Sauropelta
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{{Taxobox
| image = Sauropelta_jconway.png
| image_width = 220px
| name = ''Sauropelta''
| fossil_range = [[Early Cretaceous]]
| regnum = [[Animal]]ia
| phylum = [[Chordate|Chordata]]
| classis = [[Reptile|Sauropsida]]
| superordo = [[Dinosaur]]ia
| ordo = [[Ornithischia]]
| subordo = [[Thyreophora]]
| infraordo = [[Ankylosauria]]
| familia = [[Nodosauridae]]
| genus = '''''Sauropelta'''''
| genus_authority = [[John Ostrom|Ostrom]], 1970
| subdivision_ranks = [[Species]]
| subdivision =
*''S. edwardsorum'' <small>Ostrom, 1970 ([[Type (zoology)|type]])</small>
}}
'''''Sauropelta''''' ({{pronEng|ˌsɔroʊˈpɛltə}} or SAWR-o-''PEL''-ta; meaning 'lizard shield') is a [[genus]] of [[nodosaurid]] [[dinosaur]] that existed in the Early [[Cretaceous Period]] of [[North America]]. One [[species]] (''S. edwardsorum'') has been named although others may have existed. Anatomically, ''Sauropelta'' is one of the most well-understood nodosaurids, with [[fossil]]ized remains recovered in the [[U.S.]] states of [[Wyoming]], [[Montana]], and possibly [[Utah]]. It is also the earliest known genus of nodosaurid; most of its remains are found in the [[Cloverly Formation]], which dates to about 115 to 110 [[Mega-annum|Ma]] ([[million years ago]]).
It was a medium-sized nodosaurid, measuring about 5 [[meter]]s (16.5 [[Foot (unit of length)|ft]]) long. ''Sauropelta'' had a distinctively long tail which made up about half of its body length. Although its body was smaller than a modern [[black rhinoceros]], ''Sauropelta'' was about the same mass, weighing in at about 1500 [[kilograms]] (3300 [[pound (mass)|lb]]). The extra weight was largely due to its extensive bony [[Armour (zoology)|body armor]], including the characteristically large spines projecting from its neck.
==Description==
''Sauropelta'' was a heavily-built [[quadruped]]al [[herbivore]] with a body length of approximately 5 meters (16.5 ft).<ref name=carpenter1984>{{cite journal |last=Carpenter |first=Kenneth. |authorlink=Kenneth Carpenter |year=1984 |title=Skeletal reconstruction and life restoration of ''Sauropelta'' (Ankylosauria: Nodosauridae) from the Cretaceous of North America |journal=Canadian Journal of Earth Sciences |volume=21 |pages=1491–1498}}</ref> The [[skull]] was triangular when viewed from above, with the rear end wider than the tapering snout. One skull measured 35 [[centimeter]]s (13.75 [[inch|in]]) in width at its widest point, behind the eyes.<ref name=carpenterkirkland1998>{{cite book |last=Carpenter |first=Kenneth |authorlink=Kenneth Carpenter |coauthors=& [[James Kirkland (paleontologist)|Kirkland, James I.]] |year=1998 |chapter=Review of Lower and Middle Cretaceous Ankylosaurs from North America|editor= [[Spencer G. Lucas|Lucas, Spencer G.]]; Kirkland, James I; & Estep, J.W. (eds.). |title=Lower and Middle Cretaceous Ecosystems |series=''New Mexico Museum of Natural History and Science Bulletin'' '''14''' |pages=249-270}}</ref> Unlike some other nodosaurids, the roof of the skull was characteristically flat, not domed. The roof of the skull was very thick and covered in flat, bony plates that are so tightly fused that there appear to be no [[Cranial sutures|sutures]] (boundaries) like the ones seen in ''[[Panoplosaurus]]'', ''[[Pawpawsaurus]]'', ''[[Silvisaurus]]'', and many other ankylosaurs. This could also be an artifact of preservation or preparation. As in other ankylosaurs, thick triangular [[scute]]s projected from the [[postorbital]] bone, above and behind the eyes, as well as the [[jugal]] bone, below and behind the eyes.<ref name=carpenterkirkland1998/> More typically for nodosaurids, leaf-shaped teeth lined both upper and lower jaws, used for cutting plant material. The front end of the skull is unknown, but there would have been a sharp bony ridge ([[tomium]]) at the end of both upper and lower jaws, as seen in other ankylosaurs. This ridge probably would have supported a [[keratin]]ous [[beak]].<ref name=vickaryousetal2004>{{cite book |last=Vickaryous |first=Matthew K. |coauthors=Maryanska, Teresa; & [[David B. Weishampel|Weishampel, David B.]] |year=2004 |chapter=Ankylosauria |editor=Weishampel, David B.; [[Peter Dodson|Dodson, Peter]]; & Osmólska, Halszka (eds.). |title=The Dinosauria |edition=Second Edition |location = Berkeley |publisher = University of California Press |pages=363-392}}</ref>
[[Image:Sauropelta.png|left|thumb|200px|''Sauropelta edwardsorum'' with a human for scale.]]
The tail of ''Sauropelta'' was characteristically long and made up nearly half of the body length. One skeleton preserved forty caudal (tail) [[vertebra]]e, although some were missing, suggesting that the true number of caudal vertebrae may have exceeded fifty. [[Ossification|Ossified]] [[tendon]]s stiffened the tail along its length. Like other ankylosaurs, ''Sauropelta'' had a wide body, with a very broad pelvis and ribcage. The forelimbs were shorter than the hindlimbs, which resulted in an arched back, with the highest point over the hips. Its [[foot|feet]], limbs, [[shoulder]]s, and [[pelvis]] were all very stoutly constructed and reinforced to support a great deal of weight. American [[paleontologist]] [[Kenneth Carpenter|Ken Carpenter]] estimated the mass of ''S. edwardsorum'' at 1500 kilograms (3300 lb).<ref name=carpenter1984/>
Like other nodosaurids, ''Sauropelta'' was covered in armor formed from bony masses embedded in the skin ([[osteoderm]]s). The discovery of a skeleton with the body armor preserved ''[[in situ]]'' allowed Carpenter and other scientists to accurately describe this protection. Two [[parallel (geometry)|parallel]] rows of domed [[scute]]s ran down the top of the neck, along the [[Anatomical terms of location#Anterior and posterior|anteroposterior axis]] (front to back). On the upper surface of the back and tail, the skin was covered in small, bony nodules (''ossicles''), which separated larger conical scutes arranged in parallel rows along the [[Anatomical terms of location#Left and right .28lateral.29.2C and medial|mediolateral axis]] (side to side). Over the hips, the ossicles and larger domed plates were interlocked very tightly to form a structure called a sacral shield.<ref name=carpenter1984/> This shield is also found in ankylosaurs like ''[[Polacanthus]]'' and ''[[Antarctopelta]]''.<ref name=vickaryousetal2004/><ref name=salgadogasparini2006>{{cite journal |last=Salgado |first=Leonardo |coauthors=& Gasparini, Zulma. |year=2006 |title=Reappraisal of an ankylosaurian dinosaur from the Upper Cretaceous of James Ross Island (Antarctica). |journal=Geodiversitas |volume=28 |issue=1 |pages=119–135}}</ref> Dramatically large, pointed spines lined the sides of the neck, increasing in size towards the shoulders, and then decreasing in size again along the side of the body until they stopped just before the hips. Behind the hips, flat triangular plates lined the tail on both sides, pointing laterally (outwards) and decreasing in size towards the end of the tail. Carpenter originally described the cervical (neck) spines and caudal plates as belonging to a single row on each side, although more recently he and [[James Kirkland (paleontologist)|Jim Kirkland]] reconstructed them in two parallel rows on each side, one above the other. The upper row of cervical spines pointed backwards and upwards (posterodorsally), while the lower row pointed backwards and outwards (posterolaterally). The bases of each pair of cervical spines and each pair of caudal plates were fused together, greatly restricting mobility in both the neck and upper tail.<ref name=carpenterkirkland1998/>
==Classification and systematics==
[[Image:Sauropelta.gif|thumb|Skeleton.]]
Since John Ostrom first described ''Sauropelta'' in 1970, it has been recognized as a member of the [[family (biology)|family]] [[Nodosauridae]].<ref name=ostrom1970>{{cite journal |last=Ostrom |first=John H. |authorlink=John Ostrom |year=1970 |title=Stratigraphy and paleontology of the Cloverly Formation (Lower Cretaceous) of the Bighorn Basin area, Wyoming and Montana |journal=Bulletin of the Peabody Museum of Natural History |volume=35 |pages=1–234}}</ref> The nodosaurids, along with the family [[Ankylosauridae]], belong within the [[infraorder]] [[Ankylosauria]]. Nodosaurids are characterized by certain features of the skull, including the [[mandible]] (lower jaw), which curves downwards at the end. Overall, nodosaurids had narrower snouts than the ankylosaurids, and also lacked the heavy ankylosaurid tail clubs.<ref name=carpenter1997>{{cite book |last= Carpenter |first=Kenneth. |authorlink=Kenneth Carpenter |year=1997 |chapter=Ankylosauria |editor = [[Phil Currie|Currie, Philip J.]]; & Padian, Kevin (eds.). |title=The Encyclopedia of Dinosaurs |publisher = University of California Press |location = Berkeley |pages=16-17}}</ref> Nodosaurids are only found in North America and Europe, while ankylosaurids have also been found in [[Asia]].<ref name=vickaryousetal2004/><ref name=hilletal2003>{{cite journal |last=Hill |first=Robert V. |coauthors=Witmer, Lawrence M.; & Norell, Mark A. |year=2003 |title=A new specimen of ''Pinacosaurus grangeri'' (Dinosauria: Ornithischia) from the Late Cretaceous of Mongolia: Ontogeny and Phylogeny of Ankylosaurs. |journal=American Museum Novitates |volume=3395 |pages=1–29 |doi=10.1206/0003-0082(2003)395<0001:ANSOPG>2.0.CO;2 |doilabel=10.1206/0003-0082(2003)395<0001:ANSOPG>2.0.CO;2}}</ref>
While the [[systematics]] ([[evolution]]ary relationships) of nodosaurids have not been firmly established, the genera ''Sauropelta'', ''Silvisaurus'' and ''Pawpawsaurus'' are sometimes considered to be [[Basal (phylogenetics)|basal]] to geologically younger nodosaurids like ''Panoplosaurus'', ''[[Edmontonia]]'' and ''[[Animantarx]]''.<ref name=vickaryousetal2004/><ref name=hilletal2003/> In a 2001 analysis, Carpenter included the former three genera in a [[sister clade]] to a group containing the latter three, although he found that ''Panoplosaurus'' could belong to either clade, depending which [[taxa]] and characters were chosen.<ref name=carpenter2004>{{cite book |last= Carpenter |first=Kenneth. |authorlink=Kenneth Carpenter |year=2001 |chapter=Phylogenetic analysis of the Ankylosauria |editor = Carpenter, Kenneth (ed.). |title=The Armored Dinosaurs |pages=455-483 |publisher=Indiana University Press |location=Bloomington}}</ref>
==Discovery and naming==
In the early 1930s, famed dinosaur hunter and paleontologist [[Barnum Brown]] collected the [[holotype]] specimen of ''Sauropelta'' ('''AMNH 3032''', a partial skeleton) from the Cloverly Formation in [[Big Horn County, Montana|Big Horn County]], Montana. The locality is inside the [[Crow Indian Reservation]]. Brown also discovered two other specimens ('''AMNH 3035''' and '''3036'''). The latter is one of the best-preserved nodosaurid skeletons known to science, includes a large amount of ''in situ'' armor, and is on display in the [[American Museum of Natural History]] in [[New York City]]. AMNH 3035 preserves the cervical armor and most of a skull, missing only the end of the snout. Expeditions in the 1960s led by the equally renowned [[John Ostrom]] of [[Yale University]]'s [[Peabody Museum of Natural History]] recovered additional incomplete specimens from the Cloverly. In 1970, Ostrom coined the genus ''Sauropelta'' to include remains discovered by both expeditions. Derived from the [[Ancient Greek|Greek]] '''''σαυρος'''''/'''''sauros''''' ('lizard') and '''''πελτε'''''/'''''pelte''''' ('shield'), this name is a reference to its bony armor.<ref name=ostrom1970/> Although Ostrom originally named the species ''S. edwardsi'', [[binomial nomenclature|nomenclaturist]] [[George Olshevsky]] corrected the spelling to ''S. edwardsorum'' in 1991 to conform to [[Latin]] [[grammar]] rules.<ref name=olshevsky1991>{{cite book |author=Olshevsky, George. |authorlink=George Olshevsky |year=1991 |title=A Revision of the Parainfraclass Archosauria Cope, 1869, Excluding the Advanced Crocodylia. |series=Mesozoic Meanderings No. 2 |publisher=Publications Requiring Research |location=San Diego |pages=196pp}}</ref>
Despite the naming of ''Sauropelta'' two years earlier, confusion arose in 1972 when the name "Peltosaurus" was inadvertently published as the caption of a photograph of AMNH 3036.<ref name=glut1972>{{cite book |last=Glut |first=Donald F. |authorlink=Donald F. Glut |year=1972 |title=The Dinosaur Dictionary |publisher=Citadel Press |location=Secaucus |pages=217pp}}</ref> Although Brown never published a name or description for the remains which are now known as ''Sauropelta edwardsorum'', "Peltosaurus" was the name he informally used in lectures and museum exhibits. However, the name ''[[Peltosaurus]]'' was preoccupied by a genus of North American [[lizard]] from an [[extinct]] branch of the modern family [[Anguidae]] (the alligator lizards and the legless [[glass lizard]]s) and is no longer used to refer to the dinosaur.<ref name=churemcintosh1989>{{cite book |last=Chure |first=Daniel J. |coauthors=& McIntosh, John S. |year=1989 |title=A Bibliography of the Dinosauria (Exclusive of the Aves), 1677-1986 |series=''Paleontology Series'' '''1''' |publisher=Museum of Western Colorado |location=Grand Junction |pages=226pp}}</ref>
In 1999, Carpenter and colleagues described material of a large nodosaurid from Utah, discovered in a [[Geologic unit|member]] of the [[Cedar Mountain Formation]] called the Poison Strip Sandstone, which is contemporaneous with the Cloverly Formation. He originally referred it to ''Sauropelta'' as a possible new species, but it was never named.<ref name=carpenteretal1999>{{cite book |last=Carpenter |first=Kenneth |authorlink=Kenneth Carpenter |coauthors=[[James Kirkland (paleontologist)|Kirkland, James I.]]; Burge, Donald; & Bird, John. |year=1999 |chapter=Ankylosaurs (Dinosauria: Ornithischia) of the Cedar Mountain Formation, Utah, and their stratigraphic distribution |editor = [[David Gillette|Gillette, David]] (ed.). |title=Vertebrate Paleontology of Utah. |series=''Utah Geological Survey Miscellaneous Publication'' '''99-1''' |pages=244-251}}</ref> In more recent publications, Carpenter no longer refers the Poison Strip animal to ''Sauropelta'', only to the family Nodosauridae.<ref name=carpenter2006>{{cite book |last=Carpenter |first=Kenneth. |authorlink=Kenneth Carpenter |year=2006 |chapter=Assessing dinosaur faunal turnover in the Cedar Mountain Formation (Lower Cretaceous) of Eastern Utah, USA |editor=Barrett, Paul M.; & Evans, S.E (eds.). |title=Ninth International Symposium on Mesozoic Terrestrial Ecosystems and Biota |publisher = Natural History Museum |location = London |pages=21-25}}</ref>
Other recent, but undescribed, discoveries include a complete skull from the Cloverly of Montana<ref name=parsonsparsons2001>{{cite journal |last=Parsons |first=William L. |coauthors=& Parsons, Kristen M. |year=2001 |title=Description of a new skull of ''Sauropelta'' cf. ''S. edwardsi'' Ostrom, 1970 (Ornithischia: Ankylosauria) |journal=Journal of Vertebrate Paleontology |volume=21 |issue=Supplement to 3 - Abstracts of Papers, 61st Annual Meeting of the Society of Vertebrate Paleontology |pages=87A }}</ref> and a huge fragmentary skeleton from the Cedar Mountain Formation of Utah.<ref name=warrencarpenter2004>{{cite journal |last=Warren |first=David |coauthors=& [[Kenneth Carpenter|Carpenter, Kenneth]]. |year=2004 |title=A large nodosaurid ankylosaur from the Cedar Mountain Formation of Utah |journal=Journal of Vertebrate Paleontology |volume=24 |issue=Supplement to 3 - Abstracts of Papers, 64th Annual Meeting of the Society of Vertebrate Paleontology |pages=126A }}</ref> These discoveries have been published only as [[abstract (summary)|abstracts]] for the annual [[Society of Vertebrate Paleontology]] [[academic conference|conference]], and may or may not prove to belong to ''S. edwardsorum'' or even ''Sauropelta'' when formally published.
==Paleoecology==
''Sauropelta'' is the earliest known nodosaurid genus. All specimens of ''S. edwardsorum'' were recovered from the middle section of the Cloverly Formation in Wyoming and Montana, which dates to the late [[Aptian]] through early [[Albian]] [[faunal stage|stages]] of the [[Early Cretaceous]], or about 115 to 110 Ma (million years ago).<ref name=carpenterkirkland1998/><ref name=kirklandetal1997>{{cite journal |last=Kirkland |first=James I. |authorlink=James Kirkland (paleontologist) |coauthors=Britt, Brooks; Burge, Donald L.; [[Kenneth Carpenter|Carpenter, Kenneth]]; Cifelli, Richard; DeCourten, Frank; Eaton, Jeffrey; Hasiotis, Steven; & Lawton, Timothy. |year=1997 |title=Lower to Middle Cretaceous Dinosaur faunas of the central Colorado Plateau: a key to understanding 35 million years of tectonics, sedimentology, evolution, and biogeography |journal=Brigham Young University Geology Studies |volume=42 |issue=II |pages=69–103}}</ref> ''Sauropelta'' lived in wide floodplains around [[river]]s that drained into the shallow inland sea to the north and east, carrying sediment eroded from the low mountains to the west. Periodic flooding of these rivers covered the surrounding plains with new muddy sediments, creating the Cloverly Formation and burying the remains of many animals, some of which would be fossilized. At the end of Cloverly times, the shallow sea would expand to cover the entire region and would eventually split North America completely in half, forming the [[Western Interior Seaway]].<ref name=maxwell1997>{{cite book |last=Maxwell |first=W. Desmond. |year=1997 |chapter=Cloverly Formation |editor = [[Phil Currie|Currie, Philip J.]]; & Padian, Kevin (eds.). |title=The Encyclopedia of Dinosaurs |publisher=Academic Press |location=San Diego |pages=128-129}}</ref> Abundant fossil remains of [[conifer]]ous [[tree]]s suggest that these plains were covered in [[forest]]s.<ref name=ostrom1970/> [[Poaceae|Grasses]] would not evolve until later in the Cretaceous, so ''Sauropelta'' and other Early Cretaceous dinosaurian herbivores browsed from a variety of conifers and [[cycad]]s.<ref name=prasadetal2005>{{cite journal |last=Prasad |first=Vandana |coauthors=Strömberg, Caroline A.E.; Alimohammadian, Habib; & Sahni, Ashok. |year=2005 |title=Dinosaur coprolites and the early evolution of grasses and grazers |journal=Science |volume=310 |pages=1177–1180 |doi=10.1126/science.1118806}}</ref> Nodosaurids like ''Sauropelta'' had narrow snouts, an adaptation seen today in animals that are selective browsers as opposed to the wide muzzles of [[grazing|grazers]].<ref name=carpenter1997/>
While ''Sauropelta'' was an important part of the Cloverly herbivore [[Guild (ecology)|guild]], the most abundant herbivorous dinosaur of the time was the large [[ornithopod]] ''[[Tenontosaurus]]''. The smaller ornithopod ''[[Zephyrosaurus]]'', rare [[titanosaur]] [[sauropod]]s, and an unknown type of [[ornithomimosaur]] also lived alongside ''Sauropelta''. The [[dromaeosaurid]] [[theropod]] ''[[Deinonychus]]'' fed upon some of these herbivores, and the sheer number of ''Deinonychus'' teeth scattered throughout the formation are a testament to its abundance. ''[[Microvenator]]'', a small basal [[oviraptorosaur]], hunted smaller prey, while the [[apex predator]]s of the Cloverly were large [[allosauroid]] theropods. These beasts are known only from fragments, but may be related to the contemporaneous ''[[Acrocanthosaurus]]'' of Texas and Oklahoma to the south. [[Lungfish]], [[Triconodonta|triconodont]] [[mammal]]s and several species of [[turtle]]s lived in the Cloverly, while [[crocodilia]]ns prowled the rivers, lakes and swamps, providing evidence of a year-round warm [[climate]].<ref name=ostrom1970/><ref name=maxwell1997/> The [[Late Jurassic]] fauna dominated by allosauroids, [[stegosaur]]s and many varieties of huge [[sauropod]]s gave way by Cloverly times to an Early Cretaceous fauna in which dromaeosaurs, ornithopods, and nodosaurs like ''Sauropelta'' were predominant. After the Cloverly ended, a large wave of Asian animals, including [[tyrannosaurid]]s, [[ceratopsia]]ns and ankylosaurids would [[Biological dispersal|disperse]] into western North America, forming the mixed fauna seen throughout the [[Late Cretaceous]].<ref name=carpenterkirkland1998/>
==References==
{{reflist}}
==External links==
*Entries in [http://paleo.amnh.org/fossil/seek.html Online Collections Database] at the American Museum of Natural History:
**[http://paleo.amnh.org/fossil/show.html?cat_num=FR%203032 AMNH 3032] (pictures of assorted bones included)
**[http://paleo.amnh.org/fossil/show.html?cat_num=FR%203035 AMNH 3035] (pictures of skull and cervical armor included)
**[http://paleo.amnh.org/fossil/show.html?cat_num=FR%203036 AMNH 3036]
*Entry for [http://tolweb.org/Nodosauridae/15772 Nodosauridae] on [http://tolweb.org/tree/phylogeny.html Tree of Life], including modern restoration of ''Sauropelta'' armor
{{portalpar|Dinosaurs}}
[[Category:Ankylosaurs]]
[[Category:Cretaceous dinosaurs]]
[[Category:Dinosaurs of North America]]
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