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Brontosaurus (; meaning "thunder lizard" from the Ancient Greek words βροντή, "thunder" and σαῦρος, "lizard") is a genus of herbivorous sauropod dinosaur that lived in present-day United States during the Late Jurassic period. It was described by American paleontologist Othniel Charles Marsh in 1879, the type species being dubbed B. excelsus, based on a partial skeleton lacking a skull found in Como Bluff, Wyoming. In subsequent years, two more species of Brontosaurus were named: B. parvus in 1902 and B. yahnahpin in 1994. Brontosaurus lived about 156 to 146 million years ago (mya) during the Kimmeridgian and Tithonian ages in the Morrison Formation of what is now Utah and Wyoming. For decades, the animal was thought to have been a taxonomic synonym of its close relative Apatosaurus, but a 2015 study by Emmanuel Tschopp and colleagues found it to be distinct. It has seen widespread representation in popular culture, being the archetypal "long-necked" dinosaur in general media.
The anatomy of Brontosaurus is well known, with fossils demonstrating that it was large, long-necked, and quadrupedal with a long tail terminating in a whip-like structure. The cervical vertebrae are notably extremely robust and heavily built, in contrast to its lightly built relatives Diplodocus and Barosaurus. The forelimbs were short and stout whereas the hindlimbs were elongated and thick, supported respectively by a heavily built shoulder girdle and pelvis. Several size estimates have been made, with the largest species B. excelsus reaching up to from head to tail and weighing in at , whereas the smaller B. parvus only got up to long. Juvenile specimens of Brontosaurus are known, with younger individuals growing rapidly to adult size in as little as 15 years.
Brontosaurus has been classified within the family Diplodocidae, which was a group of sauropods that had shorter necks and longer tails compared to other families like brachiosaurs and mamenchisaurs. Diplodocids first evolved in the Middle Jurassic but peaked in diversity during the Late Jurassic with forms like Brontosaurus before becoming extinct in the Early Cretaceous. Brontosaurus is a genus in the subfamily Apatosaurinae, which includes only it and Apatosaurus, which are distinguished by their firm builds and thick necks. Although Apatosaurinae was named in 1929, the group was not used validly until an extensive 2015 paper, which found Brontosaurus to be valid. However, the status of Brontosaurus is still uncertain, with some paleontologists still considering it a synonym of Apatosaurus.
Being from the Morrison Formation, Brontosaurus coexisted with a menagerie of other taxa such as the sauropods Diplodocus, Barosaurus, and Brachiosaurus; herbivorous Stegosaurus, Dryosaurus, and Nanosaurus; as well as the carnivorous theropods Allosaurus, Marshosaurus and Ceratosaurus. This formation was a hotspot of sauropod biodiversity, with over 16 recognized genera, which resulted in niche partitioning between different sauropods.
In August 1883, Marshall P. Felch collected a disarticulated partial skull (USNM V 5730) of a sauropod further south in the Felch Quarry at Garden Park, Colorado and sent the specimen to Yale. (1998). 9789056991838, Taylor & Francis. ISBN 9789056991838 Marsh referred the skull to B. excelsus, later featuring it in a skeletal reconstruction of the B. excelsus type specimen in 1891 and the illustration was featured again in Marsh's landmark publication, The Dinosaurs of North America, in 1896. At the Yale Peabody Museum, the skeleton of Brontosaurus excelsus was mounted in 1931 with a skull based on the Marsh reconstruction of the Felch Quarry skull. While at the time most museums were using Camarasaurus casts for skulls, the Peabody Museum sculpted a completely different skull based on Marsh's recon. Marsh's skull was inaccurate for several other reasons: it included forward-pointing nasals, something truly different to any other dinosaur, and fenestrae differing from the drawing and other skulls. The mandible was based on a Camarasaurus
In the 1903 edition of Geological Series of the Field Columbian Museum, Elmer Riggs argued that Brontosaurus was not different enough from Apatosaurus to warrant a separate 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. 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 Brontosaurus excelsus. The AMNH specimen was very complete, only missing the 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.Norell, M.A., Gaffney, E.S., & Dingus, L. (1995). Discovering Dinosaurs in the American Museum of Natural History. New York: Alfred A. Knopf, Inc. To finish the mount, the rest of the tail was fashioned to appear as Marsh believed it should, which meant it had too few vertebrae. In addition, a sculpted model of what the museum felt the skull of this massive creature might have looked 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 of 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 J. 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.
Another specimen of an Apatosaurine now referred to Brontosaurus was discovered in 1993 by the Tate Geological Museum, also from the Morrison Formation of central Wyoming. The specimen consisted of a partial postcranial skeleton, including a complete manus and multiple vertebrae, and was described by James Filla and Pat Redman a year later. Filla and Redman named the specimen Apatosaurus yahnahpin ("yahnahpin-wearing deceptive lizard"), but Robert T. Bakker gave it the genus name Eobrontosaurus in 1998. Bakker believed that Eobrontosaurus was the direct predecessor to Brontosaurus, although Tschopp et al.'s phylogenetic analysis placed B. yahnahpin as the basalmost species of Brontosaurus.
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; 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 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. The publication was met with some criticism from other paleontologists, including Michael D'Emic, Donald Prothero, who criticized the mass media reaction to this study as superficial and premature,Prothero, D. 2015. "Is "Brontosaurus" Back? Not So Fast!". Skeptic.com and many others below. Some paleontologists, such as John and ReBecca Foster, continue to consider Brontosaurus as a synonym of Apatosaurus.
Like those of other diplodocids, the vertebrae of the neck were deeply bifurcated on the dorsal side; that is, they carried paired spines, resulting in a wide and deep neck. The spine and tail consisted of 15 cervicals, ten dorsals, five sacrals, and about 82 caudals, based on Apatosaurus. The number of caudal vertebrae has been noted to vary, even within a species. Vertebrae in the neck, torso, and sacrum of sauropods bore large pneumatic foramina on their lateral sides. These are used to lighten the bones which aided in keeping the animal lighter. Within the vertebrae as well, smooth bone walls in addition to Diverticulum would make pockets of air to keep the bones light.Wedel, M. J. (2005). Postcranial skeletal pneumaticity in sauropods and its implications for mass estimates. The sauropods: evolution and paleobiology. University of California Press, Berkeley, 201-228. Similar structures are observable in birds and large mammals. The cervical vertebrae were stouter than those of other diplodocids, as in Apatosaurus. On the lateral sides of the cervicals, apatosaurines had well-developed and thick parapophyses (extensions on the lateral sides of the vertebrae that attached to cervical ribs) which would point ventrally under the Vertebra. These parapophyses in conjunction with dense Vertebra and were strong anchors for neck muscles, which could sustain extreme force. The cervicals were also more boxy than in other sauropods due to their truncated zygapophyses and tall build.Wedel, M. J., Sanders, R. K., & Cuozzo, F. P. (2002). Osteological correlates of cervical musculature in Aves and Sauropoda (Dinosauria: Saurischia), with comments on the cervical ribs of Apatosaurus. Museum of Paleontology, University of California, Berkeley. These vertebrae are triangular in anterior view, whereas they most often are rounded or square in genera like Camarasaurus. Despite its pneumaticy, the neck of Brontosaurus is thought to have been double the mass of that of other diplodocids due to the former's sturdiness. Brontosaurus differs from Apatosaurus in that the base of the posterior dorsal vertebrae's Vertebra are longer than they are wide. The cervicals of species within Brontosaurus also vary, such as the lack of Tubercle on the neural spines of B. excelsus and the lateral expansion of unbifurcated neural spines in B. parvus.
Its dorsal vertebrae had short centra with large fossae (shallow excavations) on their lateral sides, though not as extensively as the cervicals'. Neural canals, which contain the spinal cord of the vertebral column, are ovate and large in the dorsals. The diapophyses protrude outward and curve downward in a hook-shape. Neural spines are thick in anterior-posterior view with a bifurcate top. The neural spines of the dorsals would increase in height further towards the tail, creating an arched back. Apatosaurine neural spines compose more than half the height of the vertebrae. Medial surfaces of neural spines are gently rounded in B. yahnahpin, whereas in other B. spp. they are not. The dorsal ribs are not fused or tightly attached to their vertebrae, instead being loosely articulated. Ten Rib cage are on either side of the body. Expanded excavations within the sacrum are present making it into a hollow cylinder-shape. Sacral neural spines are fused together into a thin plate. The posteriormost caudal vertebra was lightly fused to the sacral vertebrae, becoming part of the plate. Internally, the Neural tube was enlarged.Osborn, H. F. (1904). Manus, sacrum, and caudals of Sauropoda (Vol. 3). The shape of the tail was typical of diplodocids, being comparatively slender, due to the vertebral spines rapidly decreasing in height the farther they are from the hips. As in other diplodocids, the last portion of the tail of Brontosaurus possessed a whip-like structure. The tail also bears an extensive air-sac system to lighten its weight, as observed in specimens of B. parvus.
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 which faced towards the body, whereas the rest of the Phalanx bone lacked . 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 metacarpals are elongated and thinner than the phalanges, bearing boxy articular ends on its proximal and distal faces. The single front claw bone is slightly curved and squarely shortened on the front end. The phalangeal formula is 2-1-1-1-1, meaning the innermost finger (phalanx) on the forelimb has two bones and the next has one. The single manual claw bone (ungual) is slightly curved and squarely truncated on the anterior end. Proportions of the manus bones vary within Apatosaurinae as well, with B. yahnahpin
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.D'Emic, M. 2015. "Not so fast, Brontosaurus" . Time.com 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):
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.
Various uses for the single claw on the forelimb of sauropods have been proposed. One suggestion is that they were used for defense, but their shape and size make this unlikely. It was also possible they were for foraging, but the most probable use for the claw was grasping objects such as tree trunks when rearing.
Trackways of sauropods like Brontosaurus show that the average range for them was around per day, and they could potentially reach a top speed of .Fastovsky, D.E.; Weishampel, D.B. (2009). Dinosaurs: A Concise Natural History (PDF). Cambridge University Press. pp. 165–200. . Archived from the original (PDF) on September 24, 2015. The slow locomotion of sauropods may be due to the minimal muscling or recoil after strides. A possible bipedal trackway of a juvenile Apatosaurus is known, but it is disputed if it was possible for the sauropod.
Given the large body mass and long neck of sauropods like Brontosaurus, physiologists have encountered problems determining how these animals breathed. Beginning with the assumption that, like , Brontosaurus did not have a diaphragm, the dead-space volume (the amount of unused air remaining in the mouth, trachea, and air tubes after each breath) has been estimated at for a specimen. Paladino calculates its Lung volumes (the amount of air moved in or out during a single breath) at with an avian respiratory system, if mammalian, and if reptilian.
Based on this, its respiratory system would likely have consisted of parabronchi, with multiple pulmonary air sacs as in avian lungs, and a flow-through lung. An avian respiratory system would need a lung volume of about compared with a mammalian requirement of , which would exceed the space available. The overall thoracic volume of the same-sized Apatosaurus has been estimated at , allowing for a , four-chambered heart and a lung capacity. That would allow about for the necessary tissue. Evidence for the avian system in Brontosaurus and other sauropods is also present in the pneumaticity of the vertebrae. Though this plays a role in reducing the weight of the animal, Wedel (2003) states they are also likely connected to air sacs, as in birds.
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 hindlimb. When describing B. parvus, Peterson and Gilmore noted that the neural spines were sutured, the sacral vertebrae were unfused, and the coracoid was missing. All of these features are signs of immaturity in other archosaurs, showing that sauropods had these traits too. Peterson and Gilmore also theorized that sauropods never stopped growing, which supposedly helped in attaining their massive size, a concept unsupported by fossils.
However, Rega (2012) notes that Camarasaurus while lacking a tailwhip, displays a similar level of caudal co-ossification and that Mamenchisaurus while having the same pattern of vertebral metrics, lacks a tailwhip and does not display fusion in any "transitional region". Also, the crush fractures which would be expected if the tail was used as a whip have never been found in diplodocids. More recently, Baron (2020) has considered the use of the tail as a bullwhip unlikely because of the potentially catastrophic muscle and skeletal damage such speeds could cause on the large and heavy tail. Instead, he proposes that the tails might have been used as a tactile organ to keep in touch with the individuals behind and to the sides of the animal in a group, which could have augmented cohesion and allowed communication among individuals while limiting more energetically demanding activities like stopping to search for dispersed individuals, turning to visually check on others behind, or communicating vocally.
Brontosaurus may have been a more solitary animal than other Morrison Formation dinosaurs. As a genus, Brontosaurus existed for a long interval, and was found in most levels of the Morrison. B. excelsus fossils have been reported from only the Brushy Basin Member, dating to the late Kimmeridgian age, about 151 Mya. Older Brontosaurus remains have also been identified from the middle Kimmeridgian, and are assigned to B. parvus. Fossils of these animals have been found in Nine Mile Quarry and Bone Cabin Quarry in Wyoming and at sites in Colorado, Oklahoma, and Utah, present in stratigraphic zones 2–6 according to John Foster's model.
The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs. Dinosaurs known from the Morrison include the theropods Ceratosaurus, Ornitholestes, and Allosaurus, the sauropods Apatosaurus, Brachiosaurus, Camarasaurus, and Diplodocus, and the Camptosaurus, Dryosaurus, and Stegosaurus. Other vertebrates that shared this paleoenvironment included actinopterygii, , , , sphenodontia, , terrestrial and aquatic crocodylomorpha, and several species of . Shells of and aquatic , are also common. The flora of the period has been revealed by fossils of chlorophyta, , equisetum, , , and several families of . Vegetation varied from river-lining forests of and ferns (), to fern with occasional trees such as the Araucaria-like conifer Brachyphyllum.
Sinclair Oil Corporation has long been a fixture of American roads (and briefly in other countries) with its green dinosaur logo and mascot, a Brontosaurus. While Sinclair's early advertising included a number of different dinosaurs, eventually only Brontosaurus was used as the official logo, due to its popular appeal.
As late as 1989, the U.S. Postal Service faced controversy when it issued four "dinosaur" stamps: Tyrannosaurus, Stegosaurus, Pteranodon, and Brontosaurus. The use of the term Brontosaurus in place of Apatosaurus led to complaints of "fostering scientific illiteracy." The Postal Service defended itself (in Postal Bulletin 21742) by saying, "Although now recognized by the scientific community as Apatosaurus, the name Brontosaurus was used for the stamp because it is more familiar to the general population." Indeed, the Postal Service even implicitly rebuked the somewhat inconsistent complaints by adding that "similarly, the term 'dinosaur' has been used generically to describe all the animals i.e.,, even though the Pteranodon was a flying reptile rather," a distinction left unmentioned in the numerous correspondence regarding the Brontosaurus/ Apatosaurus issue. Palaeontologist Stephen Jay Gould supported this position. In the essay from which the title of the 1991 collection Bully for Brontosaurus is taken, Gould wrote: "Touché and right on; no one bitched about Pteranodon, and that's a real error." His position, however, was not one suggesting the exclusive use of the popular name; he echoed Riggs' original argument that Brontosaurus is a synonym for Apatosaurus. Nevertheless, he noted that the former has developed and continues to maintain an independent existence in the popular imagination.
American alternative rock band They Might Be Giants for their studio album Book (2021) has a song called "Brontosaurus", being described by AllMusic as one that "uncovers the sensitivity of someone seemingly impervious in a tale that resembles Dumbo as a depressed dinosaur".
The more vociferous denunciations of the usage have elicited sharply defensive statements from those who would not wish to see the name be struck from official usage. Tschopp's study has generated a very high number of responses from many, often opposed, of editorial, news staff, and personal blog nature (both related and not), from both sides of the debate, from related and unrelated contexts, and from all over the world.
Since Wedel et al 2015 preprint, various reconstructions of Brontosaurus individuals engaging in intraspecific combat based on their study have been made. The art typically depicts the neck-battling hypothesis stipulated by their research. Many of these works are published online under the hashtag "#BrontoSmash".
Species
Paleobiology
When Brontosaurus was described in 1879, the widespread notion in the scientific community was that sauropods were Semiaquatic, lethargic reptiles that were inactive.Taylor, M.P. (2010). "Sauropod dinosaur research: a historical review". In Richard Moody, Eric Buffetaut, David M. Martill and Darren Naish (eds.), Dinosaurs (and other extinct saurians): a historical perspective. HTML abstract. In Othniel Marsh's publication The Dinosaurs of North America, he described the dinosaur as "more or less amphibious, and its food was probably aquatic plants or other succulent vegetation". This is unsupported by fossil evidence. Instead, sauropods were active and had adaptations for dwelling on land. Marsh also noted the animal's supposed lack of intellect based on the small Neurocranium of the Felch Quarry skull and slender Nervous system. Recent research has found signs of intelligence in dinosaurs, akin to modern birds, though sauropods had relatively small brains.Russell, Dale A. (1997). "Intelligence". In Kevin Padian; Philip J. Currie (eds.). Encyclopedia of dinosaurs. San Diego: Academic Press. pp. 370–372. .
Diet and energy requirements
Being a diplodocid sauropod, Brontosaurus was herbivorous and fed on , Bennettitales, seed ferns, and Equisetum, eating at ground height as a nonselective browser. The replacement method and physiology of Apatosauruss teeth is unique, with the entire tooth row being replaced at once and up to 60% more often than Diplodocus. The teeth of Apatosaurus are thick, lack denticles, and are strongly cylindrical in cross-section whereas they are long, slender, and elliptical in cross-section in Diplodocus. These characteristics imply that Apatosaurus, and likely Brontosaurus, consumed tougher vegetation than Diplodocus. Diplodocids in general also have shorter necks than the long-necked, vertically inclined macronarians. This would result in niche partitioning, the various taxa thus avoiding direct competition with each other due to feeding on different plants and at different heights. Hypotheses of the food requirements of Brontosaurus have been made, though predicting this is difficult due to the lack of modern analogues. (mammals) and (reptiles) require a specific amount of nutrition to survive which correlates with their metabolism as well as body size. Estimations of the dietary necessities of Brontosaurus were made in 2010, with a guess of 2•10^4 to 50•10^4 Joule needed daily. This led to hypotheses on the distributions of Brontosaurus to meet this requirement, though they varied on whether it was an ectotherm or endotherm. If Brontosaurus was an endotherm, fewer adult individuals could be sustained than if it were an ectotherm, which could have tens of animals per square kilometer.Farlow JO, Coroian ID, Foster JR (2010) Giants on the landscape: modelling the abundance of megaherbivorous dinosaurs of the Morrison formation (late Jurassic, western USA). Hist Biol 22:403–429Farlow JO (1976) A consideration of the trophic dynamics of a Late Cretaceous large-dinosaur community (Oldman formation). Ecology 57:841–857 Due to this, it has been theorized that Brontosaurus and other sauropods living within the arid environment of the Morrison Formation participated in migrations between feeding sites. James Farlow (1987) calculates that a Brontosaurus-sized dinosaur about would have possessed of fermentation contents. Assuming Apatosaurus had an avian respiratory system and a reptilian resting-metabolism, Frank Paladino etal. (1997) estimate the animal would have needed to consume only about of water per day. (1997). 9780253333490, Indiana University Press. ISBN 9780253333490
Posture
Historically, sauropods like Brontosaurus were believed to have been too massive to support their 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 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.
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. Furthermore, they assumed that the animals had a reptilian respiratory system. Matt Wedel found that an avian system would have allowed them to dump more heat. Some scientists have also argued that the heart would have had trouble sustaining sufficient blood pressure to oxygenate the brain.
Juveniles
A 1999 microscopic study of Apatosaurus and Brontosaurus bones concluded the animals grew rapidly when young and reached near-adult sizes in about 10years. In 2008, a study on the growth rates of sauropods was published by biologists Thomas Lehman and Holly Woodward. They said that by using growth lines and length-to-mass ratios, Apatosaurus would have grown to 25t (25 long tons; 28 short tons) in 15years, with growth peaking at in a single year. An alternative method, using limb length and body mass, found Brontosaurus and Apatosaurus grew per year, and reached their full mass before it was about 70years old. These estimates have been called unreliable because the calculation methods are not sound; old growth lines would have been obliterated by bone remodeling. One of the first identified growth factors of Apatosaurus was the number of sacral vertebrae, which increased to five by the time of the creature's maturity. This was first noted in 1903 and again in 1936.
Tail
The estimated tail length of Brontosaurus is approximately 56% of the total body length, with the tail sometimes hypothesized to be capable of functioning like a very long, tapering bullwhip. 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 at 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 , comparable to the volume of a cannon. There is some circumstantial evidence supporting this as well: a number of diplodocids have been found with fused or damaged tail vertebrae, which may be a symptom of cracking their tails: these are particularly common between the 18th and the 25th caudal vertebra, a region the authors consider a transitional zone between the stiff muscular base and the flexible whiplike section.
Neck combat
The cervical vertebrae of Brontosaurus and Apatosaurus are robust, which has led to speculation on the use of these structures. These structures had expensive energy requirements, so the reason for their evolution must have been important to the animal. Notable features include dense cervical ribs and diapophyses, ribs that are angled ventrally, and an overall subtriangular cross-section. These traits are in contrast to the more fragile cervicals of diplodocines. Cervical ribs acted as anchors for the longus colli ventralis and flexer colli lateralis muscles, which are used in the downward motion of the neck. Stronger muscles for ventral motions allowed more force to be exerted downward. The cervical ribs formed a "V"-shape, which could be used to shelter the softer underlying tissues of the neck from damage. Ventral sides of the cervical ribs were capped by round, protruding processes. These have been suggested to have been attachment points for bosses or spikes. A preprint by Wedel et al (2015) thought that due to the combination of these traits, Brontosaurus would use its neck for combat between individuals through the use of striking necks. Behavior like this has been observed in other animals like giraffes and large tortoises.Hone, D. W. E., & Naish, D. (2013). The 'species recognition hypothesis' does not explain the presence and evolution of exaggerated structures in non-avialan dinosaurs. Journal of Zoology 290(3):172-180.
Paleoecology
The Morrison Formation is a sequence of shallow marine and alluvial sediments which, according to radiometric dating, ranges between 156.3 million years old (Mya) at its base, and 146.8 Mya at the top, which places it in the late Oxfordian stage, Kimmeridgian, and early Tithonian faunal stages of the Late Jurassic period. This formation is interpreted as a semi-arid environment with distinct wet season and . The Morrison Basin, where dinosaurs lived, stretched 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. The deposits from their east-facing were carried by streams and and deposited in lowlands, lakes, river channels, and . This formation is similar in age to the Lourinhã Formation in Portugal and the Tendaguru Formation in Tanzania.
In popular culture
The length of time taken for Riggs's 1903 reclassification of Brontosaurus as Apatosaurus to be brought to public notice, as well as Osborn's insistence that the Brontosaurus name be retained despite Riggs's paper, meant that Brontosaurus became one of the most famous dinosaurs. Brontosaurus has often been depicted in cinema, beginning with Winsor McCay's 1914 classic Gertie the Dinosaur, one of the first animated films. McCay based his unidentified dinosaur on the apatosaurine skeleton in the American Museum of Natural History. The 1925 silent film The Lost World featured a battle between a Brontosaurus and an Allosaurus, using by Willis O'Brien. The 1933 film King Kong featured a Brontosaurus chasing Carl Denham, Jack Driscoll and the terrified sailors on Skull Island. In 1938 the assembling of a Brontosaurus skeleton was a major plot point in the Katharine Hepburn and Cary Grant film Bringing Up Baby. These, and other early uses of the animal as a major representative of the group, helped cement Brontosaurus as a quintessential dinosaur in the public consciousness.
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