Barosaurus ( ) ("heavy lizard") is a genus of large sauropod dinosaur that lived in present-day North America during the Late Jurassic period. It was described by American paleontologist Othniel Charles Marsh in 1890. The genus contains a single valid species, B. lentus, though the African species B. africanus has since been assigned to Tornieria. B. lentus''' holotype (name-bearing) specimen initially consisted of four caudal (tail) vertebrae that were found in 1889 in South Dakota by Ms. Isabella R. Ellerman. However, later excavations found vertebrae, limb bones, and other postcranial remains from the same individual. Several other specimens have been collected outcrops of the Morrison Formation in Utah and Montana, though fossils potentially from the genus have been reported from Colorado, Wyoming, and Oklahoma as well. Barosaurus is known from the Kimmeridgian stage of the Late Jurassic period, which dates to around 152 to 150 million years ago. Barosaurus was an enormous animal, with some adults measuring about in length and weighing about 12–20 metric tons (13–22 short tons). This makes it among the largest diplodocid sauropods. In comparison to its close kin Diplodocus, Barosaurus has a relatively longer neck but shorter tail. Despite this, the tail composed around half the total length of the animal. Barosaurus has 16 cervical vertebrae, more than Diplodocus and Apatosaurus, which are extremely elongated. The back was more compact, with only nine dorsal vertebrae. Barosaurus is a member of the family Diplodocidae, a group of long-tailed sauropods that lived during the Jurassic. The Morrison Formation had a floodplain environment with hot summers and moderate winters. The strata of the Morrison Formation bears a variety of other fossils, including an array of dinosaurs. This includes the theropods Allosaurus and Ceratosaurus, ornithischians Stegosaurus and Dryosaurus, and the other sauropods Brachiosaurus and Brontosaurus.
Discovery, naming, and history
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. Although Marsh did not provide an etymology, he probably intended the name Barosaurus to mean "heavy lizard". In this case, the name would be derived from the Classical Greek words () ("heavy") and () ("lizard"), and the spelling Barysaurus (with an "y") would have been more accurate.
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; in 1898 it was classified by him as a diplodocid for the first time. In his last published paper before his death, Marsh named two smaller metatarsals found by Wieland as a second species, Barosaurus affinis, but this has long been considered a junior synonym of B. lentus.
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. 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. 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.
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) from an attacking Allosaurus fragilis.
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.
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. 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.
Another specimen excavated by Earl Douglass at Carnegie Quarry in the early 20th century was acquired by the Royal Ontario Museum (ROM) in Toronto in a 1962 trade with the Carnegie Museum. At the ROM, the specimen (ROM 3670) remained in storage, with many of the bones lacking a label, and was subsequently forgotten. In 2007, the newly appointed curator of the ROM, paleontologist David Evans, was flying to the U.S. Badlands when he discovered a literature reference to a Barosaurus skeleton in the ROM collection. After returning to Toronto, Evans found many fragments of the skeleton throughout the storage areas. In the rush to put the dinosaur on exhibit within eight weeks before the opening of the museum's new dinosaur exhibition, not all of the many skeletal fragments were mounted.National Geographic, Museum Secrets, Episode 3: Royal Ontario Museum, Segment "Lost Dinosaur". Video clips. . Broadcast December 10, 2012. The ROM specimen is nicknamed "Gordo" after Gordon Edmunds, the museum curator who arranged for the skeleton to be brought to the ROM.Anthony Reinhardt. A monster task - putting Gordo together, The Globe and Mail, November 29, 2007. The specimen is about 40% complete, but as a skull of Barosaurus has never been found, the ROM specimen wears the head of a Diplodocus.National Geographic, Museum Secrets, Episode 3: Royal Ontario Museum, Segment "Lost Dinosaur" . Broadcast December 10, 2012. 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. Nearly in length, the skeletal mount was announced to be the largest dinosaur mount in Canada,Royal Ontario Museum. ROM Channel: Constructing the Barosaurus. Added 2012-08-28. Accessed 2012-12-11. and is a centrepiece of the ROM's dinosaur exhibit, in the James and Louise Temerty Galleries of the Age of Dinosaurs. 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.
Misidentified discoveries in Africa 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). However, this genus name had already been given to the fragmentary remains of a sauropod from England. Both species were moved to a new genus, Tornieria, in 1911. 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. In 1991, "Gigantosaurus" robustus was recognized as a titanosaur and placed in a new genus, Janenschia, as J. robusta. Meanwhile, many paleontologists suspected "Barosaurus" africanus was also distinct from the North American genus, 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. A species of Barosaurus was also allegedly identified from the Kadsi Formation in Zimbabwe in 1987. 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.
DescriptionBarosaurus was an enormous animal, with some adults measuring about in length and weighing about 12–20 metric tons (13–22 short tons).Paul, G.S., 2016, The Princeton Field Guide to Dinosaurs 2nd edition, Princeton University Press p. 213 The estimated tail length of Barosaurus makes up about half the total body length. 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.
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. In 2017, American researcher Keegan M. Melstrom and colleagues assigned an incomplete juvenile diplodocid skeleton (DINO 2921) that had been found at Dinosaur National Monument to Barosaurus. In the same paper, the authors stated that a juvenile diplodocid skull (CM 11255) may belong to the same individual as DINO 2921. However, this cannot be confirmed until the discovery of definitive adult Barosaurus skull material. Tschopp and colleagues (2015) opted to consider CM 11255 an indeterminate diplodocine, although they did mention that some incomplete Barosaurus cranial remains have been mentioned from Howe Quarry. 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.