Brontosaurus ("thunder lizard") is a genus of sauropod dinosaurs. Originally named by its discoverer Othniel Charles Marsh in 1879, Brontosaurus had long been considered a junior synonym of Apatosaurus; its original species Brontosaurus excelsus was reclassified as A. excelsus in 1903. However, an extensive study published in 2015 by a joint British-Portuguese research team concluded that Brontosaurus was a valid genus of sauropod distinct from Apatosaurus. Nevertheless, not all paleontologists agree with this division. Although the type species, B. excelsus, had long been considered a species of the closely related Apatosaurus, researchers proposed in 2015 that Brontosaurus is a genus separate from Apatosaurus and that it contains three species: B. excelsus, B. yahnahpin, and B. parvus.
Brontosaurus had a long, thin neck and a small head adapted for a herbivorous lifestyle, a bulky, heavy torso, and a long, whip-like tail. The various species lived during the Late Jurassic epoch, in the Morrison Formation of what is now North America, and were extinct by the end of the Jurassic. Adult individuals of Brontosaurus are estimated to have weighed up to 15 tonnes (17 short tons) and measured up to 22 metres (72 feet) long.
The same study classified two additional species that had once been considered Apatosaurus and Eobrontosaurus as Brontosaurus parvus and Brontosaurus yahnahpin respectively. Species of Brontosaurus range in age from 155 to 152 million years ago, during the Kimmeridgian age of the lower to middle Morrison Formation in Wyoming and Utah, United States.
As the archetypal sauropod, Brontosaurus is one of the best-known dinosaurs, and has been featured in film, advertising, and postal stamps, as well as many other types of media.
Description[]
Mounted cast skeleton of B. parvus (UW 15556)
Brontosaurus was a large, long-necked quadrupedal animal with a long, whip-like tail, and forelimbs that were slightly shorter than their hindlimbs. The largest species, B. excelsus, weighed up to 15 tonnes (15 long tons; 17 short tons) and measured up to 22 m (72 ft) long from head to tail.
The skull of Brontosaurus has not been found, but was probably similar to the skull of the closely related Apatosaurus. Like those of other sauropods, the vertebrae of the neck were deeply bifurcated; that is, they carried paired spines, resulting in a wide and deep neck. The vertebral formula was: 15 cervicals, 10 dorsals, five sacrals, and 82 caudals. The caudal vertebra number was noted to vary, even within a species. The cervical vertebrae were stouter than other diplodocids, though not as stout as in mature specimens of Apatosaurus. The dorsal ribs are not fused or tightly attached to their vertebrae, instead being loosely articulated. Ten dorsal ribs are on either side of the body. The large neck was filled with an extensive system of weight-saving air sacs. Brontosaurus, like its close relative Apatosaurus, had tall spines on its vertebrae, which make up more than half the height of the individual bones. The shape of the tail was unusual for diplodocids, being comparatively slender, due to the vertebral spines rapidly decreasing in height the farther they are from the hips. Brontosaurus also had very long ribs compared to most other diplodocids, giving them unusually deep chests. As in other diplodocids, the last portion of the tail of Brontosaurus possessed a whip-like structure.
Restoration of B. excelsus.
The limb bones were also very robust. The arm bones are stout, with the humerus resembling that of Camarasaurus, and those of B. excelsus being nearly identical to those of Apatosaurus ajax. Charles Gilmore in 1936 noted that previous reconstructions erroneously proposed that the radius and ulna could cross, when in life they would have remained parallel. Brontosaurus had a single large claw on each forelimb, and the first three toes possessed claws on each foot. Even by 1936, it was recognized that no sauropod had more than one hand claw preserved, and this one claw is now accepted as the maximum number throughout the entire group. The single front claw bone is slightly curved, and squarely shortened on the front end. The hip bones included robust ilia, and the fused pubes and ischia. The tibia and fibula bones of the lower leg were different from the slender bones of Diplodocus, but nearly indistinguishable from those of Camarasaurus. The fibula is longer than the tibia, although it is also more slender.
History[]
An 1896 diagram of the B. excelsus holotype skeleton by O.C. Marsh. The head is based on material now assigned to Brachiosaurus sp.
In 1879, Othniel Charles Marsh, a professor of paleontology at Yale University, announced the discovery of a large and fairly complete sauropod skeleton from Morrison Formation rocks at Como Bluff, Wyoming. He identified it as belonging to an entirely new genus and species, which he named Brontosaurus excelsus, meaning "thunder lizard", from the Greek brontē/βροντη meaning "thunder" and sauros/σαυρος meaning "lizard", and from the Latin excelsus, "noble" or "high". By this time, the Morrison Formation had become the center of the Bone Wars, a fossil-collecting rivalry between Marsh and another early paleontologist, Edward Drinker Cope. Because of this, the publications and descriptions of taxa by Marsh and Cope were rushed at the time.
Infographic explaining the history of Brontosaurus and Apatosaurus according to Tschopp et al. 2015
Elmer Riggs, in the 1903 edition of Geological Series of the Field Columbian Museum, argued that Brontosaurus was not different enough from Apatosaurus to warrant its own genus, so he created the new combination Apatosaurus excelsus for it. Riggs stated that "In view of these facts the two genera may be regarded as synonymous. As the term 'Apatosaurus' has priority, 'Brontosaurus' will be regarded as a synonym". Nonetheless, before the mounting of the American Museum of Natural History specimen, Henry Fairfield Osborn chose to label the skeleton "Brontosaurus", though he was a strong opponent of Marsh and his taxa.
Obsolete mount of an apatosaurine referred to B. excelsus (specimen AMNH 460) with sculpted skull, completed in 1905, American Museum of Natural History
In 1905, the American Museum of Natural History (AMNH) unveiled the first-ever mounted skeleton of a sauropod, a composite specimen (mainly made of bones from AMNH 460) that they referred to as the species Brontosaurus excelsus. The AMNH specimen was very complete, only missing the feet (feet from the specimen AMNH 592 were added to the mount), lower leg, and shoulder bones (added from AMNH 222), and tail bones (added from AMNH 339). To complete the mount, the rest of the tail was fashioned to appear as Marsh believed it should, which had too few vertebrae. In addition, a sculpted model of what the museum felt the skull of this massive creature might look like was placed on the skeleton. This was not a delicate skull like that of Diplodocus, which would later turn out to be more accurate, but was based on "the biggest, thickest, strongest skull bones, lower jaws and tooth crowns from three different quarries". These skulls were likely those of Camarasaurus, the only other sauropod for which good skull material was known at the time. The mount construction was overseen by Adam Hermann, who failed to find Brontosaurus skulls. Hermann was forced to sculpt a stand-in skull by hand. Henry Fairfield Osborn noted in a publication that the skull was "largely conjectural and based on that of Morosaurus" (now Camarasaurus).
In 1909, an Apatosaurus skull was found, during the first expedition to what would become the Carnegie Quarry at Dinosaur National Monument, led by Earl Douglass. The skull was found a few meters away from a skeleton (specimen CM 3018) identified as the new species Apatosaurus louisae. The skull was designated CM 11162, and was very similar to the skull of Diplodocus. It was accepted as belonging to the Apatosaurus specimen by Douglass and Carnegie Museum director William H. Holland, although other scientists, most notably Osborn, rejected this identification. Holland defended his view in 1914 in an address to the Paleontological Society of America, yet he left the Carnegie Museum mount headless. While some thought Holland was attempting to avoid conflict with Osborn, others suspected that Holland was waiting until an articulated skull and neck were found to confirm the association of the skull and skeleton. After Holland's death in 1934, a cast of a Camarasaurus skull was placed on the mount by museum staff.
At the Yale Peabody Museum, a skeleton was mounted in 1931 with a skull unique from all the others. While at the time most museums were using Camarasaurus casts, the Peabody Museum sculpted a completely different skull. They based the lower jaw on a Camarasaurus mandible, with the cranium resembling Marsh's 1891 illustration. The skull also included forward-pointing nasals, something truly different to any dinosaur, and fenestrae differing from the drawing and other skulls.
The sculpted "Brontosaurus" skull of the Yale Peabody Museum mount, which was based on fossils Camarasaurus and Brachiosaurus.
No apatosaurine skull was mentioned in literature until the 1970s, when John Stanton McIntosh and David Berman redescribed the skulls of Diplodocus and Apatosaurus. They found that though he never published his opinion, Holland was almost certainly correct, that Apatosaurus (and Brontosaurus) had a Diplodocus-like skull. According to them, many skulls long thought to pertain to Diplodocus might instead be those of Apatosaurus. They reassigned multiple skulls to Apatosaurus based on associated and closely associated vertebrae. Though they supported Holland, Apatosaurus was noted to possibly have possessed a Camarasaurus-like skull, based on a disarticulated Camarasaurus-like tooth found at the precise site where an Apatosaurus specimen was found years before. On October 20, 1979, after the publications by McIntosh and Berman, the first skull of an Apatosaurus was mounted on a skeleton in a museum, that of the Carnegie. In 1995, the American Museum of Natural History followed suit, and unveiled their remounted skeleton (now labelled Apatosaurus excelsus) with a corrected tail and a new skull cast from A. louisae. In 1998, the Felch Quarry skull that Marsh included in his 1896 skeletal restoration was suggested to belong to Brachiosaurus instead. In 2011, the first specimen of Apatosaurus where a skull was found articulated with its cervical vertebrae was described. This specimen, CMC VP 7180, was found to differ in both skull and neck features from A. louisae, and the specimen was found to have a majority of features related to those of A. ajax.
Almost all 20th-century paleontologists agreed with Riggs that all Apatosaurus and Brontosaurus species should be classified in a single genus. According to the rules of the ICZN (which governs the scientific names of animals), the name Apatosaurus, having been published first, had priority as the official name; Brontosaurus was considered a junior synonym and was therefore discarded from formal use. Despite this, at least one paleontologist—Robert T. Bakker—argued in the 1990s that A. ajax and A. excelsus are in fact sufficiently distinct that the latter continues to merit a separate genus. In 2015, an extensive study of diplodocid relationships by Emanuel Tschopp, Octavio Mateus, and Roger Benson concluded that Brontosaurus was indeed a valid genus of sauropod distinct from Apatosaurus. The scientists developed a statistical method to more objectively assess differences between fossil genera and species, and concluded that Brontosaurus could be "resurrected" as a valid name. They assigned two former Apatosaurus species, A. parvus and A. yahnahpin, to Brontosaurus, as well as the type species B. excelsus. Paleontologist Michael D'Emic made a critique. Paleontologist Donald Prothero criticized the mass media reaction to this study as superficial and premature, concluding:
Until someone has convincingly addressed the issue, I'm going to put "Brontosaurus" in quotes and not follow the latest media fad, nor will I overrule Riggs (1903) and put the name in my books as a valid genus.[1]
Classification[]
Brontosaurus is a member of the family Diplodocidae, a clade of gigantic sauropod dinosaurs. The family includes some of the longest and largest creatures ever to walk the earth, including Diplodocus, Supersaurus, and Barosaurus. Brontosaurus is also classified in the subfamily Apatosaurinae, which also includes Apatosaurus and one or more possible unnamed genera. Othniel Charles Marsh described Brontosaurus as being allied to Atlantosaurus, within the now defunct group Atlantosauridae. In 1878, Marsh raised his family to the rank of suborder, including Apatosaurus, Brontosaurus, Atlantosaurus, Morosaurus (=Camarasaurus), and Diplodocus. He classified this group within Sauropoda. In 1903, Elmer S. Riggs mentioned that the name Sauropoda would be a junior synonym of earlier names, and grouped Apatosaurus within Opisthocoelia. Most authors still use Sauropoda as the group name.
Skeleton of the AMNH apatosaurine (possibly B. excelsus, specimen AMNH 460) as remounted in 1995
Originally named by its discoverer Othniel Charles Marsh in 1879, Brontosaurus had long been considered a junior synonym of Apatosaurus; its type species, Brontosaurus excelsus, was reclassified as A. excelsus in 1903. However, an extensive study published in 2015 by a joint British-Portuguese research team concluded that Brontosaurus was a valid genus of sauropod distinct from Apatosaurus. Nevertheless, not all paleontologists agree with this division. The same study classified two additional species that had once been considered Apatosaurus and Eobrontosaurus as Brontosaurus parvus and Brontosaurus yahnahpin respectively. Cladogram of the Diplodocidae after Tschopp, Mateus, and Benson (2015):
| Diplodocidae |
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Species[]
Comparison of three specimens and a human: Oklahoma specimen of Apatosaurus ajax (orange), A. louisae (red), and Brontosaurus parvus (green)
- Brontosaurus excelsus, the type species of Brontosaurus, was first named by Marsh in 1879. Many specimens, including the holotype specimen YPM 1980, have been assigned to the species. They include FMNH P25112, the skeleton mounted at the Field Museum of Natural History, which has since been found to represent an unknown species of apatosaurine. Brontosaurus amplus, occasionally assigned to B. parvus, is a junior synonym of B. excelsus. B. excelsus therefore only includes its type specimen and the type specimen of B. amplus. The largest of these specimens is estimated to have weighed up to 15 tonnes and measured up to 22 m (72 ft) long from head to tail. Both known definitive B. excelsus fossils have been reported from Reed’s Quarry 10 of the Morrison Formation Brushy Basin member in Albany County, Wyoming, dated to the late Kimmeridgian age, about 152 million years ago.
- Brontosaurus parvus, first described as Elosaurus in 1902 by Peterson and Gilmore, was reassigned to Apatosaurus in 1994, and to Brontosaurus in 2015. Specimens assigned to this species include the holotype, CM 566 (a partial skeleton of a juvenile found in Sheep Creek Quarry 4 in Albany County, WY), BYU [[1]] (a nearly complete skeleton found in Utah and mounted at Brigham Young University), and the partial skeleton UW 15556 (which had once been accidentally mixed together with the holotype). It dates to the middle Kimmeridgian. Adult specimens are estimated to have weighed up to 14 tonnes and measured up to 22 m (72 ft) long from head to tail.
Left front limb of B. yahnahpin, Morrison Natural History Museum
- Brontosaurus yahnahpin is the oldest species, known from a single site from the lower Morrison Formation, Bertha Quarry, in Albany County, Wyoming, dating to about 155 million years ago. It grew up to 21 metres (69 ft) long. The type species, E. yahnahpin, was described by James Filla and Patrick Redman in 1994 as a species of Apatosaurus (A. yahnahpin). The specific name is derived from Lakota mah-koo yah-nah-pin, "breast necklace", a reference to the pairs of sternal ribs that resemble the hair pipes traditionally worn by the tribe. The holotype specimen is TATE-001, a relatively complete postcranial skeleton found in Wyoming, in the lower Morrison Formation. More fragmentary remains have also been referred to the species. A re-evaluation by Robert T. Bakker in 1998 found it to be more primitive, so Bakker coined the new generic name Eobrontosaurus, derived from Greek eos, "dawn", and Brontosaurus.
The cladogram below is the result of an analysis by Tschopp, Mateus, and Benson (2015). The authors analyzed most diplodocid type specimens separately to deduce which specimen belonged to which species and genus.
| Apatosaurinae |
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Paleobiology[]
Posture and locomotion[]
Tail vertebra of B. excelsus specimen YPM 1980
Cast of B. parvus specimen UWGM 15556 at Tellus Science Museum
Historically, sauropods like Brontosaurus were believed to be too massive to support their own weight on dry land, so theoretically they must have lived partly submerged in water, perhaps in swamps. Recent findings do not support this, and sauropods are thought to have been fully terrestrial animals.
Diplodocids like Brontosaurus are often portrayed with their necks held high up in the air, allowing them to browse on tall trees. Though some studies have suggested that diplodocid necks were less flexible than previously believed, other studies have found that all tetrapods appear to hold their necks at the maximum possible vertical extension when in a normal, alert posture, and argue that the same would hold true for sauropods barring any unknown, unique characteristics that set the soft tissue anatomy of their necks apart from that of other animals.
Trackways of sauropods like Brontosaurus show that the average range for them was around 20–40 km (12–25 mi) per day, and they could potentially reach a top speed of 20–30 km (12–19 mi) per hour. The slow locomotion of sauropods may be due to the minimal muscling or recoil after strides.
Various uses have been proposed for the single claw on the forelimb of sauropods. They were suggested to have been for defence, but the shape and size of them makes this unlikely. Other predictions were that it could be for feeding, but the most probable is that the claw was for grasping objects like tree trunks when rearing.
Physiology[]
James Spotila et al. (1991) suggest that the large body size of Brontosaurus and other sauropods would have made them unable to maintain high metabolic rates, as they would not be able to release enough heat. However, temperatures in the Jurassic were 3 degrees Celsius higher than present. They assumed that the animals had a reptilian respiratory system. Wedel found that an avian system would have allowed them to dump more heat. Some scientists have argued that the heart would have had trouble sustaining sufficient blood pressure to oxygenate the brain.
Juveniles[]
Reconstructed skeleton of a juvenile B. parvus (type specimen CM 566), Carnegie Museum of Natural History
Juvenile Brontosaurus material is known based on the type specimen of B. parvus. The material of this specimen, CM 566, includes vertebrae from various regions, one pelvic bone, and some bones of the hind limb.
Tail[]
An article that appeared in the November 1997 issue of Discover Magazine reported research into the mechanics of diplodocid tails by Nathan Myhrvold, a computer scientist from Microsoft. Myhrvold carried out a computer simulation of the tail, which in diplodocids like Brontosaurus was a very long, tapering structure resembling a bullwhip. This computer modeling suggested that sauropods were capable of producing a whip-like cracking sound of over 200 decibels, comparable to the volume of a cannon.
James Spotila et al. (1991) suggest that the large body size of Brontosaurus and other sauropods would have made them unable to maintain high metabolic rates, as they would not be able to release enough heat. However, temperatures in the Jurassic were 3 degrees Celsius higher than present. They assumed that the animals had a reptilian respiratory system. Wedel found that an avian system would have allowed them to dump more heat. Some scientists have argued that the heart would have had trouble sustaining sufficient blood pressure to oxygenate the brain.Juveniles
Paleoecology[]
The Morrison Formation is a sequence of shallow sea sediments of alluvial origin which, according to radiometric dating, has an age of 156.3 million years at its base, and 146.8 million years at its top, which It covers the late Oxfordian, Kimeridgian and early Tithonian epochs of the Upper Jurassic period. This formation is thought to represent a semi-arid environment with distinct wet and dry seasons. The Morrison Basin, where the dinosaurs lived, stretched from New Mexico in the United States to Alberta and Saskatchewan in Canada, and was formed when the precursors of the Front Range of the Rocky Mountains began to spread westward. Deposits from their eastern drainage basins were carried by streams and rivers to be deposited in swamps and lowlands, lakes, canals and floodplains. This formation is similar in age to the Lourinhã Formation of Portugal and the Tendaguru Formation of Tanzania.
Restoration of a B. excelsus group
Brontosaurus may have been a more solitary animal than other Morrison Formation dinosaurs. As a genus, Brontosaurus existed for a considerable temporal range, and has been found in several levels of the Fm. Morrison. Fossils of B. excelsus have been reported from the upper part of the Salt Wash Member to the upper part of the Brushy Basin Member, which extends from the middle to late Kimeridgian epoch, about 154–151 million years ago. Additional remains are known from even more recent rocks, but these have not been identified as any particular species. Older remains of Brontosaurus have been identified from the mid-Kimeridgian, and have been assigned to B. parvus . Fossils of these animals have been found at the Nine Mile Quarry and the Bone Cabin Quarry in Wyoming and at sites in Colorado, Oklahoma, and Utah, present in stratigraphic zones 2–6.
The Morrison Formation records an environment that was dominated by gigantic sauropod dinosaurs. Morrison's known dinosaurs include the theropods Ceratosaurus , Ornitholestes , and Torvosaurus , the sauropods Apatosaurus , Brachiosaurus , Camarasaurus , and Diplodocus , and the ornithischians Camptosaurus , Dryosaurus , and Stegosaurus . Allosaurus comprises 70 to 75% of theropod specimens and was at the top trophic level of the Morrison food chain. Other vertebrates that shared this paleoenvironment include actinopterygian fish, frogs, salamanders, turtles, sphenodonts, lizards, terrestrial and semi-aquatic crocodylomorphs, and several species of pterosaurs. Shells from bivalves and aquatic snails are also common. The flora of the period has been revealed by fossils of green algae, fungi, mosses, horsetails, cycads, ginkgos, and several families of conifers. The vegetation varied from riparian forests of tree ferns and ferns (gallery forests), to fern savannahs with some trees such as the conifer Brachyphyllum , similar to the modern araucaria.
JPInstitute.com Description[]
Brontosaurus is one of the most well known dinosaurs, but did it really exist? At this point, scientists can't agree on whether Brontosaurus actually existed, as the original type specimen was actually a combination of two different dinosaurs - an Apatosaurus body and a Camarasaurus head. Currently, Brontosaurus is not a valid species, but that may change.
When it was discovered that the head of Camarasaurus was placed on the body of Apatosaurus and called Brontosaurus, most people thought that was the end of this dinosaur that had become an icon for dinosaur fans from the late 19th century through the 1970s. That may not be the case, however, as Dr. Robert Bakker is developing evidence that supports his claim that Brontosaurus should still be recognized as a real dinosaur. He asserts that it was a huge, long-necked plant eater that deserved its name, which means Thunder Lizard.
Appearance in other media[]
Jurassic Park[]
- Brontosaurus appeared in the video game Jurassic Park: Builder.
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Read more Brontosaurus on Jurassic Park Wiki |
The Land Before Time[]
- Brontosaurus had a cameo appeared in The Land Before Time.
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Read more Brontosaurus on Land Before Time Wiki |
We're Back! A Dinosaur's Story[]
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Links[]
References[]
https://en.wikipedia.org/wiki/Brontosaurus
- ↑ Prothero, D. 2015.