Barosaurus
Template:Short description Template:Confused Template:Use American English Template:Use mdy dates Template:Speciesbox
Barosaurus (Template:IPAc-en Template:Respell) is a genus of giant, long-tailed, long-necked, plant-eating sauropod dinosaur closely related to the more familiar Diplodocus. Remains have been found in the Morrison Formation from the Upper Jurassic Period of Colorado, Utah, South Dakota, and eastern Wyoming at Como Bluff. It is present in stratigraphic zones 2–5.<ref name="foster-appendix">Foster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327-329.</ref>
The composite term Barosaurus comes from the Greek words barys (βαρυς) meaning "heavy" and sauros (σαυρος) meaning "lizard", thus "heavy lizard".
DescriptionEdit
Barosaurus was an enormous animal, with some adults measuring about Template:Cvt in length and weighing about 12–20 metric tons (13–22 short tons).<ref name=seebacher2001>Template:Cite journal</ref><ref name="Henderson2013">Template:Cite journal</ref><ref name=G.S.Paul2016>Paul, G.S., 2016, The Princeton Field Guide to Dinosaurs 2nd edition, Princeton University Press p. 213</ref> The estimated tail length of Barosaurus makes up about half the total body length.<ref>Template:Cite journal</ref> According to Mike Taylor, the Template:Cvt long vertebra BYU 9024, previously identified as part of the type individual of Supersaurus vivianae,<ref name=lovelaceetal2007/> may actually belong to Barosaurus. He suggested that, interpreted as belonging to Barosaurus, the vertebra suggests an animal that was Template:Cvt long and around Template:Cvt in weight making it one of the largest known dinosaurs, with a neck length of at least Template:Cvt.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In 2020 Molina-Perez and Larramendi estimated it to be slightly smaller at Template:Cvt and Template:Cvt.<ref>Template:Cite book</ref> However, research presented by Brian Curtice at the Society of Vertebrate Paleontology conference has supported the previous interpretation of BYU 9024 as a Supersaurus vertebra.<ref>Template:Cite conference</ref> Despite this, there are other specimens that provide evidence of gigantic Barosaurus individuals which may have been among the longest dinosaurs. One of these is a series of three cervical vertebrae (BYU 3GR/BYU 20815) and the third vertebra is 1110 mm to 1220 mm in length. Dr Mike Taylor and Dr Matt Wedel compared the size of this bone to the same bone in smaller Barosaurus specimens, such as AMNH 6341, and estimated the neck length of the BYU 3GR/20815 Barosaurus at Template:Cvt, which would make it one of the longest necks of any dinosaur and indicate a total body length of around Template:Cvt.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Barosaurus was differently proportioned than its close relative Diplodocus, with a longer neck and shorter tail, but was about the same length overall. It was longer than Apatosaurus, but its skeleton was less robust.<ref name=mcintosh2005>Template:Cite book</ref>
Sauropod skulls are rarely preserved, and scientists have yet to discover a Barosaurus skull. Related diplodocids like Apatosaurus and Diplodocus had long, low skulls with peg-like teeth confined to the front of the jaws.<ref name=upchurchetal2004>Template:Cite book</ref>
Most of the distinguishing skeletal features of Barosaurus were in the vertebrae, although a complete vertebral column has never been found. Diplodocus and Apatosaurus both had 15 cervical (neck) and 10 dorsal (trunk) vertebrae, while Barosaurus had only 9 dorsals. A dorsal may have been converted into a cervical vertebra, for a total of 16 vertebrae in the neck. Barosaurus cervicals were similar to those of Diplodocus, but some were up to 50% longer. The neural spines protruding from the top of the vertebrae were neither as tall or as complex in Barosaurus as they were in Diplodocus. In contrast to its neck vertebrae, Barosaurus had shorter caudal (tail) vertebrae than Diplodocus, resulting in a shorter tail. The chevron bones lining the underside of the tail were forked and had a prominent forward spike, much like the closely related Diplodocus. The tail probably ended in a long whiplash, much like Apatosaurus, Diplodocus and other diplodocids, some of which had up to 80 tail vertebrae.<ref name=mcintosh2005/>
The limb bones of Barosaurus were virtually indistinguishable from those of Diplodocus.<ref name=mcintosh2005/> Both were quadrupedal, with columnar limbs adapted to support the enormous bulk of the animals. Barosaurus had proportionately longer forelimbs than other diplodocids, although they were still shorter than most other groups of sauropods.<ref name=mcintosh2005/> There was a single carpal bone in the wrist, and the metacarpals were more slender than those of Diplodocus.<ref name=foster1996>Template:Cite journal</ref> Barosaurus feet have never been discovered, but like other sauropods, it would have been digitigrade, with all four feet each bearing five small toes. A large claw adorned the inside digit on the manus (forefoot) while smaller claws tipped the inside three digits of the pes (hindfoot).<ref name=mcintosh2005/><ref name=upchurchetal2004/>
Classification and systematicsEdit
Barosaurus is a member of the sauropod family Diplodocidae, and sometimes placed with Diplodocus in the subfamily Diplodocinae.<ref name=lovelaceetal2007>Template:Cite journal</ref> Diplodocids are characterized by long tails with over 70 vertebrae, shorter forelimbs than other sauropods, and numerous features of the skull. Diplodocines like Barosaurus and Diplodocus have slenderer builds and longer necks and tails than apatosaurines, the other subfamily of diplodocids.<ref name=mcintosh2005/><ref name=upchurchetal2004/><ref name=lovelaceetal2007/>
Below is a cladogram of Diplodocinae after Tschopp, Mateus, and Benson (2015).<ref name=TMB2015>Template:Cite journal</ref>
The systematics (evolutionary relationships) of Diplodocidae are becoming better established. Diplodocus has long been regarded as the closest relative of Barosaurus.<ref name=mcintosh2005/><ref name=upchurchetal2004/><ref name=wilson2002>Template:Cite journal</ref> Barosaurus is monospecific, containing only the type species, B. lentus, while at least three species belong to the genus Diplodocus.<ref name=upchurchetal2004/> Another diplodocid genus, Seismosaurus, is considered by many paleontologists to be a junior synonym of Diplodocus as a possible fourth species.<ref name=lucasetal2006>Template:Cite book</ref> Tornieria (formerly "Barosaurus" africanus) and Australodocus from the famous Tendaguru Beds of Tanzania in eastern Africa have also been classified as diplodocines.<ref name=remes2006>Template:Cite journal</ref><ref name=remes2007>Template:Cite journal</ref> With its elongated neck vertebrae, Tornieria may have been particularly closely related to Barosaurus.<ref name=remes2006/> The other subfamily of diplodocids is Apatosaurinae, which includes Apatosaurus and Supersaurus.<ref name=lovelaceetal2007/> The early genus Suuwassea is considered by some to be an apatosaurine,<ref name=lovelaceetal2007/> while others regard it as a basal member of the superfamily Diplodocoidea.<ref name=harris2006>Template:Cite journal</ref> Diplodocid fossils are found in North America, Europe, and Africa. More distantly related within Diplodocoidea are the families Dicraeosauridae and Rebbachisauridae, found only on the southern continents.<ref name=upchurchetal2004/>
Discovery, naming, and historyEdit
The first Barosaurus remains were discovered in the Morrison Formation of South Dakota by Ms. Isabella R. Ellerman, postmistress of Postville, and excavated by Othniel Charles Marsh and John Bell Hatcher of Yale University in 1889. Only six tail vertebrae were recovered at that time, forming the type specimen (YPM 429) of a new species, which Marsh named Barosaurus lentus, from the Classical Greek words {{#invoke:Lang|lang}} ({{#invoke:Lang|lang}}) ("heavy") and {{#invoke:Lang|lang}} ({{#invoke:Lang|lang}}) ("lizard"), and the Latin word {{#invoke:Lang|lang}} ("slow").<ref name=marsh1890>Template:Cite journal</ref> The rest of the type specimen was left in the ground under the protection of the landowner, Ms Rachel Hatch, until it was collected nine years later, in 1898, by Marsh's assistant, George Reber Wieland. These new remains consisted of vertebrae, ribs, and limb bones. In 1896 Marsh had placed Barosaurus in the Atlantosauridae;<ref>Template:Cite journal</ref> in 1898 it was classified by him as a diplodocid for the first time.<ref name=marsh1898>Template:Cite journal</ref> In his last published paper before his death, Marsh named two smaller metatarsals found by Wieland as a second species, Barosaurus affinis,<ref name=marsh1899>Template:Cite journal</ref> but this has long been considered a junior synonym of B. lentus.<ref name=mcintosh2005/><ref name=upchurchetal2004/><ref name=lull1919>Template:Cite journal</ref>
After the turn of the 20th century, Pittsburgh's Carnegie Museum of Natural History sent fossil hunter Earl Douglass to Utah to excavate the Carnegie Quarry in the area now known as Dinosaur National Monument. Four neck vertebrae, each 1 meter (3 feet) long, were collected in 1912 near a specimen of Diplodocus, but a few years later, William Jacob Holland realized they belonged to a different species.<ref name=mcintosh2005/> Meanwhile, the type specimen of Barosaurus had finally been prepared at Yale in the winter of 1917 and was fully described by Richard Swann Lull in 1919.<ref name=lull1919/> Based on Lull's description, Holland referred the vertebrae (CM 1198), along with a second partial skeleton found by Douglass in 1918 (CM 11984), to Barosaurus. This second Carnegie specimen remains in the rock wall at Dinosaur National Monument and was not fully prepared until the 1980s.<ref name=mcintosh2005/>
The most complete specimen of Barosaurus lentus was excavated from the Carnegie Quarry in 1923 by Douglass, now working for the University of Utah after the death of U.S. Steel founder Andrew Carnegie, who had been financing Douglass' earlier work in Pittsburgh. Material from this specimen was originally spread across three institutions. Most of the back vertebrae, ribs, pelvis, hindlimb and most of the tail stayed at the University of Utah, while the neck vertebrae, some back vertebrae, the shoulder girdle and forelimb were shipped to the National Museum of Natural History in Washington D.C., and a small section of tail vertebrae ended up in the Carnegie Museum in Pittsburgh. However, in 1929 Barnum Brown arranged for all of the material to be shipped to the American Museum of Natural History in New York City, where it remains today. A cast of this specimen (AMNH 6341) was controversially mounted in the lobby of the American Museum, rearing up to defend its young (AMNH 7530, now classified as Kaatedocus siberi<ref name=TMB2015/>) from an attacking Allosaurus fragilis.<ref name=mcintosh2005/>
More recently, more vertebrae and a pelvis were recovered in South Dakota. This material (SDSM 25210 and 25331) is stored in the collection of the South Dakota School of Mines and Technology in Rapid City.<ref name=foster1996/>
Darren Naish has noted a common error in books of the late 20th century to depict Barosaurus as a kind of brachiosaur-like short tailed sauropod with raphes on its neck and body, and often curving the upper half of its neck downwards into a U-shape, citing it as an example of a Palaeoart meme.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref> This originated with a drawing by Robert Bakker in a 1968 article, in which two Barosaurus appeared to have short tails due to a mix of foreshortening and one obscuring the other.
In 2007, paleontologist David Evans was flying to the U.S. Badlands when he discovered reference to a Barosaurus skeleton (ROM 3670) in the collection of the Royal Ontario Museum in Toronto, where he had recently become a curator. Earl Douglass had excavated this specimen at the Carnegie Quarry in the early 20th century; the ROM acquired it in a 1962 trade with the Carnegie Museum. The specimen was never exhibited and remained in storage until its rediscovery by David Evans 45 years later. He returned to Toronto and searched the storage areas and found many fragments, large and small, of the skeleton. It is now a centrepiece of the ROM's dinosaur exhibit, in the James and Louise Temerty Galleries of the Age of Dinosaurs.<ref name=ROM2007>Template:Cite press release </ref> At almost 27.5 meters (90 feet) long, the specimen is the largest dinosaur ever to be mounted in Canada.<ref name=rom1>Royal Ontario Museum. ROM Channel: Constructing the Barosaurus. Added 2012-08-28. Accessed 2012-12-11.</ref> The specimen is about 40% complete. As a skull of Barosaurus has never been found, the ROM specimen wears the head of a Diplodocus.<ref name=ms1>National Geographic, Museum Secrets, Episode 3: Royal Ontario Museum, Segment "Lost Dinosaur" Template:Webarchive. Broadcast December 10, 2012.</ref> Each bone is mounted on a separate armature so that it can be removed from the skeleton for study and then replaced without disturbing the rest of the skeleton. (See video "Dino Workshop" at reference.)<ref name=ms2/> In the rush to put the dinosaur on exhibit within ten weeks of its delivery to Research Casting International in 2500 pieces, not all of the skeletal fragments were mounted. In addition, more bones labeled ROM 3670 are still being found in storage. In the future, more may be added to the specimen and it may turn out to be the most complete known.' (See video "Dino Assembly" at reference.)<ref name=ms2>National Geographic, Museum Secrets, Episode 3: Royal Ontario Museum, Segment "Lost Dinosaur". Video clips. Template:Webarchive. Broadcast December 10, 2012.</ref> The ROM specimen is nicknamed "Gordo" after Gordon Edmunds, the museum curator who arranged for the skeleton to be brought to the ROM, and who had hoped to display it fully but was unable to.<ref name=rom1/><ref>Anthony Reinhardt. A monster task - putting Gordo together, The Globe and Mail, November 29, 2007.</ref><ref>Zain Ahmed. Gordo the Barosaurus. Atlas Obscura. March 15, 2021.</ref> John McIntosh believes that the ROM's skeleton is the same individual represented by four neck vertebrae labeled "CM 1198" in the collection of the Carnegie Museum.<ref name=mcintosh2005/>
Discoveries in AfricaEdit
In 1907, German paleontologist Eberhard Fraas discovered the skeletons of two sauropods on an expedition to the Tendaguru Beds in German East Africa (now Tanzania). He classified both specimens in the new genus Gigantosaurus, with each skeleton representing a new species (G. africanus and G. robustus).<ref name=fraas1908> Template:Cite journal</ref> However, this genus name had already been given to the fragmentary remains of a sauropod from England.<ref name=seeley1869> Template:Cite book</ref> Both species were moved to a new genus, Tornieria, in 1911.<ref name=sternfeld1911>Template:Cite journal</ref> Upon further study of these remains and many other sauropod fossils from the hugely productive Tendaguru Beds, Werner Janensch moved the species once again, this time to the North American genus Barosaurus.<ref name=janensch1922> Template:Cite journal </ref> In 1991, "Gigantosaurus" robustus was recognized as a titanosaur and placed in a new genus, Janenschia, as J. robusta.<ref name=wild1991> Template:Cite journal</ref> Meanwhile, many paleontologists suspected "Barosaurus" africanus was also distinct from the North American genus,<ref name=mcintosh2005/><ref name=upchurchetal2004/> which was confirmed when the material was redescribed in 2006. The African species, although closely related to Barosaurus lentus and Diplodocus from North America, is now once again known as Tornieria africana.<ref name=remes2006/> A species of Barosaurus was also allegedly identified from the Kadsi Formation in Zimbabwe in 1987.<ref>Template:Cite journal</ref> However, this material is poorly preserved and fragmentary and was not adequately diagnosed as such, and so its referral to Barosaurus is doubtful. It may represent Tornieria.<ref>Template:Cite journal</ref>
PaleobiologyEdit
FeedingEdit
The structure of the cervical vertebrae of Barosaurus allowed for a significant degree of lateral flexibility in the neck, but restricted vertical flexibility. This suggests a different feeding style for this genus when compared to other diplodocids.<ref>Template:Cite journal</ref> Barosaurus swept its neck in long arcs at ground level when feeding, which resembled the strategy that was first proposed by John Martin in 1987.<ref>Martin, John. 1987. Mobility and feeding of Cetiosaurus (Saurischia, Sauropoda) – why the long neck? pp. 154–159 in P. J. Currie and E. H. Koster (eds), Fourth Symposium on Mesozoic Terrestrial Ecosystems, Short Papers. Boxtree Books, Drumheller (Alberta). 239 pages.</ref> The restriction in vertical flexibility suggests that Barosaurus did not primarily feed on vegetation that was high off the ground.
PaleoecologyEdit
Barosaurus remains are limited to the Morrison Formation, which is widespread in the western United States between the Great Plains and Rocky Mountains.<ref name=mcintosh2005/><ref name=upchurchetal2004/> Radiometric dating agrees with biostratigraphic and paleomagnetic studies, indicating that the Morrison was deposited during the Kimmeridgian and early Tithonian stages of the Late Jurassic Period,<ref name=turnerpeterson2004>Template:Cite book</ref> or approximately 155 to 148 million years ago.<ref name=kowallisetal1998>Template:Cite book</ref> Barosaurus fossils are found in late Kimmeridgian to early Tithonian sediments,<ref name=TMB2015/> around 150 million years old.<ref name=turnerpeterson2004/>
The Morrison Formation was deposited in floodplains along the edge of the ancient Sundance Sea, an arm of the Arctic Ocean which extended southward to cover the middle of North America as far south as the modern state of Colorado. Due to tectonic uplift to the west, the sea was receding to the north, and had retreated into what is now Canada by the time Barosaurus evolved. The sediments of the Morrison were washed down out of the western highlands, which had been uplifted during the earlier Nevadan orogeny and were now eroding.<ref name=turnerpeterson2004/> Very high atmospheric concentrations of carbon dioxide in the Late Jurassic led to high temperatures around the globe, due to the greenhouse effect. One study, estimating CO2 concentrations of 1120 parts per million, predicted average winter temperatures in western North America of Template:Convert and summer temperatures averaging Template:Convert.<ref name=mooreetal1992>Template:Cite journal</ref> A more recent study suggested even higher CO2 concentrations of up to 3180 parts per million.<ref name=ekartetal1999>Template:Cite journal</ref> Warm temperatures that led to significant evaporation year-round, along with possible rain shadow effect from the mountains to the west,<ref name=demkoparrish1998>Template:Cite book</ref> led to a semi-arid climate with only seasonal rainfall.<ref name=turnerpeterson2004/><ref name=engelmannetal2004>Template:Cite book</ref> This formation is similar in age to the Solnhofen limestone Formation in Germany and the Tendaguru Formation in Tanzania. In 1877 this formation became the center of the Bone Wars, a fossil-collecting rivalry between early paleontologists Othniel Charles Marsh and Edward Drinker Cope.
The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as Camarasaurus, Diplodocus, Apatosaurus and Brachiosaurus. Dinosaurs that lived alongside Barosaurus included the herbivorous ornithischians Camptosaurus, Dryosaurus, Stegosaurus and Othnielosaurus, and predators in this paleoenvironment included the theropods Saurophaganax, Allosaurus, Torvosaurus, Ceratosaurus, Marshosaurus, Stokesosaurus and Ornitholestes.<ref>Template:Cite book</ref> Allosaurus accounted for 70 to 75% of theropod specimens and was almost at the top trophic level of the Morrison food web.<ref name=JRF03a>Template:Cite book</ref> Other vertebrates that shared this paleoenvironment included ray-finned fishes, frogs, salamanders, turtles, sphenodonts, lizards, terrestrial and aquatic crocodylomorphs, and several species of pterosaur. Early mammals were present such as docodonts, multituberculates, symmetrodonts, and triconodonts. The flora of the period has been revealed by fossils of green algae, fungi, mosses, horsetails, cycads, ginkgoes, and several families of conifers. Vegetation varied from river-lining forests of tree ferns, and ferns (gallery forests), to fern savannas with occasional trees such as the Araucaria-like conifer Brachyphyllum.<ref name=KC06>Template:Cite book</ref>
Assistant Curator David Evans mounted the ROM specimen conservatively, with a relatively low head to give the dinosaur moderate blood pressure.<ref name=ms1/> The extremely long neck, 10 meters (30 feet) may have developed to enable Barosaurus to feed over a wide area without moving around; it may also have enabled the dinosaurs to radiate excess body heat. Evans suggests that sexual selection might have favored those with longer necks. (See video "Neck Impossible" at reference.)<ref name=ms2/>
ReferencesEdit
Books:
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