteristics]] of ''Kritosaurus'' include a [[predentary]] (lower beak) without tooth-like crenulations, a sharp downward bend to the lower jaws near the beak, and a heavy, somewhat rectangular [[maxilla]] (upper tooth-bearing bone).<ref name=JIKetal06/> If it turns out to be the same as ''Anasazisaurus'' or ''Naashoibitosaurus'', then the form of the complete crest is that of a tab or flange beginning in front of the eyes and rising between and above them, but not extended beyond them.
==Classification==
''Kritosaurus'' was a [[hadrosaurinae|hadrosaurine]] [[hadrosaurid]], a flat-headed or solid-crested duckbill. Because it is poorly known, its closest relatives are not yet known. ''Naashoibitosaurus'' and "K." ''australis'', both of which appear to be very similar, form a [[clade]] with ''[[Saurolophus]]'' in the most recent review of duckbill [[phylogeny]]. In the same work, ''Kritosaurus'' is confusingly considered both as distinct at the species level and as a [[nomen dubium|dubious name]].<ref name=HWF04/> Location and time separate ''Kritosaurus'' and the slightly older, primarily Canadian ''Gryposaurus'', along with some cranial details.<ref name=JIKetal06/>
==Discovery and history==
[[Image:Kritooriginal.jpg|thumb|225px|right|Barnum Brown's initial flatheaded reconstruction of the skull of ''Kritosaurus''.]]
In 1904, [[Barnum Brown]] discovered the [[holotype|type]] specimen ([[American Museum of Natural History|AMNH]] 5799) of ''Kritosaurus'' near [[Ojo Alamo]], [[San Juan County, New Mexico|San Juan County]], [[New Mexico]], [[United States]], while following up on a previous expedition.<ref name=BB10>{{cite journal |last=Brown |first=Barnum |authorlink=Barnum Brown |year=1910 |title=The Cretaceous Ojo Alamo beds of New Mexico with description of the new dinosaur genus ''Kritosaurus'' |journal=Bulletin of the American Museum of Natural History |volume=28 |issue=24 |pages=267–274 |url=http://digitallibrary.amnh.org/dspace/handle/2246/1398 }}</ref> He initially could not definitely correlate the [[stratigraphy]], but by 1916 was able to establish it as from what is now known as the [[Campanian|late Campanian]]-age De-na-zin Member of the [[Kirtland Formation]].<ref name=CWG16>{{cite journal |last=Gilmore |first=Charles W. |authorlink=Charles Whitney Gilmore |year=1916 |title=Contributions to the geology and paleontology of San Juan County, New Mexico. 2. Vertebrate faunas of the Ojo Alamo, Kirtland and Fruitland Formations |journal=United States Geological Survey Professional Paper |volume=98-Q |pages=279–302 }}</ref><ref name=TEW00>{{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}}</ref> When discovered, much of the front of the skull had either eroded or fragmented, and Brown reconstructed this portion after what is now called ''[[Anatotitan]]'', leaving out many fragments.<ref name=BB10/> However, he had noticed that something was different about the fragments, but ascribed the differences to crushing.<ref name=SG14>{{cite journal |last=Sinclair |first=William J. |coauthors=and Granger, Walter |year=1914 |title=Paleocene deposits of the San Juan Basin, New Mexico |journal=Bulletin of the American Museum of Natural History|volume=33 |pages=297–316 }}</ref> He initially wanted to name it ''[[Nectosaurus]]'', but found out that this name was already in use; Jan Versluys, who'd visited Brown before the change, inadvertently leaked the previous choice.<ref name=GO99>{{cite web |url=http://dml.cmnh.org/1999Nov/msg00560.html |title=Re: What are these dinosaurs? 2: Return of What are these dinosaurs? |accessdate=2007-06-15 |author=Olshevsky, George |authorlink=George Olshevsky |date=1999-11-17 |publisher=Dinosaur Mailing List }}</ref> He kept the species name, though, leading to the combination ''K. navajovius''.
The 1914 publication of the arch-snouted Canadian genus ''Gryposaurus''<ref name=LL14>{{cite journal |last=Lambe |first=Lawrence M. |authorlink=Lawrence Lambe |year=1914 |title=On ''Gryposaurus notabilis'', a new genus and species of trachodont dinosaur from the Belly River Formation of Alberta, with a description of the skull of ''Chasmosaurus belli'' |journal=The Ottawa Naturalist |volume=27 |issue=11 |pages=145–155 }}</ref> changed Brown's mind about the anatomy of his dinosaur's snout. Going back through the fragments, he revised the previous reconstruction and gave it a ''Gryposaurus''-like arched [[nasal bone|nasal]] crest.<ref name=SG14/> He also synonymized ''Gryposaurus'' with ''Kritosaurus'',<ref name=BB14>{{cite journal |last=Brown |first=Barnum |authorlink=Barnum Brown |year=1914 |title=Cretaceous Eocene correlation in New Mexico, Wyoming, Montana, Alberta |journal=Geological Society of America Bulletin |volume=33 |pages=355–380 |url=http://digitallibrary.amnh.org/dspace/handle/2246/704 }}</ref> a move supported by [[Charles Whitney Gilmore|Charles Gilmore]].<ref name=CWG16/> This synonymy was used through the 1920s ([[William Parks]]'s designation of a [[Canada|Canadian]] species as ''Kritosaurus incurvimanus'')<ref name=WAP20>{{cite journal |last=Parks |first=William A. |authorlink=William Parks |year=1920 |title=The osteology of the trachodont dinosaur ''Kritosaurus incurvimanus'' |journal=University of Toronto Studies, Geology Series |volume=11 |pages=1–76}}</ref> and became standard after the publication of [[Richard Swann Lull]] and [[Nelda Wright]]'s influential 1942 [[monograph]] on North American hadrosaurids.<ref name=LW42b>{{cite book |last=Lull |first=Richard Swann |authorlink=Richard Swann Lull |coauthors= and Wright, Nelda E. |title=Hadrosaurian Dinosaurs of North America |year=1942 |publisher=Geological Society of America |series=Geological Society of America Special Paper '''40''' |pages=164-172}}</ref> From this time until 1990, ''Kritosaurus'' would be composed of at least the [[type species]] ''K. navajovius'', ''K. incurvimanus'', and ''K. notabilis'', the former type species of ''Gryposaurus''. The poorly known species ''[[Hadrosaurus|Hadrosaurus breviceps]]'' ([[Othniel Charles Marsh|Marsh]], 1889),<ref name=OCM89>{{cite journal |last=Marsh |first=O.C. |authorlink=Othniel Charles Marsh |year=1889 |title=Notice of new American Dinosauria |journal=American Journal of Science |volume=38 |pages=331–336}}</ref> known from a [[dentary]] from the Campanian-age [[Judith River Formation]] of [[Montana]], was also assigned to ''Kritosaurus'' by Lull and Wright,<ref name=LW42b/> but this is no longer accepted.<ref name=HWF04/><ref name=PMWH06>{{cite journal |last=Prieto-Márquez |first=Alberto |coauthors=Weishampel, David B.; and Horner, John R. |year=2006 |title=The dinosaur ''Hadrosaurus foulkii'', from the Campanian of the East Coast of North America, with a reevaluation of the genus |journal=Acta Palaeontologica Polonica |volume=51 |issue=1 |pages=77–98 |url=http://app.pan.pl/acta51/app51-077.pdf |format={{dead link|date=June 2008}} – <sup>[http://scholar.google.co.uk/scholar?hl=en&lr=&q=author%3APrieto-M%C3%A1rquez+intitle%3AThe+dinosaur+%27%27Hadrosaurus+foulkii%27%27%2C+from+the+Campanian+of+the+East+Coast+of+North+America%2C+with+a+reevaluation+of+the+genus&as_publication=Acta+Palaeontologica+Polonica&as_ylo=2006&as_yhi=2006&btnG=Search Scholar search]</sup>}}</ref>
By the late 1970s and early 1980s, ''[[Hadrosaurus]]'' had entered the discussion as a possible synonym of either ''Kritosaurus'', ''Gryposaurus'', or both, particularly in semi-technical "dinosaur dictionaries".<ref name=DFG82>{{cite book |last=Glut |first=Donald F. |title=The New Dinosaur Dictionary |year=1982 |publisher=Citadel Press |location=Secaucus, NJ |isbn=0-8065-0782-9 |pages=158 }}</ref><ref name=DL83>{{cite book |last=Lambert |first=David |coauthors=and the Diagram Group |title=A Field Guide to Dinosaurs |year=1983 |publisher=Avon Books |location=New York |isbn=0-380-83519-3 |pages=161 }}</ref> One well-known work, [[David B. Norman]]'s ''The Illustrated Encyclopedia of Dinosaurs'', uses ''Kritosaurus'' for the Canadian material (''Gryposaurus''), but confusingly identifies the mounted skeleton of ''K. incurvimanus'' as ''Hadrosaurus''.<ref name=DBN85>{{cite book |last=Norman |first=David. B. |authorlink=David B. Norman |title=The Illustrated Encyclopedia of Dinosaurs: An Original and Compelling Insight into Life in the Dinosaur Kingdom |chapter=Hadrosaurids I|year=1985 |publisher=Crescent Books |location=New York |pages=116-121 |isbn=0-517-468905 }}</ref> One more species was added to ''Kritosaurus'' in these years. In 1984, [[Argentine]] [[paleontologist]] [[José Bonaparte]] and colleagues named ''K. australis'' for hadrosaur bones from the late Campanian-[[Maastrichtian|early Maastrichtian]] [[Los Alamitos Formation]] of [[Rio Negro Province|Rio Negro]], [[Patagonia]], [[Argentina]].<ref name=JBetal84>{{cite journal |last=Bonaparte |first=José |authorlink=José Bonaparte |coauthors=Franchi, M.R.; Powell, J.E.; and Sepulveda, E. |year=1984 |title=La Formación Los Alamitos (Campaniano-Maastrichtiano) del sudeste de Rio Negro, con descripcion de ''Kritosaurus australis'' n. sp. (Hadrosauridae). Significado paleogeografico de los vertebrados |journal=Revista de la Asociación Geología Argentina |language=Spanish |volume=39 |issue=3-4 |pages=284–299}}</ref> This species has been problematic and may not belong in ''Kritosaurus'', as suggested by the reviews in both editions of ''The Dinosauria''.<ref name=WH90>{{cite book |last=Weishampel |first=David B. |authorlink=David B. Weishampel |coauthors=and Horner, Jack R. |editor= Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.)|title=The Dinosauria |edition=1st |year=1990 |publisher=University of California Press |location=Berkeley |isbn=0-520-06727-4 |pages=534-561 |chapter=Hadrosauridae}}</ref><ref name=HWF04/>
The history of ''Kritosaurus'' took another turn in 1990, when [[Jack Horner (paleontologist)|Jack Horner]] and [[David B. Weishampel]] once again separated ''Gryposaurus'', citing the uncertainty associated with the latter's partial skull. Horner in 1992 described two more skulls from New Mexico that he claimed belonged to ''Kritosaurus'' and showed that it was quite different from ''Gryposaurus'',<ref name=JRH92>{{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 }}</ref> but the following year [[Adrian Hunt]] and [[Spencer G. Lucas]] put each skull in its own genus, creating ''[[Anasazisaurus]]'' and ''[[Naashoibitosaurus]]''.<ref name=HL93>{{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}}</ref> Not all authors have agreed with this, [[Thomas E. Williamson]] in particular defending Horner's original interpretation.<ref name=TEW00/> At least two recent publications have upheld the different genera, for now.<ref name=SGLetal06>{{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}}</ref><ref name=JIKetal06/>
Finally, the geographic range of potential ''Kritosaurus'' remains in North America has expanded. Bones from the late Campanian-age [[Aguja Formation]] of [[Texas]], including a skull, have been found.<ref name=JTS01>{{cite journal |last=Sankey |first=Julia T. |year=2001 |title=Late Campanian southern dinosaurs, Aguja Formation, Big Bend, Texas |journal=Journal of Paleontology |volumes=75 |pages=208–215 |doi=10.1666/0022-3360(2001)075<0208:LCSDAF>2.0.CO;2 |volume=75}}</ref><ref name=WL01>{{cite journal |last=Wagner |first=Jonathan R. |coauthors=and Lehman, Thomas M. |year=2001 |title=A new species of ''Kritosaurus'' from the Cretaceous of Big Bend National Park, Brewster County, Texas |journal=Journal of Vertebrate Paleontology |volume=21 |issue=3, Suppl. |pages=110A–111A}}</ref> Additionally, newly-described remains from [[Coahuila]], [[Mexico]] may represent a new species, one about 20% larger than ''K. navajovius'' (around 11 meters [36 ft] long) and with a distinctively curved [[ischium]]. This animal would be the largest known well-documented North American hadrosaurine. Unfortunately, the nasal bones are also incomplete in the skull remains from this material.<ref name=JIKetal06/>
==Paleoecology==
''Kritosaurus'' was discovered in the De-na-zin Member of the [[Kirtland Formation]]. This formation dates from the late [[Campanian]] stages of the [[Late Cretaceous]] Period (74 to 70 million years ago),<ref name=TEW00/> and is also the source of several other dinosaurs, like ''[[Alamosaurus]]'', a species of ''[[Parasaurolophus]]'', ''[[Pentaceratops]]'', ''[[Nodocephalosaurus]]'', ''[[Saurornitholestes]]'', and as-yet-unnamed [[tyrannosaurid]]s.<ref name=WETAL04>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.</ref> The Kirtland Formation is interpreted as [[river]] floodplains appearing after a retreat of the [[Western Interior Seaway]]. [[Conifer]]s were the dominant plants, and [[Ceratopsidae|chasmosaurine]] horned dinosaurs appear to have been more common than hadrosaurids.<ref name=DAR89>{{cite book |last=Russell |first=Dale A. |authorlink=Dale Russell |title=An Odyssey in Time: Dinosaurs of North America |year=1989 |publisher=NorthWord Press, Inc. |location=Minocqua, Wisconsin |isbn=1-55971-038-1 |pages=160-164}}</ref>
==Paleobiology==
===Diet and feeding===
As a hadrosaurid, ''Kritosaurus'' would have been a large [[bipedalism|bipedal]]/[[quadruped]]al [[herbivore]], eating [[plant]]s with a sophisticated skull that permitted a grinding motion analogous to [[mastication|chewing]]. Its [[tooth|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 broad beak, and held in the jaws by a [[cheek]]-like organ. Feeding would have been from the ground up to ~4 [[metre|meters]] (13 [[foot (unit of length)|ft]]) above.<ref name=HWF04/> If it was a separate genus, how it would have partitioned resources with the similar and contemporaneous ''Naashoibitosaurus'' is unknown.
===Nasal crest===
The nasal crest of ''Kritosaurus'', whatever its true form, may have been used for a variety of social functions, such as identification of sexes or species and social ranking.<ref name=HWF04/> There may have been inflatable air sacs flanking it for both visual and auditory signaling.<ref name=JAH75>{{cite journal |last=Hopson |first=James A. |year=1975 |title=The evolution of cranial display structures in hadrosaurian dinosaurs |journal=Paleobiology |volume=1 |issue=1 |pages=21–43 }}</ref>
==In popular culture==
The synonymization of ''Kritosaurus'' and ''Gryposaurus'' that lasted from the 1910s to 1990 led to a distorted picture of what the original ''Kritosaurus'' material represented. Because the Canadian material was much more complete, most representations and discussions of ''Kritosaurus'' from the 1920s to 1990 are actually more applicable to ''Gryposaurus''. This includes, for example, James Hopson's discussion of hadrosaur cranial ornamentation,<ref name=JAH75/> and the adaptation of this for the public in ''The Illustrated Encyclopedia of Dinosaurs''.<ref name=DBN85b>{{cite book |last=Norman |first=David B. |authorlink=David B. Norman |title=The Illustrated Encyclopedia of Dinosaurs: An Original and Compelling Insight into Life in the Dinosaur Kingdom|chapter=Hadrosaurids II |year=1985 |publisher=Crescent Books |location=New York|pages=122-127 |isbn=0-517-468905 }}</ref>
==References==
{{reflist|2}}
==External links==
{{portalpar|Dinosaurs}}
* [http://www.dinoruss.com/de_4/5a7b0d6.htm ''Kritosaurus'' in The Dinosaur Encyclopaedia] at Dino Russ' Lair
[[Category:Cretaceous dinosaurs]]
[[Category:Dinosaurs of North America]]
[[Category:Dinosaurs of South America]]
[[Category:Hadrosaurs]]
[[Category:San Juan County, New Mexico]]
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