Camarasaurus presented a distinctive cranial profile of a blunt snout and an arched skull that was remarkably square, typical of basal macronarians. The generic name means "chambered lizard", referring to the hollow chambers, known as pleurocoels, in its cervical vertebrae (GreekTemplate:Lang [[[:Template:Translit]]] meaning 'vaulted chamber', or anything with an arched cover, and Template:Lang [[[:Template:Translit]]] meaning 'lizard').
Camarasaurus contains four species that are commonly recognized as valid: C. grandis, C. lentus, C. lewisi, and C. supremus. C. supremus, the type species, is the largest and geologically youngest of the four. Camarasaurus is the type genus of Camarasauridae, which also includes its European close relative Lourinhasaurus. Camarasaurus was named in 1877 by Edward Drinker Cope, during the period of scientific rivalry between him and Othniel Charles Marsh known as the Bone Wars. Soon after, Marsh named a genus Morosaurus, but it was subsequently shown to be synonymous with Camarasaurus.
Fossils of Camarasaurus were first discovered in the spring of 1877 by Oramel William Lucas, a school superintendent, in Morrison Formation rocks in Garden Park, Colorado. These fossils were sent to Edward Drinker Cope, a paleontologist based in Philadelphia, who identified it as belonging to a new genus and species, which he named Camarasaurus supremus, meaning "chambered lizard, from the GreekTemplate:Lang (Template:Lang) meaning "vaulted chamber", or anything with an arched cover, and Template:Lang (Template:Lang) meaning "lizard"), and from the Latinsupremus, "supreme" or "highest".<ref name="gs">Template:Cite journal</ref><ref>Template:Cite journal</ref> By this time, the Morrison Formation had become the main battleground of the Bone Wars, a fossil-collecting competition between Cope and paleontologist Othniel Charles Marsh. Due to this, at the time many descriptions of taxa, such as that of Camarasaurus, were rushed by Cope and Marsh.<ref name="BMunpublished">Template:Cite journal</ref> Camarasaurus supremus' type specimen (AMNH 5760) consists of: one cervical vertebra, the namesake of the genus, two dorsal vertebrae, and three caudal vertebrae. However, these elements are from differing individuals, making them cotypes.<ref name="ca"/> The cervical vertebra has been proposed to be the lectotype of C. supremus, though there has not been a published stance.<ref name="tschopp2016" />
Between August 1877 and 1878, Lucas unearthed and sent many more C. supremus fossils, including: two cervicals, 18 dorsals, 55 caudals, 17 left ribs and several right ones, eight chevrons, one right scapula, one right coracoid, two pubes, four ischia, one femur, and one fibula. These elements came from the "Yellow Beds" of Garden Park and were also grouped with AMNH 5760, as Cope erroneously believed they belonged to the same individual.<ref name="gs"/><ref name="ca"/> Based on the fossils found at Garden Park, Cope erected several more genera and species of dinosaur including; Camarasaurus leptodirus (1877), Caulodon diversidens (1877), Caulodon leptoganus (1878), and Amphicoelias latus (1877). All of these species are considered synonyms of C. supremus and were described on the basis of fragmentary or isolated fossils.<ref name="ca"/><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> Many other taxa were named by Cope based on fossils from Garden Park, including Epanterias, Amphicoelias altus, and Hypsirhophus.<ref>McIntosh, J. S. (1998). New information about the Cope collection of sauropods from Garden Park, Colorado. Modern Geology, 23, 481.</ref><ref name="ca"/>
More fossils would be found throughout the late 1870s into 1880 by O. W. Lucas and his brother, Ira H. Lucas. All fossils found by I. H. Lucas were then separated into AMNH 5761, however this specimen too included several, jumbled skeletons from multiple individuals. The total number of specimens from Garden Park referred to C. supremus includes: one Template:Dinogloss, one Template:Dinogloss, one Template:Dinogloss, two Template:Dinogloss, several teeth, 23 cervicals, 38 dorsals, two sacra, 102 caudals, 25 chevrons, two sternal plates, 110 ribs, six scapulae, two coracoids, two humeri, two metacarpals, five ilia, eight ischia, six pubes, four femora, four tibiae, two fibulae, one Template:Dinogloss, and one metatarsal. However, the referral of some of these fossils is questionable, as many are fragmentary or may belong to other sauropods. Intermingled are the remains of possibly six or more individuals,<ref name="ikejiri2005" /><ref name="ca" /> some of which were found alongside bones of theropods and ornithischians.<ref name="carpenter1998" /> Later, these fossils were prepared and cleaned by Jacob Geismar under Cope's direction between 1877 and the 1890s. Many additional fossils were illustrated and described by Cope in 1878, but a full review of all the Garden Park dinosaur fossils was published by Henry Osborn and Charles C. Mook in 1921.<ref name="ca"/>
The earliest known skeletal reconstruction of a sauropod dinosaur: C. supremus by John A. Ryder, 1877
In 1877, Cope commissioned Dr. John A. Ryder to create a restoration of Camarasaurus using the known fossils of several individuals. Due to using multiple individuals, factors like the vertebral count and proportions were inaccurate. Additionally, Camarasaurus was known only from skull fragments at the time, leading to a largely hypothetical skull which bore carnivorous teeth. This reconstruction would be the first ever made of a sauropod dinosaur and was natural size, measuring over Template:Convert.<ref name="iw"/><ref name="ca"/>
Morosaurus
Between 1877 and 1879, paleontologists William Reed, Marshall P. Felch, and Samuel W. Williston found an incomplete, partially articulated skeleton (YPM 1901)<ref name=":3">Marsh, O. C. (1877). "Notice of New Dinosaurian Reptiles from the Jurassic Formation". American Journal of Science. 3rd series. 14 (84): 514–516. Bibcode:1877AmJS...14..514M. doi:10.2475/ajs.s3-14.84.514. S2CID 130488291.</ref> of a juvenile sauropod in Quarry 1 at Como Bluff, Wyoming. Marsh was sent part of the specimen which he described in 1877 as belonging to a new species of the genus Apatosaurus, naming it Apatosaurus grandis, the specific name coming from the Latin grandis meaning "great".<ref name=":3" /> This skeleton would be the best preserved single individual of Camarasaurus known at the time, consisting of: a Template:Dinogloss, several dorsals, a partial sacrum, the first 27 caudals, a complete left and incomplete right pectoral girdle, an incomplete left forelimb, femora, tibiae, fibulae, and ribs.<ref name="white1958" /><ref name="ikejiri2005" /> Additionally, several paratypes were unearthed from the same locality, including: an incomplete skull and partial postcranial skeleton (YPM 1905), the holotype sacrum of the later named Morosaurus impar (YPM 1900), and a fragmentary postcranial skeleton (YPM 1903).<ref>Template:Cite web</ref><ref name="ikejiri2005" /><ref name="white1958" /> In 1878, Williston sent Marsh an isolated juvenile sauropod sacrum (YPM 1900) he had found at Como Bluff alongside material of A. grandis. Marsh then described the sacrum as belonging to a new genus and species, Morosaurus impar, which he believed was related to Apatosaurus, Brontosaurus,<ref>Template:Cite journal</ref> and Atlantosaurus.<ref>Template:Cite journal</ref> Morosaurus' name comes from the Greek Μόρος (moros meaning "stupid"), in reference to its small brain size compared to its body size, and Template:Lang (Template:Lang meaning "lizard").<ref name=":20">Template:Cite web</ref> Marsh went on to refer five species of Morosaurus: M. impar, M. robustus, M. agilis, M. lentus, and M. grandis, which was previously named Apatosaurus grandis.<ref name="lj" /> M. lentus, the specific name coming from the Latin lentus meaning "slow", was named in 1889 by Marsh based on jaws and an incomplete skeleton that was also found at Como Bluff.<ref name="lj"/><ref>Template:Cite journal</ref> Its type specimen, YPM 1910, was mounted at the Yale Peabody Museum fossil hall in 1930 and was one of the first nearly complete sauropod skeletons to be found.<ref>Template:Cite journal</ref>
Following the Bone Wars, paleontologists also attempted to tackle the taxonomy of the many dinosaur genera named by Marsh and Cope.<ref name="ca"/><ref name="lj" /> In 1898, Williston synonymized M. impar with M grandis,<ref>Template:Cite journal</ref> a suggestion supported by later authors.<ref name="fl" /><ref name="ca" /><ref name=":2" /> In 1901, American researcher Elmer Riggs concluded that of the five Morosaurus species named at the time, only three were valid: M. grandis, M. lentus, and M. agilis.<ref name="op"/> Riggs synonymized M. impar, the type species, with M. grandis and further suggested that Morosaurus and Camarasaurus were synonyms.<ref name="fl">Template:Cite journal</ref> However, the suggestion that Morosaurus and Camarasaurus were generic synonyms was not formalized until later research.<ref name="lj" /> In their 1921 monograph on Camarasaurus, Osborn and Mook synonymized Morosaurus with Camarasaurus,<ref name="ca" /> an idea that has been accepted since.<ref name="white1958" /><ref name="gilmore1925" /> In 1925, American researcher Charles W. Gilmore mistakenly synonymized C. grandis with C. impar despite the former being named first.<ref name="gilmore1925" /> M. impar and M. robustus are now considered synonyms of C. grandis<ref name="ikejiri2005" /><ref name="lj" /> and M. agilis has since been moved to its own genus, Smitanosaurus.<ref name="lj"/>
Second dinosaur rush
After the end of the Bone Wars, many major institutions in the eastern United States were inspired by the depictions and finds by Marsh and Cope to assemble their own dinosaur fossil collections.<ref name="pb">Template:Cite book</ref>Template:Rp The competition to mount the first sauropod skeleton specifically was the most intense, with the American Museum of Natural History (AMNH), Carnegie Museum of Natural History (CM), and Field Museum of Natural History (FMNH) all sending expeditions to the west to find the most complete sauropod specimen,<ref name="pb"/>Template:Rp bring it back to the home institution, and mount it in their fossil halls.<ref name="pb" />Template:Rp In the mid-late 1890s, the AMNH and FMNH were the first to mount expeditions, finding sauropod material at Como Bluff and Fruita, Colorado respectively.<ref name="pb" />Template:Rp This material, mostly consisting of limb bones, was referred to Morosaurus and led to new reconstructions of sauropod manus and pes structure.<ref name=":2">Template:Cite journal</ref><ref name="fl"/> In the 1890s, Osborn also suggested that Morosaurus was a synonym of Camarasaurus.<ref name="ca"/><ref>Template:Cite journal</ref> In 1899, AMNH field workers Walter Granger and Peter Kaisen unearthed a complete Camarasaurus skull, mandible, and associated cervical vertebrae in rock layers at Bone Cabin Quarry, Wyoming, the first discovery of a nearly complete Camarasaurus skull.<ref>Template:Cite web</ref><ref name="sb">Template:Cite journal</ref> In 1905, a plaster skull based on the Camarasaurus skull found at Bone Cabin Quarry and based on a skull later referred to Brachiosaurus<ref name="D'Emic-2019">Template:Cite journal</ref><ref name="carpenter98">Template:Cite book</ref> was mounted on a skeleton of Brontosaurus,<ref name="camarasaurusbully">Template:Cite web</ref><ref name="sb"/> leading to a trend of mistakenly mounting Camarasaurus-like skulls on apatosaurine bodies. This was the first-ever mounted skeleton of a sauropod.<ref name="sb"/>
Around the same time as the AMNH, the CM was conducting its own fossil expeditions to quarries in Wyoming where it recovered several Camarasaurus specimens. However, paleontologists of the time assigned these fossils to Morosaurus instead of Camarasaurus.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> In 1909, American fossil hunter Earl Douglass of the CM uncovered an extensive deposit of dinosaur fossils at what is now the iconic Dinosaur National Monument near Jensen, Utah.<ref>Template:Cite journal</ref> In 1914 during excavations at the Monument, Douglass unearthed a nearly complete skull and skeleton of a juvenile C. lentus still preserved in articulation. In 1925, this skeleton was then described by Charles W. Gilmore who supported the claim that Morosaurus is a synonym of Camarasaurus, a position supported by other authors.<ref name="ikejiri2005" /><ref name="white1958" /> This skeleton is one of the best sauropod specimens known to science, with nearly every element preserved in articulation. Sometime prior to 1922, another Camarasaurus skeleton was found at Dinosaur National Monument by Douglass however it remained in a plaster jacket for many years. In an exchange for several fossils, money, and time to work with Gilmore, the National Museum of Natural History acquired the skeleton and several other fossils. This specimen was then prepared publicly at the Texas Centennial Exposition of 1936 before it was mounted in a death pose in the museum's fossil hall in 1947. This skeleton would turn out to be the second most complete skeleton of Camarasaurus known.<ref>Template:Cite web</ref><ref name="ikejiri2005" /> It too was referred to C. lentus by paleontologists.<ref name="white1958" /><ref name="ikejiri2005" />
In 1967, American researcher James Jensen collected a well preserved and articulated postcranial skeleton of Camarasaurus from Uncompahgre Hill in western Colorado which was then deposited at Brigham Young University under specimen number BYU 9740.<ref name="jm">McIntosh, J.S., Miller, W.E., Stadtman, K.L., and Gillette, D.D., 1996b, The osteology of Camarasaurus lewisi (Jensen, 1988): Brigham Young University Geology Studies, v. 41, p. 73-115.</ref><ref name="jj">Template:Cite journal</ref> This skeleton remained unprepared for many years and was not described until 1988, where Jensen described it as belonging to a new genus and species of sauropod, Cathetosaurus lewisi.<ref name="jj" /><ref name="jm" /><ref name="mm">Mateus, O., & Tschopp E. (2013). Cathetosaurus as a valid sauropod genus and comparisons with Camarasaurus. Journal of Vertebrate Paleontology, Program and Abstracts, 2013. 173.</ref> The generic name Cathetosaurus lewisi comes from the Greek κάθετος (kathetos meaning "vertical"), in reference to its supposed ability to stand upright, and Template:Lang (Template:Lang meaning "lizard"), and the species name is in honor of Arnold D. Lewis, a fossil preparator and field worker.<ref name=":20" /><ref name="jj" /> This original 1988 description was brief,<ref name="jj" /> but John McIntosh and colleagues extensively described BYU 9740 in 1996 where they determined that Cathetosaurus lewisi was a species of Camarasaurus,<ref name="jm" /> an opinion supported by many other authors.<ref name="ikejiri2005" /><ref name="kw" /><ref>Template:Cite journal</ref> In 2013, paleontologists Octavio Mateus and Emanuel Tschopp argued in a conference abstract that Cathetosaurus is a distinct genus,<ref name="mm" /> but this was not supported by later research and phylogenetic analyses (studies of the interrelationships of organisms).<ref name="tschopp2016" /><ref name="tschopp2019" /><ref name="kw">Wiersma, K., & Sander, P. M. (2017). The dentition of a well-preserved specimen of Camarasaurus sp.: implications for function, tooth replacement, soft part reconstruction, and food intake.PalZ, 91(1), 145-161.</ref>
In 1992, a nearly complete and articulated skeleton of C. grandisTemplate:Sfn was collected by fossil hunter Jeffrie Parker and colleagues from a site near the Bone Cabin Quarry.Template:Sfn This specimen now resides at the Gunma Museum of Natural History in Tokyo, Japan under specimen number GMNH-PV 101.<ref name="ikejiri2005" />Template:Sfn Another well-preserved Camarasaurus specimen was found in 1992 at the Howe Quarry in Wyoming by Swiss field workers working for the Sauriermuseum Aathal in Zurich, Switzerland. The skeleton is one of the best known, with nearly every element articulated and skin impressions from the skull and hindlimb.<ref>Template:Cite web</ref><ref name="kw" /> The specimen, SMA 002, has not yet gotten a full identification, but has been suggested to be a specimen of C. lewisi.<ref name="kw" /> In 1996, several fragmentary remains of Camarasaurus were described from western South Dakota<ref>Foster, J. R. (1996). Sauropod dinosaurs of the Morrison Formation (Upper Jurassic), Black Hills, South Dakota and Wyoming.Rocky Mountain Geology, 31(1), 1-25.</ref> and New Mexico,<ref name="sl">Template:Cite journal</ref> extending the northeastern and southern range of the genus. The New Mexican remains were found in the Summerville Formation, indicating Camarasaurus lived outside of the Morrison Formation.<ref name="sl" /> In 2005, the northernmost specimen, an incomplete skull and postcranial skeleton, of Camarasaurus was discovered in the Little Snowy Mountains of Montana.Template:Sfn
Fossil record
Camarasaurus fossils are very common.<ref name="foster2020" /> Over 500 specimens are known, including many isolated bones and about 50 partial skeletons.Template:Sfn It is found in a wide area over the western United States, from as far north as Montana to as far south as New Mexico, in rocks of the Morrison Formation.Template:Sfn Due to this abundance, Camarasaurus is a very well-known sauropod. A juvenile specimen of Camarasaurus, CM 11338, is the most complete sauropod skeleton ever discovered. Numerous skulls are known.Template:Sfn Even though complete necks are rarely found in sauropods, five specimens of Camarasaurus preserve all or nearly all of the cervical vertebrae.Template:Sfn Most identifiable specimens of Camarasaurus belong to one of two species, C. grandis and C. lentus; C. lewisi and C. supremus are rarer.Template:Sfn
Description
Scale diagram of three known species of Camarasaurus
As a sauropod, Camarasaurus had an elephant-like body with a long neck ending in a proportionately small skull, and extremely lightly build vertebrae of the trunk and neck that were in stark contrast to the massive, columnar limbs.<ref name="sander2010">Template:Cite journal</ref>Template:Rp Compared to other sauropods, it was relatively bulky with a wide belly. The neck and tail were comparatively short and the skull large. Due to its relatively long forelimbs, it was slightly taller at the shoulders than at the hips.<ref name="foster2020" /><ref name="paul2024" />
Camarasaurus was a medium to large-sized sauropod.<ref name="ikejiri2005"/><ref name="foster2020" /> The most common species, C. lentus, was about Template:Cvt in length, and C. grandis and probably C. lewisi were comparable in size.<ref name="Benton, Michael J, Prehistoric Life">Template:Cite book</ref><ref name="foster2020" /> The body weight of adult C. grandis has been estimated to be about 12.6 tonnes on average, ranging from 8.3 tonnes in the smallest to 16.6 tonnes in the largest specimen.<ref name="foster2020" /> In 2020, John Foster stated that the latest species, C. supremus, had bones about 50% longer than those of the smaller species.<ref name="foster2020" /> Although C. supremus is too incompletely known to allow for precise size estimates, it would have reached almost Template:Cvt in length and 42.3 tonnes in weight if its body proportions were identical to those of the smaller species.<ref name="foster2020" /> American paleontologist Gregory S. Paul, in 2024, instead gave a length estimate of Template:Cvt and a weight estimate of 24 tonnes for this species.<ref name="paul2024">Template:Cite book</ref>
Skull
C. supremus skull
The skull was larger and more strongly build than in other sauropods, with massive upper and lower jaws.<ref name="christiansen2000" /><ref name="ikejiri2005"/><ref name="foster2020" /> As in the contemporary Brachiosaurus, the Template:Dinogloss (nostril) was enlarged, resulting in an arched forehead.<ref name="upchurch2004">Template:Cite book</ref><ref name="gilmore1925" />Template:Rp Both genera had a well-defined snout,<ref name="wilson2012">Template:Cite book</ref> but the skull of Camarasaurus was more rounded and short-faced.<ref name="foster2020" /><ref name="mcintosh1975">Template:Cite journal</ref>Template:Rp When viewed from above, the snout was rounded and slightly tapering, different to the rectangular snout of Diplodocus. The skull was almost rectangular when viewed from the back and higher than wide.<ref name="gilmore1925" />Template:Rp
The largest openings that penetrated the skull were the external naris, the Template:Dinogloss (eye opening), and the Template:Dinogloss, which was located behind and below the orbit. These three openings were about the same size. The external naris was oval in shape, and the orbit was teardrop-shaped, tapering to a point at its lower end. The orbit contained a sclerotic ring, a ring of small plate-like bones around the pupil of the eye. The infratemporal fenestra was roughly triangular and tilted backwards at an angle of 30°. A small and pear-shaped Template:Dinogloss was present between the external naris and the orbit. Even smaller was the Template:Dinogloss, which was present in the rear corners of the skull roof and mostly facing upwards. This opening was oval in shape and obliquely oriented.<ref name="madsen1995">Template:Cite journal</ref>Template:Rp<ref name="gilmore1925" />Template:Rp<ref name="christiansen2000" />
The skull showed several autapomorphies (features not found in related genera). According to a 2004 review, these include the Template:Dinogloss (the bone that formed the front margin of the orbit), which was tilted forwards. The Template:Dinogloss, a columnar bone at the rear of the skull, did not reach the infratemporal fenestra as its upwards-facing part was short. The Template:Dinogloss, which formed the rear-bottom corner of the skull, reached upwards to make contact with the Template:Dinogloss. The side surface of the lower jaw had an oblique groove running from the surangular bone forwards and downwards to the lower margin of the Template:Dinogloss.<ref name="upchurch2004" />Template:Rp
Known specimens had four teeth in each Template:Dinogloss (the front bone of the upper jaw), 9 to 10 teeth in each Template:Dinogloss (the main bone of the upper jaw), and 13 teeth in each lower jaw.<ref name="madsen1995" /> The teeth were spoon-shaped and formed a continuous cutting edge. The teeth increased in length, and became more symmetric, towards the tip of the snout. The teeth were tilted forwards and bent slightly inwards. The front edges of the teeth were more curved than the rear edges, and the teeth in the lower jaw were straighter and slightly less robust than those of the upper jaw. This makes it possible to determine whether an isolated tooth came from the left or right side of the jaw and whether it came from the upper or lower jaw.<ref name="white1958">Template:Cite journal</ref>Template:Rp<ref name="gilmore1925" />Template:Rp<ref name="wiersma2017" />
Postcranium
Restoration of a C. supremus herd
The vertebral column consisted of 12 cervical (neck), 12 dorsal (back), and five sacral (hip) vertebrae.<ref name="foster2020" /><ref name="mcintosh1996" />Template:Rp The tail was composed of 53 caudal vertebrae in the complete skeleton CM 11338, but the exact count might have varied between individuals.<ref name="mcintosh1996" />Template:Rp Most of the volume of the dorsal and cervical vertebrae was made up by air sacs which were connected to the lungs. These air sacs filled extensive excavations in the vertebrae that gave Camarasaurus its name (Template:Gloss).<ref name="taylor2013" />Template:Rp<ref name="creisler" /> The cervical and dorsal vertebrae were Template:Dinogloss (concave at the rear and convex at the front) and had large excavations on their sides called Template:Dinogloss.<ref name="gilmore1925" />Template:Rp<ref name="mcintosh1996" />Template:Rp The Template:Dinogloss (the top parts of the vertebrae) of the shoulder region were split, and the left and right halves formed a U-shape when viewed from the front or back. In the hip region, the neural spines were not split, short, and fan-shaped when viewed from the front or back.<ref name="foster2020" /><ref name="madsen1995" />Template:Rp The neural spines of the second to fifth sacral were often fused together.<ref name="madsen1995" />Template:Rp The cervical vertebrae had very slender and elongated Template:Dinogloss that overlapped multiple preceding vertebrae.<ref name="gilmore1925" />Template:Rp<ref name="foster2020" />
The left and right halves of the shoulder girdle were probably connected at the front of the trunk by the Template:Dinogloss.<ref name="schwarz2007" />Template:Rp The upper end of the shoulder blade was expanded. In the hip, the pubis was massive, while the shaft of the ischium was slender, curved, and its end was not expanded. The articulation surface between the pubis and ischium was long.<ref name="foster2020" /><ref name="madsen1995" />Template:Rp The forelimb was slender, and the Template:Dinogloss was about 77% the length of the Template:Dinogloss (upper thigh bone). In contrast, the hindlimb was massive, and the Template:Dinogloss (shin bone) was about 60% the length of the femur. Camarasaurus is one of few sauropods that preserve the wrist, which in this genus consisted of only two bones, the Template:Dinogloss and the Template:Dinogloss.<ref name="ikejiri2005" /><ref name="upchurch2004" />Template:Rp As in other macronarians, the five metacarpals were long, with the third metacarpal reaching one third of the length of the humerus.<ref name="madsen1995" />Template:Rp<ref name="upchurch2004" />Template:Rp As typical for sauropods, the metacarpals were vertical and arranged in a tube-like fashion. The fingers were strongly reduced, with the thumb consisting of two Template:Dinogloss (finger bones), including a claw that was slanted sidewards. The remaining digits possibly consisted of one phalanx, and lacked claws.<ref name="gilmore1925" />Template:Rp<ref name="upchurch2004" />Template:Rp In the ankle of the hind foot, the Template:Dinogloss was small and rounded.<ref name="madsen1995" />Template:Rp As in other sauropods, the hind foot had five digits, consisting of 2, 3, 4, 2, and 1 phalanx, respectively. The first three toes had recurved claws that were strongly flattened side-to-side.<ref name="upchurch2004" />Template:Rp
Classification and species
Camarasauridae
Camarasaurus is the type genus of the family Camarasauridae, a clade that is typically regarded as only including Camarasaurus itself. However, phylogenetic analyses have recovered genera like Bellusaurus, Tehuelchesaurus, and Lourinhasaurus as members of the family.<ref name=":0" /><ref name=":1" /><ref name="op" /> Cope recognized that Camarasaurus was a relative of Cetiosaurus, Bothriospondylus, Ornithopsis, and Anchisaurus (Megadactylus) in his description, but failed to name a family for these taxa.<ref>Cope, E.D., 1877a, On a gigantic saurian from the Dakota Epoch of Colorado: Paleontological Bulletin, v. 25, p. 5-10.</ref> In 1878 with the description of Amphicoelias, Cope named the families Camarasauridae and Amphicoelidae based on differences in vertebral anatomy, however he did not specify what other taxa were members of these groups.<ref>Template:Cite journal</ref>
In 1970, Rodney Steel took an expansive concept of Camarasauridae, encompassing all sauropods then known except diplodocoids and titanosaurs.<ref>Steel, Rodney (1970). Saurischia. Handbuch der Paläoherpetologie. Stuttgart: Gustav Fischer Verlag.</ref> In 1990, John S. McIntosh regarded Camarasauridae as made up of two subfamilies: Camarasaurinae, containing Camarasaurus, Aragosaurus, Euhelopus, and Tienshanosaurus, and Opisthocoelicaudiinae, containing Opisthocoelicaudia and Chondrosteosaurus.<ref name="iw"/> Dashanpusaurus, from the Middle Jurassic of China, was originally described as a camarasaurid, but was subsequently found to be a basal macronarian by phylogenetic analysis.<ref>Template:Cite journal</ref> Many of these taxa were referred to Camarasauridae in the 20th century on the basis of their teeth anatomy, such as Euhelopus, Asiatosaurus, and Chiayusaurus, or vertebral anatomy, like Opisthocoelicaudia, but are now thought to be in different groups. Camarasauridae is often seen as monophyletic, but a wider group known as Camarasauromorpha has been recovered in phylogenetic analyses.<ref name="op"/><ref>Template:Cite journal</ref> This group was initially defined as applying to the clade including the most recent common ancestor of Camarasauridae and Titanosauriformes and all of its descendants.<ref>Template:Cite journal</ref>
Several sauropods have been suggested to be in Camarasauridae, or in a wider group known as Camarasauromorpha, including Lourinhasaurus, Bellusaurus, and Oplosaurus, however this has come under critiscism.<ref>Template:Cite journal</ref><ref name=":1" /><ref name="tschopp2016" /> Bellusaurus was recovered as a Camarasaurid in a 2014 paper, but has been considered a member of Turiasauria,<ref name="ta"/> Mamenchisauridae,<ref>Template:Cite journal</ref> or basal Macronaria.<ref name=":1">Template:Cite journal</ref> Lourinhasaurus was classified as a camarasaurid and a species of Camarasaurus itself, but some studies have found it to be a basal neosauropod,<ref>Template:Cite journal</ref> basal macronarian<ref name=":0">Template:Cite journal</ref> or eusauropod,<ref>Template:Cite journal</ref><ref>Upchurch, Paul; Barrett, Paul M.; Dodson, Peter (2004). "Sauropoda". In Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.). The Dinosauria (2 ed.). Berkeley: University of California Press. pp. 259–322. Template:ISBN.</ref> or laurasiform instead.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> However, in a 2019 study, Mannion and colleagues found Lourinhasaurus as a sister taxon of Camarasaurus.<ref name="ta">Template:Cite journal</ref> The dubious British genus Oplosaurus has been suggested to be a camarasaurid,<ref>Template:Cite journal</ref> however other studies have placed it in Turiasauria<ref>Template:Cite journal</ref><ref>Template:Cite web</ref> or Macronaria in general.<ref>Template:Cite journal</ref>
Camarasaurus is regarded as containing four valid species by most researchers: C. grandis, C. lentus, C. lewisi, and C. supremus.<ref name="tschopp2019" /> C. supremus, the species named by Cope in 1877, is the type species. C. grandis was named in 1877 and C. lentus in 1889. The fourth species, C. lewisi, is of uncertain affinities. It was originally described as a distinct genus, Cathetosaurus, in 1988, but reclassified as a species of Camarasaurus in 1996.<ref name="jensen1988" /><ref name="mcintosh1996a" /> Some researchers have suggested that Cathetosaurus should be reinstated as a distinct genus,<ref name="mm"/><ref name="tschopp2014" /><ref name="tschopp2019" /> whereas others have suggested that C. lewisi may be synonymous with another Camarasaurus species.<ref name="ikejiri2005" />Template:Sfn
Stratigraphic evidence suggests that chronological sequence aligned with the physical differences between the three species, and it describes an evolutionary progression within the Morrison Formation. C. grandis is the oldest species and occurred in the lowest rock layers of the Morrison. C. lewisi only briefly coexisted with C. grandis in the lowest strata of the upper Morrison until going extinct,<ref name="ikejiri2005" /> but it is possible this is because of a lack of specimens from C. lewisi.<ref name="ikejiri2005" /> C. lentus appeared later, co-existing with C. grandis for several million years, possibly due to different ecological niches as suggested by differences in the spinal anatomy of the two species. At a later stage, C. grandis disappeared from the rock record, leaving only C. lentus.<ref name="ikejiri2005" /> Then C. lentus, too, disappeared; at the same time, C. supremus appeared in the uppermost layers. This immediate succession of species, as well as the very close similarity between the two, suggests that C. supremus may have evolved directly from C. lentus, representing a larger, later-surviving population of animals.<ref name="foster-cgrandis">"Camarasaurus grandis," Foster (2007). Page 204.</ref>
Synonyms
Amphicoelias latus was named in 1877 by Cope in the same paper that described A. altus. It was described on the basis of a right femur and four caudal vertebrae that had been found at Garden Park alongside fossils of C. supremus. However, it is now considered a synonym of C. supremus or C. grandis.<ref name="carpenter1998" /><ref name="ikejiri2005" />
Caulodon diversidens was named in 1877 by Cope on the basis of several teeth. These teeth however are undiagnostic and have been considered either indeterminate macronarian or synonym of C. supremus.<ref name="ikejiri2005" /><ref name="ca">Template:Cite web</ref>
Caulodon leptoganus was named in 1878 by Cope on the basis of two incomplete teeth. These teeth are undiagnostic and have been considered either indeterminate macronarian or synonym of C. supremus.<ref name="ikejiri2005" /><ref name="ca" />
Morosaurus impar was named in 1878 by Marsh as the type species of his genus Morosaurus. This species was named on the basis of a sacrum that had been found at Como Bluff. However, it is now considered a synonym of C. grandis.<ref name="ikejiri2005" />
Morosaurus robustus was named in 1878 by Marsh on the basis of an ilium that had been collected at Como Bluff. It is now considered a synonym of C. grandis.<ref name="ikejiri2005" />
Camarasaurus leptodirus was in 1879 by Cope on the basis 3 partial cervical vertebrae. It has been suggested to be a synonym of C. supremus.<ref name="ikejiri2005" />
Diplodocus lacustris was named in 1884 by Marsh on the basis of several teeth, a premaxilla, and a maxilla. These fossils were collected by American fossil hunters Arthur Lakes and Benjamin Mudge in 1877 from an outcrop in Morrison, Colorado.<ref name="as">Template:Cite journal</ref> However, this species has been considered a chimera. Although the teeth and dentary of D. lacustris are flagellicaudatan, the skull material is likely from a Camarasaurus.<ref name="as" />
Pleurocoelus montanus was named in 1896 by Marsh as a new species of Pleurocoelus on the basis of several vertebral centra and assorted bones of a juvenile sauropod found at Como Bluff. It is generally regarded as a synonym of C. grandis.<ref name="ikejiri2005" /><ref name="cp">Template:Cite web</ref>
Uintasaurus douglassi was named in 1919 by American paleontologist W. J. Holland for 5 anterior cervical vertebrae unearthed from Dinosaur National Monument.<ref name="holland1924">Holland, W. J. (1924). "Description of the Type of Uintasaurus douglassi HOLLAND". Annals of the Carnegie Museum. 15 (2–3): 119–138.</ref> The species was later regarded as a synonym of C. lentus.<ref name="ikejiri2005" /><ref name="white1958" />
Camarasaurus annae was named in 1950 by American zoologist Tage Ellinger on the basis of an isolated dorsal vertebra that had been found at Dinosaur National Monument.<ref>Template:Cite journal</ref> This species is generally considered a synonym of C.lentus.<ref name="ikejiri2005" />File:CaulodonTeethType.pngTeeth from the Caulodon diversidens holotype.
Reassigned species/specimen
Morosaurus agilis was named in 1889 by Marsh on the basis on a partial skull and 3 vertebrae unearthed in Garden Park, Colorado.<ref>O. C. Marsh. 1889. Notice of new American Dinosauria. The American Journal of Science and Arts, series 3 38:331-336</ref> The species remained in taxonomic uncertainty until 2020, when it was placed in a new genus, Smitanosaurus, and reclassified as a dicraeosaurid.<ref name="lj">Template:Cite journal</ref>
Morosaurus marchei was named in 1898 by French scientist Henri Sauvage on the basis of an incomplete distal caudal vertebra and tooth found in the Upper Jurassic-aged Alcobaca Formation of Lisbon, Portugal.<ref>Sauvage, H. E. (1898). Vertébrés fossiles du Portugal: contributions à l'étude des poissons et des reptiles du jurassique et du crétacique. l'Académie royale des Sciences.</ref> He selected the caudal vertebra to be the holotype. Later, French paleontologists Albert de Lapparent & Georges Zbyszewski referred the holotype<ref name="olshevsky1991">Template:Cite journal</ref> vertebra to Megalosaurus insignis, whereas American paleontologist James Henry Madsen and colleagues assigned it to indeterminate Megalosauria.<ref name="madsen1995" /> The tooth was identified as belonging to an indeterminate turiasaurian in 2017.<ref>Mocho, P., Royo-Torres, R., Escaso, F., Malafaia, E., de Miguel Chaves, C., Narvaez, I., ... & Ortega, F. (2017). Upper Jurassic sauropod record in the Lusitanian Basin (Portugal): Geographical and lithostratigraphical distribution. Palaeontologia Electronica, 20(2).</ref>
Camarasaurus alenquerensis was named as a species of Apatosaurus in 1957 by Lapparent and Zbyweski on the basis of a partial postcranial skeleton from the Upper Jurassic-aged rocks of the Lourinha Formation in Lourinha, Portugal.<ref name="lz">A.F. de Lapparent & G. Zbyszewski, 1951, "Découverte d'une riche faune de Reptiles Dinosauriens dans le Jurassique supérieur du Portugal", Comptes Rendus de l'Académie des Sciences à Paris233: 1125-1127</ref> It was placed in Camarasaurus by American researcher John McIntosh in 1990,<ref name="iw">McIntosh, J.S. 1990. Sauropoda. In Weishampel, D.B.; Dodson, P.; & Osmólska, H. (eds.): The Dinosauria. Berkeley (University of California Press): 345-401</ref> but was granted a new genus in 1998, Lourinhasaurus.<ref name=":0" />
Paleobiology
Feeding
Camarasaurus was a herbivore that probably fed at moderate heights of Template:Cvt.<ref name="foster2020" />Template:Rp It might have been able to rear on its hind legs to reach higher vegetation, as indicated by anatomical features such as the short neural spines of its caudal vertebrae.<ref name="hallett2016" /> In 1998, Anthony Fiorillo analysed microscopic pits and scratches on the tooth surfaces and concluded that adult Camarasaurus consumed coarser foods than the contemporary Diplodocus. Juvenile Camarasaurus, in contrast, appeared to have consumed the same soft foods as adult Diplodocus.<ref name="fiorillo1998" /> Modern herbivorous mammals with rounded snouts are often selective feeders that feed on particular plants that are less abundant but nutritious, while wide-snouted species are non-selective feeders that feed on less nutritious but abundant food in bulk. Based on this observation, John Whitlock argued in 2011 that the round-snouted Camarasaurus and Brachiosaurus were selective feeders while the square-snouted diplodocids and rebbachisaurids were bulk feeders.<ref name="whitlock2011" /><ref name="hallett2016" /> The diet of adult Camarasaurus might have consisted of the leaves of conifers, such as those of the extinct Cheirolepidiaceae, and ginkgos.<ref name="hallett2016" /> In 2016, Mark Hallett and Matt Wedel suggested that female cones of araucarians as well as resins could have supplemented its diet.<ref name="hallett2016" />
File:Camarasaurus masticatory muscles.pngJaw adductor musculature (muscles responsible for closing the mouth) of Camarasaurus lentus. Origin and insertion surfaces for the muscles (left) and reconstructed muscles (right)
Camarasaurus probably had a more powerful bite than other sauropods due to the very large Template:Dinogloss (an upwards facing projection of the mandible) and the supratemporal fenestra that provided extensive attachement surfaces for large masticatory muscles (the external mandibular adductor muscles).<ref name="christiansen2000" /> A 2016 study by David Button and colleagues estimated that the bite force of Camarasaurus was almost four times higher than that of Diplodocus. The bite force was highest in the posterior portion of the tooth row, where it is estimated to have reached up to 1978 newton.<ref name="button2016" />Template:Rp<ref name="nabavizadeh2023" />Template:Rp The sturdy construction of the skull also suggests that it was able to resist greater stresses during feeding than other sauropods.<ref name="christiansen2000" /><ref name="button2016" /> Per Christiansen, in a 2000 paper, suggested that Camarasaurus was adapted to biting off vegetation, but did not rake leaves as Diplodocus or Brachiosaurus did.<ref name="christiansen2000" /> The upper and lower teeth appeared to have fit into each other. In a 1994 study, Jorge Calvo suggested that Camarasaurus could crush food items against its teeth by moving its jaws back and forth, allowing some degree of food processing before shallowing.<ref name="calvo1994" /><ref name="christiansen2000" />
As other dinosaurs, Camarasaurus continuously replaced its teeth, and underneath each erupted tooth there were up to three replacement teeth. A tooth was replaced after 62 days on average, as indicated by daily growth rings called von Ebner lines that are visible in cross-section of the teeth. This was slower than in Diplodocus, where a tooth only lasted for about 35 days, but as fast or faster than in ornithischian dinosaurs.<ref name="demic2013" /> In a 2017 study, Kayleigh Wiersma and Martin Sander described a patch of soft tissue covering parts of the lower jaw and teeth of a Camarasaurus specimen nicknamed "E.T.". This impression appears to have been the animal's gums, indicating that the tooth crowns were partly enclosed by gums. Such gums may explain why sauropod tooth rows are often found intact even when isolated from the jaws. These authors also suggested that the gums could have been covered by a hornybeak, which could have helped with cutting vegetation while protecting the teeth. The presence of such a beak is consistent with the presence of small foramina (openings) and grooves on the outer surfaces of the jaws that would have contained blood vessels in life.<ref name="wiersma2017" /> Alternatively, these blood vessels could have supported "lips" like those found in today's lizards.<ref name="nabavizadeh2023" />Template:Rp
A juvenile and heavily scavenged Camarasaurus specimen from Wyoming was found with 14 polished quartz stones that are between Template:Cvt in diameter and have been identified as gastroliths (stomach stones). Sauropods were once assumed to have swallowed such stones to help grind food in the stomach, but the rarity of skeletons preserving gastroliths and their low numbers suggest that they were instead swallowed accidentally or for mineral intake.<ref name="wings2015" /><ref name="sander2010" />Template:Rp
Neck posture and function
Template:Main
The long necks of sauropods might have evolved for feeding on plants that were high above the ground or otherwise difficult to access, or to maximize the amount of food they could access without moving the body, thus saving energy.<ref name="sander2010" />Template:Rp The probable neck posture has been the subject of controversy.<ref name="sander2010" />Template:Rp A 1921 skeletal reconstruction of Camarasaurus by Osborn and Mook shows a rather straight and horizontal neck,<ref name="stevens2005" />Template:Rp while some later authors assumed a nearly vertical, swan-like neck.<ref name="stevens2005" /><ref name="sander2010" />Template:Rp Some complete skeletons, such as the juvenile C. lentus specimen CM 11338, also show a vertical neck, but these represent opisthotonic death poses that do not necessarily reflect the original neck posture.<ref name="stevens2005" /> In 1998, John Martin and colleagues instead argued that the necks of sauropods were held approximately horizontal, like a beam. They stated that the neck of Camarasaurus would have been powerful and inflexible, and that the elongated cervical ribs would have braced it along its underside.<ref name="martin1998" /> In 1999 and 2005, Kent Stevens and Michael Parrish analyzed how the neck vertebrae connected to each other in neutral pose, and concluded that the necks of Camarasaurus and other sauropods were typically held straight with a slight downwards slope.<ref name="stevens1999" /><ref name="stevens2005" />Template:Rp
The idea of a more-or-less horizontal neck was questioned by several subsequent studies.<ref name="sander2010" />Template:Rp In 2005, David Berman and Bruce Rothschild used Computed tomography (CT) data to propose that there were two types of sauropod neck vertebrae, a robust type and a slender type. Camarasaurus had the robust type, indicating that its neck was held vertical or almost vertical, while the slender type suggests a horizontal neck posture.<ref name="berman2005" /> In 2009, Mike Taylor and colleagues showed that in modern animals, necks are usually extended and therefore curved upwards, suggesting that the same was true for sauropods. In a 2007 study, Paul Sereno and colleagues suggested that the head of Camarasaurus was habitually inclined downwards by about 15°, based on the orientation of the semicircular canals in the inner ear, which housed the sense of balance. Taylor and colleagues argued that in this posture, the occipital condyle would have faced downwards, requiring that the front part of the neck was steep, and possibly close to vertical.<ref name="taylor2009" /><ref name="sereno2007" />
The right shoulder blade of the specimen CM 11338 is inclined by approximately 45° with respect to the horizontal. Gilmore, in his 1925 monograph, argued that this specimen reflected the original orientation of the bone, and consequently, his skeletal reconstruction was slightly taller at the hips than at the shoulders. This finding contradicted the 1921 reconstruction of Osborn and Mook, which showed a much steeper shoulder blade, resulting in an animal that was taller at the shoulders than at the hips and with the base of the neck higher above the ground. Gilmore's interpretation of a low-angled shoulder blade subsequently became widely accepted for sauropods in general. In a 2007 study, Daniela Schwarz and colleagues compared the anatomy of the shoulder girdle with that of modern animals and concluded that Osborn and Mook's original interpretation of a steeply inclined (60–65°) shoulder blade and a consequently higher shoulder was correct.<ref name="schwarz2007" /> Ligaments would have run along the top of the neck, which would have been taut when the neck was sloping downwards or sidewards, helping with holding it. In a 2004 study, Takanobu Tsuihiji reconstructed the ligaments of Camarasaurus based on those Greater Rhea, in which the neural spines are similarly bifurcated. The nuchal ligament would have run along the top with branches connecting to either side of the bifurcated neural spines, while a second ligament, the Ligamentum elasticum interspinale, would have run in-between the two prongs of the bifurcated neural spines.<ref name="tsuihiji2004" /><ref name="nabavizadeh2023" />Template:Rp
Sexual dimorphism
In a 1991 study, Bruce Rothschild and David Berman noted that in 25% of Camarasaurus specimens, some of the foremost tail vertebrae were fused together. In Apatosaurus and Diplodocus, such fusion even occurred in 50% of the individuals. The fusion is caused by Template:Dinogloss rather than direct fusion of the vertebral bodies, suggesting that it was an adaptation for stiffening the tail. Rothschild and Berman argued that the fusion was a sexually dimorphic feature that occurred only in the males or only in the females. In males, it could have supported whip-lash motions with the tip of the tail during fights with other males. In females, the stiffening could have helped with arching the tail to allow for copulation.<ref name="rothschild1991" /> In a 2008 study, Takehito Ikejiri suggested that Camarasaurus specimens can be classified either as robust (strongly built) or as gracile (slender). These robust and gracile morphs also subtly differ in size and are apparent in the three most common species. Ikejiri argued that the two morphs reflect differences between the sexes, although it is unclear which morph represents male and which represents female individuals.<ref name="ikejiri2008" />
Long-bone histology enables researchers to estimate the age that a specific individual reached. A study by Griebeler et al. (2013) examined long-bone histological data and concluded that the Camarasaurus sp. CM 36664 weighed Template:Convert, reached sexual maturity at 20 years and died at age 26.<ref>Template:Cite journal</ref> A 2024 study estimated the maximum age at death for Camarasaurus sp. GPDM 220 to be around 35 years.<ref>Template:Cite journal</ref>
Metabolism
Eagle et al. performed clumped isotope thermometry on the enamel covering the teeth of various Jurassic sauropods, including Camarasaurus. Temperatures of Template:Convert were obtained, which is comparable to that of modern mammals.<ref name="eagle2011">Template:Cite journal</ref> Camarasaurus grew in size quickly to limit the time it would be vulnerable to predation. This would imply it had a relatively high metabolic rate as a juvenile.<ref>Template:Cite journal</ref>
Paleopathology
Template:Main
A Camarasaurus pelvis recovered from Dinosaur National Monument in Utah shows gouging attributed to Allosaurus<ref name="ageofdinosaurscamarasaurus" /> and on the ilium of the C. lewisi type there are large Theropod bite marks.<ref name="ford">Template:Cite web</ref>
In 1992, a partial C. grandis skeleton was discovered at the Bryan Small Stegosaurus Quarry of the Morrison Formation near Cañon City, Colorado.Template:Sfn This specimen preserved a partial right humerus cataloged as DMNH 2908 and associated vertebrae from the back and tail.Template:Sfn In 2001, Lorie McWhinney, Kenneth Carpenter, and Bruce Rothschild published a description of a pathology observed on the humerus.Template:Sfn They noted a juxtacortical lesion 25 by 18 cm wide made of bone that resembled woven fibers.Template:Sfn Although woven bone forms in accessory dental bone, in other locations, it is a sign of injury or illness.Template:Sfn The woven bone's "undulating fibrous bundles" were observed oriented in the direction of the m. brachialis.Template:Sfn The lesion's fusion and lack of porosity at its near and far ends indicate the periostitis was inactive or healed.Template:Sfn McWhinney and the other researchers argued that this injury would have been a continuous source of hardship for the animal.Template:Sfn It would have exerted pressure on the muscles.Template:Sfn This pressure would have compressed the muscles' blood vessels and nerves, reducing the range of motion of both the limb's flexor and extensor muscles.Template:Sfn This effect would have hindered the M. brachialis, m. brachoradialis, and to a lesser degree the m. biceps brachii to the lesion's position on the humerus.Template:Sfn The researchers inferred that the inflammation of the muscles and periosteum would have caused additional complications in the lower region of the fore limb, as well.Template:Sfn The lesion would also have caused long-term fasciitis and myosistis.Template:Sfn The cumulative effect of these pathological processes would have moderate to severe effects on the ability of the limb to move and "made everyday activities such as foraging for food and escaping predators harder to accomplish."Template:Sfn To help determine the cause of the pathology, McWhinney and the other researchers performed a CT scan in 3-mm increments.Template:Sfn The CT scan found that the mass had a consistent radiodensity and was separated from the cortex of the bone by a radiolucent line.Template:Sfn No evidence was found of stress fracture or infectious processes like osteomyelitis or infectious periostitis.Template:Sfn They also ruled out osteochondroma because the axis of the spur is 25° relative to the vertical axis of the humerus, whereas an osteochondroma would have formed at 90° to the axis of the humerus.Template:Sfn Other candidates identified by the scientists for the origin of the spur-bearing lesion included:
Avulsion injury – McWhinney and the other researchers considered an avulsion injury caused by "repetitive overexertion of the muscles" to be the most likely source for the lesion on the humerus.Template:Sfn The researchers believed the lesion to have originated with the avulsion of the m. brachialis causing the formation of "a downward-sloping elliptical mass".Template:Sfn The bone spur was caused by an osteoblastic response following a tear at the base of the m. brachioradialis caused by its flexor motion.Template:Sfn
The Morrison Formation, situated along the eastern flank of the Rocky Mountains, is home to a fossil-rich stretch of Late Jurassic rock. A large number of dinosaur species can be found here, including relatives of Camarasaurus such as Diplodocus, Apatosaurus, and Brachiosaurus, but camarasaurs are the most abundant of the dinosaurs in the formation.<ref name="foster-csupremus-abundance">"Camarasaurus supremus," Foster (2007). Page 201. "Abundances and Diversities," ibid. Page 248.</ref> Camarasaurus fossils have been found in almost every major locality and have one of the greatest known distributions of Morrison dinosaurs, with fossils found in localities from New Mexico to Montana and Utah to Oklahoma.<ref name="ikejiri2005" /> According to radiometric dating, the Morrison sedimentary layers range between 156.3 million years ago (Mya) at the base, to 146.8 Mya at the top, which places it in the late Oxfordian, Kimmeridgian, and early Tithonianstages of the Late Jurassic period.<ref name="trujillo2006">Template:Cite journal</ref><ref name="bilbey1998">Template:Cite book</ref> Its environment is interpreted as semiarid with distinct wet and dry seasons.
Dinosaur and trace fossils are found particularly in the Morrison Basin, which stretches from New Mexico to Alberta and Saskatchewan and was formed when the precursors to the Front Range of the Rocky Mountains started pushing up to the west. Eroded material from their east-facing drainage basins was carried by streams and rivers and deposited in swampy lowlands, lakes, river channels, and floodplains.<ref name=DAR89>Template:Cite book</ref> The formation is similar in age to the Lourinha Formation in Portugal and the Cañadón Calcáreo Formation in Argentina, Camarasaurid fossils have been found at the 2 formations.<ref name="lz"/><ref name="op">Template:Cite journal</ref> In 1877, it became the center of the Bone Wars, a fossil-collecting rivalry between early paleontologists Othniel Charles Marsh and Edward Drinker Cope, with Camarasaurus itself being discovered and named by the latter Paleontologist during the conflict.
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