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Brachiosaurus

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Brachiosaurus
Temporal range: Late Jurassic, 154–153 Ma
FMNH Brachiosaurus.JPG
Reconstructed replica of the holotype skeleton outside the Field Museum of Natural History
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Sauropodomorpha
Clade: Sauropoda
Family: Brachiosauridae
Genus: Brachiosaurus
Riggs, 1903[1]
Species: B. altithorax
Binomial name
Brachiosaurus altithorax
Riggs, 1903[1]

Brachiosaurus /ˌbrækiəˈsɔːrəs/ is a genus of sauropod dinosaur from the Jurassic Morrison Formation of North America. It was first described by American paleontologist Elmer S. Riggs in 1903 from fossils found in the Grand River Canyon (now Colorado River) of western Colorado, in the United States. Riggs named the dinosaur Brachiosaurus altithorax, declaring it "the largest known dinosaur". Brachiosaurus had a disproportionately long neck, small skull, and large overall size, all of which are typical for sauropods. However, the proportions of Brachiosaurus are unlike most sauropods: the forelimbs were longer than the hindlimbs, which resulted in a steeply inclined trunk, and its tail was shorter in proportion to its neck than other sauropods of the Jurassic.

Brachiosaurus is the namesake genus of the family Brachiosauridae, which includes a handful of other similar sauropods. Much of what is known by laypeople about Brachiosaurus is in fact based on Giraffatitan brancai, a species of brachiosaurid dinosaur from the Tendaguru Formation of Tanzania that was originally described by German paleontologist Werner Janensch as a species of Brachiosaurus. Recent research shows that the differences between the type species of Brachiosaurus and the Tendaguru material are significant enough that the African material should be placed in a separate genus. Several other potential species of Brachiosaurus have been described from Africa and Europe, but none of them are thought to belong to Brachiosaurus at this time.

Brachiosaurus is one of the rarer sauropods of the Morrison Formation. The type specimen of B. altithorax is still the most complete specimen, and only a relative handful of other specimens are thought to belong to the genus. It is regarded as a high browser, probably cropping or nipping vegetation as high as possibly 9 metres (30 ft) off of the ground. Unlike other sauropods, and its depiction in the film Jurassic Park, it was unsuited for rearing on its hindlimbs. It has been used as an example of a dinosaur that was most likely ectothermic because of its large size and the corresponding need for sufficient forage, but more recent research finds it to have been warm-blooded.

Description

Size

Size compared to a human

Since "Brachiosaurus" brancai (Giraffatitan) is known from much more complete material than Brachiosaurus altithorax, most size estimates that have been made for Brachiosaurus are actually about the African taxon. There is an additional element of uncertainty for the North American Brachiosaurus because the type (and most complete) specimen appears to represent a subadult, as indicated by the unfused suture between the coracoid and shoulder blade.[2] Over the years, the mass of B. altithorax has been estimated at 35.0 metric tons (38.6 short tons),[3] 43.9 metric tons (48.4 short tons),[4] 28.7 metric tons (31.6 short tons)[2] and, most recently, 56.3 metric tons (62.1 short tons).[5] The length of Brachiosaurus has been estimated at 26 meters (85 ft).[6]

While the limb bones of the most complete Giraffatitan skeleton (MB.R.2181[7]) were very similar in size to those of the Brachiosaurus type specimen, the former specimen was found to be somewhat lighter than the Brachiosaurus specimen given its proportional differences. In studies including estimates for both Brachiosaurus and Giraffatitan, the latter was estimated at 31.5 metric tons (34.7 short tons) by Gregory S. Paul in 1988,[3] 39.5 metric tons (43.5 short tons) by Gerardo Mazzetta and colleagues in 2004,[8] 23.3 metric tons (25.7 short tons) by Michael P. Taylor in 2009,[2] and 34.0 metric tons (37.5 short tons) by Roger Benson and colleagues in 2014.[5] Both the Brachiosaurus type specimen and Giraffatitan specimen MB.R.2181, however, likely do not represent the maximum size reached by these genera—while the Brachiosaurus type specimen was probably not fully grown, a fibula referable to Giraffatitan, specimen HM XV2, was with a length of 134 centimetres found to have been 13% longer than that of MB.R.2181.[2]

General build

Life restoration

Like all sauropod dinosaurs, Brachiosaurus was a quadrupedal animal with a small skull, a long neck, a large trunk with a high-ellipsoid cross section, a long, muscular tail and slender, columnar limbs.[9] Large air sacs connected to the lung system were present in the neck and trunk, invading the vertebrae and ribs, greatly reducing the overall density.[10][11] While the holotype does not include elements of the neck, that of the closely related Giraffatitan was very long even for sauropod standards, consisting of thirteen elongated cervical vertebrae.[12] Brachiosaurus likely shared the very elongated neck ribs with Giraffatitan, which run down the underside of the neck, overlapping several other vertebrae. These bony rods were attached to neck muscles at their ends, allowing these muscles to operate distal portions of the neck while themselves being located closer to the body, thus lightening the neck.[13][14] The ribcage was unusually deep.[1] Although the humerus (upper arm bone) and femur (thigh bone) were roughly equal in length, the entire forelimb would have been longer than the hindlimb, as can be inferred from the elongated forearm and metacarpus known from other brachiosaurids.[2] This lead to the trunk being inclined, with the front much higher than the hips, and the neck exiting the trunk at a steep angle. Overall, this shape resembles a giraffe more than any other living animal.[3] In contrast, most other sauropods show a shorter forelimb than hindlimb; the forelimb is especially short in diplodocoids.[15]

Brachiosaurus differed in its overall body proportions from the closely related Giraffatitan. The trunk was about 25–30% longer than in the latter genus given its more elongated dorsal (back) vertebrae, resulting in a dorsal vertebral column longer than the humerus. Only a single complete caudal (tail) vertebra had been discovered, but its great height indicates that the tail was taller than in Giraffatitan. Furthermore, this vertebra showed a much greater area for ligament attachment due to the broadened neural spine, indicating that the tail was also longer than in the African taxon, possibly by 20–25%.[2] Although Paul, in 1988, suggested that the neck was shorter with Brachiosaurus than in Giraffatitan, two cervical vertebrae likely belonging to Brachiosaurus suggest identical proportions.[2][3] Unlike Giraffatitan and other sauropods, which showed vertically oriented forelimbs, the arm of Brachiosaurus appears to have been slightly sprawled at the shoulder joint, as indicated by the sidewards orientation of the joint surface of the coracoid.[2] The humerus was less slender than that of Giraffatitan, while the femur showed similar proportions. This might indicate that the forelimbs of Brachiosaurus supported a greater fraction of the body weight than is the case for Giraffatitan.[2]

Postcranial skeleton

Fifth back vertebra in front of the pelvis of the holotype, compared to a human back vertebral column

Although the vertebral column of the trunk is incompletely known, Brachiosaurus most likely possessed twelve dorsal vertebrae, as can be inferred from the complete dorsal vertebral column preserved by an unnamed brachiosaurid specimen, BMNH R5937, in 1930 collected in the Tendaguru by Frederick William Hugh Migeod.[16] Vertebrae of the front part of the dorsal column were slightly taller but much longer than those of the back part. This is in contrast to Giraffatitan, where the vertebrae of the front part were only slightly longer but much taller. The centra (vertebral bodies), which form the lower part of the vertebrae, were more elongated than in Giraffatitan and roughly circular in cross-section, while those of the latter genus were broader than tall in cross-section. The small openings (foramina) on the sides of the centra, which allowed for the intrusion of air sacs, were larger than in Giraffatitan. The diapophyses (large projections extending sideways from the neural arch of the vertebrae) were horizontal, while those of Giraffatitan were inclined upwards. At their ends, these processes articulated with the ribs; the articular surface was not distinctly triangular as in Giraffatitan. The upwards projecting neural spines, when seen in side view, stand vertically and were twice as wide at the base than at the top, while those of Giraffatitan were tilted backwards and were not broadened at their base. When seen in front or back view, the neural spines widened towards their tops. In Brachiosaurus, this widening occurred gradually, resulting in a paddle-like shape, while in Giraffatitan the widening occurred abruptly and only in the uppermost portion. At both their front and the back side, the neural spine showed large, triangular rugose surfaces, which are semicircular and much smaller in Giraffatitan. The various processes were connected by thin sheets of bone, the so-called laminae. Brachiosaurus lacked postspinal laminae, which were present in Giraffatitan, running down the back side of the neural spines. The spinodiapophyseal laminae, which stretched from the neural spine to the diapophyses, was conflated with the spinopostzygapophyseal laminae, which stretched between the neural spines and the articular process at the back of the vertebra, and therefore terminated at mid-height of the neural spine. In Giraffatitan, both laminae were not conflated, and the spinodiapophyseal laminae reached up to the top of the neural spine. Three further details of the laminae of the dorsal vertebrae are only known from Giraffatitan, and are absent in other sauropods including Brachiosaurus, adding to the features distinguishing these genera.[2]

Sixth back vertebra in front of the pelvis

Air sacs did not only invade the vertebrae, but also the ribs. In Brachiosaurus, the air sac invaded through a small opening on the front side of the rib shaft, while in Giraffatitan openings were present on both the front and back sides of the tuberculum, a bony projection articulating with the diapophyses of the vertebrae. Paul, in 1988, stated that the ribs of Brachiosaurus were longer than in Giraffatitan, which was however questioned by Taylor in 2009.[2] Behind the dorsal vertebral column, the sacrum consisted of five co-ossified sacral vertebrae.[17] As in Giraffatitan, the sacrum was proportionally broad and featured very short neural spines. Poor preservation of the sacral material in Giraffatitan however precludes detailed comparisons between both genera. Of the tail, only the second caudal vertebra is well preserved. As in Giraffatitan, this vertebra was slightly amphicoelous (concave on both ends), lacked lateral openings, and possessed a short neural spine that was rectangular and tilted backwards. In contrast to the second caudal vertebra of Giraffatitan, that of Brachiosaurus showed a proportionally taller neural arch, making the vertebra ca. 30% taller. The centrum showed no depressions at its sides, in contrast to Giraffatitan. In front or back view, the neural spine broadened towards its tip to approximately three times its minimum width. In Giraffatitan, in contrast, no widening is apparent. The neural spines is also inclined backwards by about 30°, more than in Giraffatitan (20°). The caudal ribs project laterally and were not tilted backwards as in Giraffatitan. The articular facets of the articular processes at the back of the vertebra were directed more downwards, while those of Giraffatitan faced more towards the sides. Besides the articular processes, the hyposphene-hypantrum articulation formed an additional articulation between vertebrae, making the vertebral column more rigid; in Brachiosaurus, the hyposphene was much more pronounced than in Giraffatitan.[2]

Femur and humerus of the holotype in 1905

The coracoid, a bone of the shoulder girdle that forms part of the shoulder joint, was semicircular and taller than broad. Differences to Giraffatitan are related to its shape in side view, including the straighter suture between the coracoid and the scapula (shoulder blade). Moreover, the articular surface forming the shoulder joint was thicker and directed more sidewards than in Giraffatitan and other sauropods, possibly indicating a more sprawled forelimb. The humerus, as preserved, measures 204 centimeters (80 in) in total length, although part of its lower end are lost to erosion; its original length is estimated at 216 centimeters (85 in). This bone was more slender in Brachiosaurus than in most other sauropods, measuring only 28.5 centimeters (11.2 in) in width at its narrowest part. It was, however, more robust than that of Giraffatitan, being around 10% broader at both the upper and lower ends. At its upper end, it featured a low bulge visible in side view, which is absent in Giraffatitan. Distinguishing features can also be found in the ilium of the pelvis. In Brachiosaurus, the ischiadic peduncle, a downwards projecting extension connecting to the ischium, reaches farther downwards than in Giraffatitan. While the latter genus shows a sharp notch between the ischiadic peduncle and the back portion of the ilium, this notch is more rounded in Brachiosaurus. On the upper surface of the hind part of the bone, Brachiosaurus showed a pronounced tubercle that is absent in other sauropods. Of the hind limb, the femur was very similar to that of Giraffatitan. As in the latter genus, it was strongly elliptical in cross-section, being more than twice as wide in front or back view than in side view. The femur of Brachiosaurus, however, was slightly more robust than that of Giraffatitan. Further differences include the more prominent and further downwards located fourth trochanter, a bulge serving as the anchor point for the most important locomotory muscle, the caudofemoralis. Furthermore, the condyles at the lower end were not extending backwards as strongly as in Giraffatitan; both condyles were similar in width in Brachiosaurus but unequal in Giraffatitan.[2]

Skull

Reconstruction of the Felch Quarry Brachiosaurus sp. skull, Denver Museum of Nature & Science. The fleshy nostril would have been placed at the front of the demarcated nasal fossa

Though no skull remains were discovered with the original Brachiosaurus skeleton, one partial skull found at a different location, referred to as the Felch Quarry skull (specimen USNM 5730), may belong to Brachiosaurus. Since there is no overlapping material between the two specimens, the skull has only been assigned to B. sp. (of uncertain species). As reconstructed, the skull was about 81 centimeters (2.66 ft) long from the occipital condyle at be the back of the skull to the front of the premaxillae (the front bones of the upper jaw), making it the largest sauropod skull known from the Morrison Formation. It appears to have been most similar to and intermediate between that of Giraffatitan and Camarasaurus. Overall, the skull was tall as in Giraffatitan, with a snout that was long (about 36% of the skull length) in front of the nasal bar between the nostrils, which is typical of brachiosaurids. The snout was set at an angle relative to the rest of the skull, which gave the impression that the snout pointed downwards. The frontal bones on top of the skull were short and wide (similar to Giraffatitan), fused together, and connected by a suture to the parietal bones, which were also fused together. Combined, the frontoparietals were wider than long on the midline, with a suture that extended jaggedly across the skull. The surface of the parietals between the supratemporal fenestrae (openings at the rear skull roof) was wider than that of Giraffatitan, but narrower than that of Camarasaurus. The supratemporal fenestrae were triangular in shape, and almost twice as wide as they were long. The skull differed from that of Giraffatitan in having a U-shaped (instead of W-shaped) suture between the frontal and nasal bones, enhanced by the frontal bones extending forwards over the orbits (eye sockets).[18]

Most of the bones that formed the rear part of the skull were fused together, which obliterated the sutures, apart from that between the parietal and supraoccipital bones. Similar to Giraffatitan, the neck of the occipital condyle was very long. The premaxilla appears to have been longer than that of Camarasaurus, sloping more gradually towards the nasal bar, which created the very long snout. Brachiosaurus had a long and deep maxilla (the main bone of the upper jaw), which was thick along the margin where the alveoli (tooth sockets) were placed, thinning upwards. The interdental plates of the maxilla were thin, fused, porous, and triangular. There were triangular nutrient foramina between the plates, each containing the tip of an erupting tooth. The narial fossa (depression) in front of the bony nostril was long and contained a subnarial fenestra, which was much larger than those of Giraffatitan and Camarasaurus. The dentaries (the bones of the lower jaws that contained the teeth) were robust, though less than in Camarasaurus. The mandibular symphysis (where the two dentaries connected at the front of the mandible) interlocked with a weak tongue and groove. The upper margin of the dentary was arched in profile, but not as much as in Camarasaurus. The interdental plates of the dentary were somewhat oval, with diamond shaped openings between them. The dentary had a Meckelian groove that was open until below the ninth alveolus, continuing thereafter as a shallow through.[18]

Skull cast of the related Giraffatitan, Natural History Museum, Berlin

Each maxilla had space for about 14 or 15 teeth, whereas Giraffatitan had 11 and Camarasaurus 8 to 10. The maxillae contained replacement teeth which showed rugose enamel, similar to Camarasaurus, but lacked the small denticles (serrations) along the edges. Since the maxilla was wider than that of Camarasaurus, Brachiosaurus would have possessed larger teeth. The replacement teeth in the premaxilla had crinkled enamel, and the most complete of these teeth did not have denticles. Each dentary had space for about 14 teeth. The only well preserved tooth of this skull is large, spoon-shaped, and may be from the front part of the left dentary. It differs from those of Giraffatitan in that the crown is much wider than the root, similar to Camarasaurus. That the tooth is not worn implies that it had erupted around the time the animal died. The outer and inner sides of the tooth were crenelated (had indented vertical grooves); the crenelations of one side met with those of the other side at the top of the tooth, where they formed denticles. The maxillary tooth rows of Brachiosaurus and Giraffatitan end well in front of the antorbital fenestra (the opening in front of the orbit), whereas they end just before and below the fenestra in Camarasaurus and Shunosaurus.[18]

Though the bony nasal openings of neosauropods like Brachiosaurus were large and placed on the top of their skulls, the American paleontologist Lawrence M. Witmer pointed out in 2001 that all living vertebrate land animals have their external fleshy nostrils placed to the front of the bony nostril. The fleshy nostrils of such sauropods would have been placed at the front of the narial fossa, the depression which extended far in front of the bony nostril towards the snout. Earlier, the fleshy nostrils of sauropods were thought to have been placed at the back of the bony nostril because these animals were inaccurately thought to have been amphibious, and used their large nasal openings as snorkels when submerged.[19]

History of discovery

The Brachiosaurus holotype

Holotype material during excavation

The genus Brachiosaurus, and type species B. altithorax, are based on a partial postcranial skeleton from Fruita, in the valley of the Colorado River of western Colorado.[20] This specimen was collected from rocks of the Brushy Basin Member of the Morrison Formation[21] in 1900 by American paleontologist Elmer S. Riggs and his crew from the Field Columbian Museum (now the Field Museum of Natural History) of Chicago.[1] It is currently cataloged as FMNH P 25107.[2]

Riggs and company were working in the area as a result of favorable correspondence between Riggs and Stanton Merill Bradbury, a dentist in nearby Grand Junction. In the spring of 1899, Riggs had sent letters to mayors in western Colorado, inquiring after possible trails leading from railway heads into northeastern Utah, where he hoped to find Eocene mammals.[22] To his surprise, he was informed by Bradbury, an amateur collector himself and president of the Western Colorado Academy of Science, that dinosaur bones had been collected near Grand Junction since 1885.[20] Riggs was sceptical of this claim, but his superior, curator of geology Oliver Cummings Farrington, was very eager to add a large sauropod skeleton to the collection, to outdo other institutions, and convinced the museum management to invest five hundred dollars in an expedition.[23] Arriving on 20 June, they set camp at the abandoned Goat Ranch.[24] During a prospect on horse-back, Riggs' field assistant Harold William Menke found the humerus of FMNH P 25107,[1] on July 4, 1900,[25] exclaiming it was "the biggest thing yet!". Riggs at first took the find for a badly preserved Brontosaurus specimen and gave priority to excavating Quarry 12, which held a more promising Morosaurus skeleton. Having secured that, on 26 July he returned to the humerus in Quarry 13, which soon proved to be of enormous size, convincing a puzzled Riggs that he had discovered the largest land animal ever.[26] The site, Riggs Quarry 13, was found on a small hill later known as Riggs Hill; it is marked by a plaque. Additional Brachiosaurus fossils are reported on Riggs Hill, but other fossil finds on the hill have been vandalized.[25][27] During excavation of the specimen, Riggs misidentified the humerus as a deformed femur due to its great length, and found himself confirmed when an equally sized, well-preserved femur of the same skeleton was discovered. In 1904, Riggs noted: "Had it not been for the unusual size of the ribs found associated with it, the specimen would have been discarded as an Apatosaur, too poorly preserved to be of value." It was only after preparation of the fossil material in the laboratory that the bone was recognized as a humerus.[17] The excavation attracted large numbers of visitors, delaying the work and forcing Menke to guard the site to prevent bones from being looted. On 17 August, the last bone was jacketed in plaster.[28] After a concluding ten-day prospecting trip, the expedition returned to Grand Junction and hired a team and wagon to transport all fossils to the railway station, during five days; another week was spent to pack them in thirty-eight crates with a weight of 12,500 pounds.[29] On 10 September, Riggs left for Chicago by train, arriving on the 15th; the railroad companies let both passengers and cargo travel for free, as a public relations gesture.[30]

Elmer S. Riggs’ preparator, H.W. Menke, lying by the humerus during the excavation in 1900

The skeleton (specimen number FMNH P 25107) consists of the right humerus (upper arm bone), the right femur (thigh bone), the right ilium (a hip bone), the right coracoid (a shoulder bone), the sacrum (fused vertebrae of the hip), the last seven thoracic (trunk) and two caudal (tail) vertebrae, and a number of ribs.[1][2][31] Riggs described the coracoid as from the left side of the body,[1][17][31] but restudy has shown it to be a right coracoid.[2] At the time of discovery, the lower end of the humerus, the underside of the sacrum, the ilium and the preserved caudal vertebrae were exposed to the air and thus partly damaged by weathering. The vertebrae were only slightly shifted out of their original anatomical position; they were found with their top sides directed downwards. The ribs, humerus, and coracoid, however, were displaced to the left side of the vertebral column, indicating transportation by a water current. This is further evidenced by an isolated ilium of Diplodocus that apparently had drifted against the vertebral column, as well as by a change in composition of the surrounding rocks. While the specimen itself was imbedded in fine-grained clay, indicating low-energy conditions at the time of deposition, it was cut off at the seventh vertebra by a thick layer of much coarser sediments consisting of pebbles at its base and sandstone further up, indicating deposition under stronger currents. Based on this evidence, Riggs in 1904 suggested that the missing front part of the skeleton was washed away by a water current, while the hind part was already covered by sediment and thus got preserved.[17]

Riggs, on the right, and an assistant working on Brachiosaurus altithorax bones; the still jacketed thighbone can be seen on the left

Riggs published a short report of the new find in 1901, noting the unusual length of the humerus compared to the femur and the extreme overall size and the resulting giraffe-like proportions, as well as the lesser development of the tail, but did not publish a name for the new dinosaur.[31] The titles of Riggs (1901[31]) and (1903[1]) suggested that the specimen was the largest known dinosaur.[1][31] Riggs followed his 1903 publication that named Brachiosaurus altithorax[1] with a more detailed description in a monograph in 1904.[17] Riggs derived the genus name from the Greek brachion/βραχίων meaning "arm" and sauros/σαυρος meaning "lizard", because he realized that the length of the arms was unusual for a sauropod.[1] The species epithet was chosen because of the unusually deep and wide chest cavity, from Latin altus "deep" and Greek thorax/θώραξ (Latin thorax), "breastplate, cuirass, corslet".[32]

Apatosaurus in the Field Columbian Museum (now Field Museum of Natural History) with Brachiosaurus holotype and other dinosaur bones in glass cases in the background, 1909

Preparation of P 25107, the holotype of Brachiosaurus, began in the fall of 1900 shortly after it was collected by Riggs for the Field Museum of Natural History (Chicago). As the preparation of each bone was finished, it was put on display in a glass case in Hall 35 of the Fine Arts Palace of the Worlds Columbian Exposition, Field Museum's first home. All the bones were, solitary, still on display by 1908 in Hall 35 when the Field Museum's newly mounted Apatosaurus was unveiled, the very specimen Riggs had found in Quarry 12,[33] today catalogued as FMNH P25112 and seen as a Brontosaurus exemplar.[34] However, no mount of Brachiosaurus was attempted because only 20% of the skeleton had been recovered. In 1993, the holotype bones were molded and cast, and the missing bones were sculpted based on Giraffatitan material in Berlin. This plastic skeleton was mounted and, in 1994, put on display at the north end of Stanley Field Hall, the main exhibit hall of the Field Museum's current building. The real bones of the holotype were put on exhibit in two large glass cases at either end of the mounted cast. The mount stood until 1999, when it was moved to the B Concourse of United Airlines' Terminal One in O'Hare International Airport to make room for the museum's newly acquired T. rex, "SUE".[35] At the same time, the Field Museum mounted a second plastic cast of the skeleton (designed for outside use) and it has been on display outside the museum on the NW terrace ever since. The only real bones currently on display are the humerus and two dorsals in the Mesozoic Hall of the Field Museum's Evolving Planet exhibit.[36]

In 1969, in a study by R.F. Kingham, Brachiosaurus altithorax, "B." brancai and "B." atalaiensis, along with many species now assigned to other genera, were placed in the genus Astrodon, creating an Astrodon altithorax.[37] Kingham's views of brachiosaurid taxonomy have, however, not been accepted by many authors.[38]

Assigned material

O.C. Marsh's outdated 1891 skeletal reconstruction of Brontosaurus, with skull inaccurately based on that of the Felch Quarry B. sp.

In 1883, farmer Marshall Parker Felch, a fossil collector for the American paleontologist Othniel Charles Marsh, reported the discovery of a sauropod skull in Felch Quarry 1, near Garden Park, Colorado. The skull was found in yellowish white sandstone, near a 1 meter (3.3 ft) long cervical vertebra, which was destroyed during an attempt to collect it. The skull was catalogued as YPM 1986, and sent to Marsh at the Peabody Museum of Natural History, who incorporated it into his 1891 skeletal restoration of Brontosaurus (perhaps because Felch had identified it as belonging to that dinosaur). The Felch Quarry skull consists of the cranium, the maxillae, the right postorbital, part of the left maxilla, the left squamosal, the right quadrate, the dentaries, a possible partial pterygoid, and a front tooth from the dentary. The bones were roughly prepared for Marsh, which lead to some damage. Most of the specimens collected by Felch were sent to the National Museum of Natural History in 1899 after Marsh's death, including the skull, which was then catalogued as USNM 5730.[18][39][40]

In 1975, the American paleontologists Jack McIntosh and David Berman investigated the historical issue of whether Marsh had assigned an incorrect skull to Brontosaurus (at the time thought to be a junior synonym of Apatosaurus), and found the Felch Quarry skull to be of "the general Camarasaurus type", while suggesting that the vertebra found near it belonged to Brachiosaurus. They concluded that if Marsh had not arbitrarily assigned the Felch quarry skull and another Camarasaurus-like skull to Brontosaurus, it would have been recognized earlier that the actual skull of Brontosaurus and Apatosaurus was more similar to that of Diplodocus.[40] McIntosh later tentatively recognized the Felch Quarry skull as belonging to Brachiosaurus, and brought it to the attention of the American paleontologists Kenneth Carpenter and Virginia Tidwell, while urging them to descibe it. They brought the skull to the Denver Museum of Natural History, where they further prepared it and made a reconstruction of it based on casts of the individual bones, with the skulls of Giraffatitan and Camarasaurus acting as templates for the missing bones. In 1998, Carpenter and Tidwell described the Felch Quarry skull, and formally assigned it to B. sp., since it is impossible to determine whether it belonged to the species B. altithorax itself.[18][41]

Scapulocoracoid now assigned to Brachiosaurus, which was originally assigned to Ultrasauros (now a junior synonym of Supersaurus), Museum of Ancient Life

Additional discoveries of Brachiosaurus material in North America have been uncommon and consist of a handful of bones. Material has been described from Colorado,[2][42][43][44] Oklahoma,[2][45] Utah,[2][42] and Wyoming,[2][4] and undescribed material has been mentioned from several other sites.[2][21] One of these specimens, a shoulder blade from Dry Mesa Quarry, Colorado, is one of the specimens at the center of the Supersaurus/Ultrasauros issue of the 1980s and 1990s. In 1985, James A. Jensen described disarticulated sauropod remains from the quarry as belonging to several taxa, including the new genera Supersaurus and Ultrasaurus,[46] the latter renamed Ultrasauros shortly thereafter because another sauropod already had the name.[47] Later study showed that the "ultrasaur" material mostly belonged to Supersaurus, although the shoulder blade did not. Because the holotype of Ultrasauros, a back vertebra, was one of the specimens that was actually from Supersaurus, the name Ultrasauros is a synonym of Supersaurus. The shoulder blade, specimen BYU 9462 (previously BYU 5001), is now assigned to Brachiosaurus, but the species is uncertain.[2][43] In addition, the Dry Mesa "ultrasaur" was not as large as had been thought; the dimensions of the shoulder's coracoid bone indicate that the animal was smaller than Riggs' original specimen of Brachiosaurus.[2]

Referred front limb bone (humerus) from Potter Creek, USNM 21903

Taylor (2009) lists a number of specimens referred to Brachiosaurus. These include some material, e.g. a humerus from Potter Creek and some Dry Mesa material (the latter partly described as Ultrasauros by Jensen), that are either clearly not brachiosaurid in origin, or at least not clearly referable to Brachiosaurus.[2] In contrast, a cervical (neck) vertebra and the skull mentioned above may belong to either B. altithorax or an as-yet unknown brachiosaurid from North America.[2] The cervical was found near Jensen, Utah, by Jensen,[42] and – if it belongs to Brachiosaurus – is one of a handful of neck vertebrae known for American brachiosaurids.[2] There is no unambiguous material of the skull, neck, anterior dorsal (forward trunk) region, distal (lower) limbs or feet.[2] In 2012, José Carballido et al reported on a nearly complete postcranial skeleton of a juvenile sauropod (approximately 2 metres (6.6 ft) long) from the Morrison Formation of the Bighorn Basin, north-central Wyoming. This specimen, SMA 0009 nicknamed "Toni", was originally thought to belong to a diplodocid, but the authors reinterpreted it as representing a brachiosaurid, probably Brachiosaurus altithorax.[48]

Formerly assigned species

B. brancai and B. fraasi

Skeleton of Giraffatitan, formerly B. brancai, Berlin

Between 1909 and 1912, large-scale paleontological expeditions in German East Africa unearthed a considerable amount of brachiosaurid material from the Tendaguru Formation. In 1914, Janensch listed a number of differences and commonalities between these fossils and B. altithorax, concluding they could be referred to the genus Brachiosaurus. From this material Janensch named two species: Brachiosaurus brancai for the larger and more complete taxon, and Brachiosaurus fraasi for the smaller and more poorly known species.[49] In three further publications in 1929,[50] 1950[51] and 1961[52] Janensch compared the species in more detail, listing thirteen putative shared characters between Brachiosaurus brancai (which he now considered to include B. fraasi) and Brachiosaurus altithorax.[2] Of these, however, only four appear to be valid, while six pertain to more inclusive groups than the Brachiosauridae, and the rest are either difficult to assess or refer to material that is not Brachiosaurus.[2]

There was ample material referred to "B." brancai in the collections of the Museum für Naturkunde Berlin, some of which was destroyed during World War II. Other material was transferred to other institutions throughout Germany, some of which was also destroyed. Additional specimens are likely among the material collected by the British Museum of Natural History's Tendaguru expedition.[53] Much or all of this material probably belongs to Giraffatitan, although some may represent a new brachiosaurid.[54]

Janensch based his description of "B." brancai on "Skelett S" (skeleton S) from Tendaguru,[49] but later realized that it comprised two partial individuals: S I and S II.[50] He at first did not designate them as a syntype series, but in 1935 made S I (presently MB.R.2180) the lectotype. Taylor in 2009, unaware of this action, proposed the larger and more complete S II (MB.R.2181) as the lectotype.[2] It includes, among other bones, several dorsal (trunk) vertebrae, the left scapula, both coracoids, both sternals (breastbones), both humeri, both ulna and radii (lower arm bones), a right hand, a partial left hand, both pubes (a hip bone) and the right femur, tibia and fibula (shank bones). Later Taylor realised that Janensch had in 1935 designated the smaller skeleton S I as the lectotype.[7][55]

Diagram incorporating bones of both Brachiosaurus and Giraffatitan, by William Diller Matthew, 1915

In 1988, Gregory S. Paul published a new reconstruction of the skeleton of "B." brancai, highlighting a number of differences in proportion between it and B. altithorax. Chief among them was a difference in the way the trunk vertebrae vary: they are fairly uniform in length in the African material, but differ widely in B. altithorax. Paul believed that the limb and girdle elements of both species were very similar, and therefore suggested to separate them not at genus, but only at subgenus level as a Brachiosaurus (Giraffatitan) brancai.[3] Giraffatitan was raised to genus level by George Olshevsky in 1991, referring to the vertebral variation.[47]

A detailed study of all material, including the limb and girdle bones, by Michael P. Taylor in 2009 found that there are significant differences between Brachiosaurus altithorax and the Tendaguru material in all elements known from both species. Taylor found twenty-six distinct osteological (bone-based) characters, a larger difference than that between e.g. Diplodocus and Barosaurus, and therefore argued that the African material should indeed be placed in its own genus—Giraffatitan—as Giraffatitan brancai.[2] An important difference between the two genera is the overall body shape, with Brachiosaurus having a 23% longer dorsal (trunk) vertebrate series and a 20 to 25% longer and also taller tail.[2]

B. atalaiensis

Originally described by Albert-Félix de Lapparent and Georges Zbyszewski in 1957,[56] "B." atalaiensis' reference to Brachiosaurus was doubted in 2004 by Paul Upchurch, Barret and Dodson,[9] who listed it as an unnamed brachiosaurid, and placed in its own genus Lusotitan by Miguel Telles Antunes and Octávio Mateus.[57] De Lapparent and Zbyszewski described a series of remains but did not designate a type specimen. Antunes and Mateus selected a partial postcranial skeleton (MIGM 4978, 4798, 4801–4810, 4938, 4944, 4950, 4952, 4958, 4964–4966, 4981–4982, 4985, 8807, 8793–87934) as a lectotype; this specimen includes 28 vertebrae, chevrons, ribs, a possible shoulder blade, humeri, forearm bones, partial left pelvis, lower leg bones, and part of the right ankle. The low neural spines, the prominent deltopectoral crest of the humerus (a muscle attachment site on the upper arm bone), the elongated humerus (very long and slender), and the long axis of the ilium tilted upward indicate that Lusotitan is a brachiosaurid.[57]

B. nougaredi

Diagram showing preserved parts of the "B." nougaredi sacrum in blue

The species "B." nougaredi is known from fragmentary remains discovered in eastern Algeria, in the Sahara Desert. The present type material consists of a sacrum and some of the left metacarpals and phalanges. Found at the discovery site but not collected were partial bones of the left forearm, wrist bones, a right shin bone, and fragments that may have come from metatarsals.[58] Albert-Félix de Lapparent, who described and named the material in 1960, reported the discovery locality as being in the Late Jurassic–age Taouratine Series (he assigned the rocks this age in part because of the presumed presence of Brachiosaurus),[58] but more recent review assigns it to the "Continental intercalaire," which is considered to be of Albian age (late Early Cretaceous, significantly younger).[9]

"B." nougaredi was formerly considered to be a species of Brachiosaurus,[58] or a distinct, unnamed brachiosaurid,[9] but a more recent analysis finds that the remains probably belong to more than one species.[59] The metacarpals were found to belong to an indeterminate Titanosauriform. Because the sacrum's current location is unknown, it was not analyzed and considered an indeterminate sauropod until its rediscovery. Only four out of the five sacral vertebrae are preserved, but the preserved portion alone measures 1.3 metres (4.3 ft) long, larger than any other sauropod sacrum ever found, except Argentinosaurus and Apatosaurus.[59]

Classification

Brachiosaurus was originally classified as a generic sauropod by Riggs, as not enough material was known to compare it properly to Camarasaurus, Apatosaurus, or Atlantosaurus.[1] In 1904, Riggs described more of the holotype material of Brachiosaurus, and decided that it was more closely related to Haplocanthosaurus than any other sauropod known from the Morrison Formation. Because of the significant differences from other taxa, Riggs named the family Brachiosauridae, of which Brachiosaurus is the namesake genus.[17] When describing Brachiosaurus brancai and B. fraasi, Janensch noted the slenderness of the humerus was unique to all three Brachiosaurus species and Pelorosaurus. Cetiosaurus was also mentioned to have a more slender humerus, but not as much as in Brachiosaurus or Pelorosaurus.[49] Over the years, a number of sauropods have been assigned to Brachiosauridae, such as Astrodon, Bothriospondylus, Dinodocus, Pelorosaurus, Pleurocoelus, and Ultrasaurus,[60] but most of these are currently regarded as dubious or of uncertain placement.[9] A phylogenetic analysis of sauropods published in the description of Abydosaurus found that genus to form a clade with Brachiosaurus and Giraffatitan (included in Brachiosaurus).[61] A more recent analysis focused on possible Asian brachiosaurid material found a clade including Abydosaurus, Brachiosaurus, Cedarosaurus, Giraffatitan, and Paluxysaurus, but not Qiaowanlong, the putative Asian brachiosaurid.[62] Related genera include Lusotitan and Sauroposeidon.[9] Brachiosauridae is situated at the base of Titanosauriformes, a group of sauropods that also includes the titanosaurs.[62]

Restorations of macronarian sauropods (right to left):Camarasaurus, Brachiosaurus, Giraffatitan and Euhelopus

According to the revised diagnosis by Taylor, Brachiosaurus altithorax is diagnosed by a plethora of characters, many to be found on the dorsal (back) vertebrae.[2] Among the characters placing it in the family Brachiosauridae are a ratio of humerus length to femur length of at least 0.9 (i.e. the upper arm bone is at least nearly as long as the thigh bone), and a very flattened femur shaft (ratio ≥1.85).[2] The cladogram of Brachiosauridae below is after D'Emic (2012).[38]

Brachiosauridae 

Europasaurus




Giraffatitan




Brachiosaurus




Abydosaurus



Cedarosaurus



Venenosaurus






Paleobiology

Assigned neck vertebra, BYU Museum of Paleontology

It was believed throughout the 19th and early 20th centuries that sauropods like Brahiosaurus were too massive to support their own weight on dry land. It was theorized that they lived partly submerged in water. Riggs however, concluded that Brachiosaurus was a fully terrestrial animal and more recent findings have supported this.[63] It is estimated that sauropods could not have breathed through their nostrils when the rest of the body was submerged, as the water pressure on the chest wall would be too great.[64][65] In addition, the hollowness of the bones would have made the sauropods buoyant.[66]

It has been proposed that sauropods, including Brachiosaurus, may have had proboscises based on the position of the bony narial orifice. Kroll et al. (2006) disputed this for Diplodocus and Camrasaurus' finding that the infraorbital foramen (reconstructed from an endocranial cast) was too small. However, they also noted that the facial nerve for Giraffatitan was larger.[67]

Neck posture and movement

Reconstructed skeleton showing the neck pointing upwards, at O'Hare International Airport (formerly housed in the Field Museum)

Historically, reconstructions of the neck positions of Brachiosaurus have varied from fairly low to nearly vertical. More recent studies have favored an upward posture. Unlike other sauropods like Diplodocus and Apatosaurus, which likely held their heads horizontally, Brachiosaurus and its kin had front limbs which were longer than the hind limbs; elevating the shoulder above the level of the pelvis and giving them a vertebrate that slops upward.[68][69] Studies by Christian and Heinrich (1998), Christian (2002) and Christian and Dzemski (2007) examined the compressive forces on the interlocking joints of the cervical vertebrate of Giraffatitan and concluded that they were consistent with the animal habitually holding its head more vertically with its center of mass located above the base of the neck. The angle between the horizontal plane and the middle part of the neck was estimated to have been 60–70 degrees. In addition, the neck likely formed an S-shape most of the time. Brachiosaurids could have adapted a more horizontal posture but only for short periods of time.[13][70][71]

With their heads held high above the heart, brachiosaurids would have had stressed cardiovascular systems. It is estimated that the heart of Brachiosaurus would have to pump double the blood pressure of a giraffe to reach the brain, and possibly weighed 400 kg (880 lb).[68] However, an S-curvature of the neck could have reduced distance between the brain and heart by 2 m (6 ft 7 in) in comparison to a totally vertical posture. In addition, the head and neck may have been lowered during locomotion.[13] The flexibility of the neck of sauropods has been debated. Mobility was reconstructed as quite low by Stevens and Parrish.[72][73][74] while other researchers like Paul and Christian and Dzemski argued for more flexible necks.[3][75] In studying the inner ear of Giraffatitan, Gunga & Kirsch (2001) concluded that brachiosaurids would have moved their necks in lateral directions more often than in dorsal-ventral directions.[13][76]

Feeding and diet

Closeup of the teeth of airport reconstruction

Brachiosaurus is thought to have been a high browser, feeding on foliage well above the ground. Even if it did not hold its neck near vertical, and instead had a straighter neck, its head height may still have been over 9 metres (30 ft) above the ground.[4][77] It probably fed mostly on foliage above 5 metres (16 ft). This does not preclude the possibility that it also fed lower at times, between 3 to 5 metres (9.8 to 16.4 ft) up.[77] Its diet likely consisted of ginkgos, conifers, tree ferns, and large cycads, with intake estimated at 200 to 400 kilograms (440 to 880 lb) of plant matter daily.[77] However, more recent studies estimate that ~240 kilograms (530 lb) of plant matter would have been sufficient to feed a 70 metric tons (77 short tons) sauropod,[78] so Brachiosaurus may have required only about 120 kilograms (260 lb) of fodder a day. Brachiosaur feeding involved simple up–and–down jaw motion. The teeth were arranged to shear material as they closed, and were probably used to crop and/or nip vegetation.[79]

It has been suggested that Brachiosaurus could rear into a bipedal or tripodal (with tail support) pose to feed.[3] However, a detailed physical modelling-based analysis of sauropod rearing capabilities by Heinrich Mallison showed that while many sauropods could rear, the unusual body shape and limb length ratio of brachiosaurids made them exceptionally ill suited for rearing. The forward position of the center of mass would have led to problems with stability, and required unreasonably large forces in the hips to obtain an upright posture. Brachiosaurus would also have gained relatively little from rearing (only 33% more feeding height), compared to other sauropods, for which a bipedal pose may have tripled the feeding height.[80]

Metabolism

Like all sauropods, Brachiosaurus was homeothermic (maintaining a stable internal temperature) and endothermic (controlling body temperature through internal means), meaning that it was able to actively control its body temperature ("warm-blooded"), producing the necessary heat through a high basic metabolic rate of its cells.[81] In the past, Brachiosaurus has been used an example of a dinosaur for which endothermy is unlikely, because of the combination of great size (leading to overheating) and great caloric needs to fuel endothermy.[82] However, these calculations were based on incorrect assumptions about the available cooling surfaces (the large air sacs were not known), and a grossly inflated body mass. These inaccuracies resulted in the overestimation of heat production and the underestimation of heat loss.[81] The large nasal arch has been postulated as an adaptation for cooling the brain, as a surface for evaporative cooling of the blood.[82]

Growth

Mounted reconstruction of SMA 0009, possibly a juvenile Brachiosaurus

The ontogeny of Brachiosaurus has been reconstructed by Carballido et al. (2012) based on SMA 0009, a postcranial skeleton. This specimen represents a quite young juvenile with an estimated total body length of just two metres. It shares some unique traits with the Brachiosaurus altithorax holotype, indicating it is referable to this species. These include an elevation on the rear blade of the ilium; the lack of a postspinal lamina; vertical neural spines on the back; an ilium with a subtle notch between the appendage for the ischium and the rear blade; and the lack of a side bulge on the upper thighbone. However, there are also differences. These might indicate that the juvenile is not a B. altithorax individual after all, but belongs to a species new to science. Alternatively, they might be explained as juvenile traits that would have changed when the animal matured.[83]

Such changes are especially to be expected in the proportions of an organism. The middle neck vertebrae of SMA 0009 are remarkably short for a sauropod, being just 1.8 times longer than high, compared with a ratio of 4.5 in Giraffatitan. This suggests that the necks of brachiosaurids became proportionally much longer while their backs, to the contrary, experienced relative negative growth. The humerus of SMA 0009 is relatively robust: more slender than that of most basal titanosauriforms but thicker than the upper arm bone of B. altithorax. This suggests that it was already lengthening in an early juvenile stage and became even more slender during growth. This is in contrast to diplodocoids and basal macronarians, whose slender humeri are not due to such allometric growth. Brachiosaurus also appears to have experienced an elongation of the metacarpals, which in juveniles were shorter compared to the length of the radius. SMA 0009 shows a ratio of just 0.33, the lowest known in the entire Neosauropoda.[83]

Another plausible ontogenetic development is the increased pneumatisation of the vertebrae. During growth, the diverticula of the air sacs invaded the bones and hollowed them out. SMA 0009 already has pleurocoels, pneumatic excavations, at the sides of its neck vertebrae. These are divided by a ridge but are otherwise still very simple in structure, compared with the extremely complex ridge systems typically shown by adult derived sauropods. Its back vertebrae still completely lack such pleurocoels.[83]

Two traits are not so obviously linked to ontogeny. The neural spines of the rear back vertebrae and the front sacral vertebrae are extremely transversely compressed, being eight times longer from front to rear than wide from side to side. The spinodiapophyseal lamina or "SPOL", the ridge normally running from each side of the neural spine towards each diapophysis, the transverse process bearing the contact facet for the upper rib head, is totally lacking. Both traits could be autapomorphies, unique derived characters proving that SMA 0009 represents a distinct species. However, there are indications that these traits are growth-related as well. Of the basal sauropod Tazoudasaurus a young juvenile is known that also lacks the spinodiapophyseal lamina, whereas the adult form has an incipient ridge. A very young juvenile of Europasaurus shows a weak SPOL but it is well developed in mature individuals. These two cases represent the only finds in which the condition can be checked; they suggest that the SPOL developed during growth. As this very ridge widens the neural spine, its transverse compression is not an independent trait and the development of the SPOL plausibly precedes the thickening of the neural spine with more mature animals.[83]

Paleoecology

Juvenile B. sp. specimen SMA 0009 (the skull is reconstructed), Sauriermuseum Aathal

With the removal of the East African Giraffatitan, Brachiosaurus is known only from the Morrison Formation of western North America.[2] The Morrison Formation is interpreted as a semiarid environment with distinct wet and dry seasons,[84][85] and flat floodplains.[84] Vegetation varied from gallery forests (river–lining forests in otherwise treeless settings) of conifers, tree ferns, and ferns, to fern savannas with rare Araucaria-like trees.[86] Several other sauropod genera were present in the Morrison Formation, with differing body proportions and feeding adaptations.[4] Among these were Apatosaurus, Barosaurus, Camarasaurus, Diplodocus, Haplocanthosaurus, and Supersaurus.[4][87] Brachiosaurus was one of the less abundant Morrison Formation sauropods. In a survey of over 200 fossil localities, John Foster reported 12 specimens of the genus, comparable to Barosaurus (13) and Haplocanthosaurus (12), but far fewer than Apatosaurus (112), Camarasaurus (179), and Diplodocus (98).[4] Brachiosaurus fossils are found only in the lower-middle part of the expansive Morrison Formation (stratigraphic zones 2–4), dated to about 154-153 million years ago,[88] unlike many other types of sauropod which have been found throughout the formation.[4]

The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs.[89] Other dinosaurs known from the Morrison include the theropods Koparion, Stokesosaurus, Ornitholestes, Ceratosaurus, Allosaurus and Torvosaurus, the sauropods Apatosaurus, Camarasaurus, and Diplodocus, and the ornithischians Camptosaurus, Dryosaurus, Othnielia, Gargoyleosaurus and Stegosaurus.[90] Diplodocus is commonly found at the same sites as Apatosaurus, Allosaurus, Camarasaurus, and Stegosaurus.[91] Allosaurus, which accounting for 70 to 75% of theropod specimens and was at the top trophic level of the Morrison food web.[92] Many of the dinosaurs of the Morrison Formation are the same genera as those seen in Portuguese rocks of the Lourinha Formation (mainly Allosaurus, Ceratosaurus, Torvosaurus, and Stegosaurus), or have a close counterpart (Brachiosaurus and Lusotitan, Camptosaurus and Draconyx).[93] Other vertebrates that shared this paleoenvironment included ray-finned fishes, frogs, salamanders, turtles like Dorsetochelys, sphenodonts, lizards, terrestrial and aquatic crocodylomorphans such as Hoplosuchus, and several species of pterosaur like Harpactognathus and Mesadactylus. Shells of bivalves and aquatic snails are also common. 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.[94]

Cultural significance

Brachiosaurus is today one of the best-known dinosaurs amongst both paleontologists and the general public. Its iconic status however, is largely based on the African species B. brancai which has been given its own generic name Giraffatitan.[2]

A main belt asteroid, 1991 GX7, has been named 9954 Brachiosaurus in honor of the genus.[95][96] The genus has been featured in many films and television programs, most notably the Jurassic Park and Walking with Dinosaurs series. The digital model of Brachiosaurus used in Jurassic Park went on to become the starting point for the ronto models in the 1997 special edition of the science fiction film Star Wars Episode IV: A New Hope.[97]

References

  1. ^ a b c d e f g h i j k l Riggs, E.S. (1903). "Brachiosaurus altithorax, the largest known dinosaur". American Journal of Science. 4. 15 (88): 299–306. doi:10.2475/ajs.s4-15.88.299. 
  2. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj Taylor, M.P. (2009). "A re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropoda) and its generic separation from Giraffatitan brancai (Janensh 1914)" (PDF). Journal of Vertebrate Paleontology. 29 (3): 787–806. doi:10.1671/039.029.0309. 
  3. ^ a b c d e f g Paul, G.S. (1988). "The brachiosaur giants of the Morrison and Tendaguru with a description of a new subgenus, Giraffatitan, and a comparison of the world's largest dinosaurs" (pdf). Hunteria. 2 (3). 
  4. ^ a b c d e f g Foster, J.R. (2003). Paleoecological analysis of the vertebrate fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain region, U.S.A. New Mexico Museum of Natural History and Science Bulletin, 23. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. 
  5. ^ a b Benson, R. B. J.; Campione, N. S. E.; Carrano, M. T.; Mannion, P. D.; Sullivan, C.; Upchurch, P.; Evans, D. C. (2014). "Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem Lineage". PLoS Biology. 12 (5): e1001853. doi:10.1371/journal.pbio.1001853. PMC 4011683Freely accessible. PMID 24802911. 
  6. ^ Holtz, Thomas R. Jr. (2008) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages Supplementary Information
  7. ^ a b Taylor, M.P. (2011). "Correction: A re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropoda) and its generic separation from Giraffatitan brancai (Janensch 1914)"". Journal of Vertebrate Paleontology. 31 (3): 727. doi:10.1080/02724634.2011.557115. 
  8. ^ Mazzetta, G.V.; Christiansen, P.; Farina, R.A. (2004). "Giants and Bizarres: Body Size of Some Southern South American Cretaceous Dinosaurs". Historical Biology. 16 (2–4): 1–13. doi:10.1080/08912960410001715132. 
  9. ^ a b c d e f Upchurch, P.; Barrett, P.M.; Dodson, P. (2004). "Sauropoda". In Weishampel, D.B.; Dodson, P.; Osmolska, H. The Dinosauria, Second Edition. University of California Press, Berkeley. pp. 259–322. ISBN 978-0-520-24209-8. 
  10. ^ Wedel, M.J. (2003). "Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs". Paleobiology. 29 (2): 243–255. doi:10.1666/0094-8373(2003)029<0243:vpasat>2.0.co;2. 
  11. ^ Wedel, M.J. (2003). "The evolution of vertebral pneumaticity in sauropod dinosaurs". Journal of Vertebrate Paleontology. 23 (2): 344–357. doi:10.1671/0272-4634(2003)023[0344:teovpi]2.0.co;2. 
  12. ^ Taylor, Michael P.; Wedel, Mathew J. (2013). "Why sauropods had long necks; and why giraffes have short necks". PeerJ. 1: –36. 
  13. ^ a b c d Christian, A.; Dzemski, G. (2007). "Reconstruction of the cervical skeleton posture of Brachiosaurus brancai Janensch, 1914 by an analysis of the intervertebral stress along the neck and a comparison with the results of different approaches" (PDF). Fossil Record. 10 (1): 38–49. doi:10.1002/mmng.200600017. 
  14. ^ Klein, Nicole; Christian, Andreas; Sander, P. Martin (2012). "Histology shows that elongated neck ribs in sauropod dinosaurs are ossified tendons". Biology Letters: –20120778. 
  15. ^ Carrano, Matthew T. (2005). "The Evolution of Sauropod Locomotion". In Christina Curry Rogers, Jeffrey Wilson (eds.). The sauropods: evolution and paleobiology. Oakland, California: University of California Press. pp. 229–251. 
  16. ^ Migeod, F.W.H. (1931). "British Museum East Africa Expedition: Account of the work done in 1930". Natural History Magazine. 3: 87–103. 
  17. ^ a b c d e f Riggs, E.S. (1904). "Structure and relationships of opisthocoelian dinosaurs. Part II. The Brachiosauridae". Geological Series (Field Columbian Museum). 2 (6): 229–247. 
  18. ^ a b c d e Carpenter, K.; Tidwell, V. (1998). "Preliminary description of a Brachiosaurus skull from Felch Quarry 1, Garden Park, Colorado". Modern Geology. 23 (1–4): 69–84. 
  19. ^ Witmer, L. M. (2001). "Nostril position in dinosaurs and other vertebrates and its significance for nasal function". Science. 293 (5531): 850–853. doi:10.1126/science.1062681. PMID 11486085. 
  20. ^ a b Glut, D.F. (1997). "Brachiosaurus". Dinosaurs: The Encyclopedia. McFarland & Company. pp. 213–221. ISBN 978-0-89950-917-4. 
  21. ^ a b Turner, C.E.; Peterson, F. (1999). "Biostratigraphy of dinosaurs in the Upper Jurassic Morrison Formation of the Western Interior, USA". In Gillete, David D. Vertebrate Paleontology in Utah. Miscellaneous Publication 99-1. Salt Lake City, Utah: Utah Geological Survey. pp. 77–114. ISBN 978-1-55791-634-1. 
  22. ^ Brinkman 2010, p. 106.
  23. ^ Brinkman 2010, p. 105.
  24. ^ Brinkman 2010, p. 108.
  25. ^ a b Chenoweth, W.L. (1987). "The Riggs Hill and Dinosaur Hill sites, Mesa County, Colorado". In Averett, Walter R. Paleontology and Geology of the Dinosaur Triangle. Grand Junction, Colorado: Museum of Western Colorado. pp. 97–100. ISBN 978-9-99979-041-3. LCCN 93247073. OCLC 680488874. 
  26. ^ Brinkman 2010, p. 111.
  27. ^ Lohman, S.W. (1965). Geology and artesian water supply of the Grand Junction area, Colorado. Professional Paper 451. Reston, Virginia: U.S. Geological Survey. pp. 1–149. 
  28. ^ Brinkman 2010, p. 117.
  29. ^ Brinkman 2010, p. 118.
  30. ^ Brinkman 2010, p. 119.
  31. ^ a b c d e Riggs, E.S. (1901). "The largest known dinosaur". Science. 13 (327): 549–550. Bibcode:1901Sci....13..549R. doi:10.1126/science.13.327.549-a. PMID 17801098. 
  32. ^ Liddell, H.G.; Scott, R. "θώραξ". A Greek-English Lexicon. Perseus Digital Library. Retrieved 2018-04-06. 
  33. ^ Brinkman 2010, p. 243.
  34. ^ Tschopp, E.; Mateus, O.V.; Benson, R.B.J. (2015). "A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda)". PeerJ. 3: e857. doi:10.7717/peerj.857. PMC 4393826Freely accessible. PMID 25870766. 
  35. ^ "Expect Awe-Struck Travelers" (Press release). The Field Museum. 1999-11-26. Retrieved 2009-08-27. [dead link]
  36. ^ "Captions from Selected Historical Photographs (caption number GN89396_52c)" (PDF). The Field Museum Photo Archives. Retrieved 2009-08-27. [dead link]
  37. ^ Kingham, R.F. (1962). "Studies of the sauropod dinosaur Astrodon Leidy". Proceedings of the Washington Junior Academy of Sciences. 1: 38–44. 
  38. ^ a b D'Emic, M. D. (2012). "The early evolution of titanosauriform sauropod dinosaurs". Zoological Journal of the Linnean Society. 166 (3): 624–671. doi:10.1111/j.1096-3642.2012.00853.x. 
  39. ^ Marsh, O.C. (1891). "Restoration of Triceratops" (pdf). American Journal of Science. 41 (244): 339–342. doi:10.2475/ajs.s3-41.244.339. 
  40. ^ a b McIntosh, J.S.; Berman, D.S. (1975). "Description of the palate and lower jaw of the sauropod dinosaur Diplodocus (Reptilia: Saurischia) with remarks on the nature of the skull of Apatosaurus". Journal of Paleontology. 49 (1): 187–199. JSTOR 1303324. 
  41. ^ Tidwell, V. (1996). "Restoring crushed Jurassic dinosaur skulls for display". In Morales, M. The Continental Jurassic: Transactions of the Continental Jurassic Symposium. 60. Museum of Northern Arizona Bulletin. 
  42. ^ a b c Jensen, J.A. (1987). "New brachiosaur material from the Late Jurassic of Utah and Colorado". The Great Basin Naturalist. 47 (4): 592–608. 
  43. ^ a b Curtice, B.; Stadtman, K.; Curtice, L. (1996). "A re-assessment of Ultrasauros macintoshi (Jensen, 1985)". In Morales, M. The Continental Jurassic: Transactions of the Continental Jurassic Symposium. 60. Museum of Northern Arizona Bulletin. pp. 87–95. 
  44. ^ Curtice, B.; Stadtman, K. (2001). "The demise of Dystylosaurus edwini and a revision of Supersaurus vivianae". In McCord, R.D.; Boaz, D. Western Association of Vertebrate Paleontologists and Southwest Paleontological Symposium – Proceedings 2001. 8. Mesa Southwest Museum Bulletin. pp. 33–40. 
  45. ^ Bonnan, M.F.; Wedel, M.J. (2004). "First occurrence of Brachiosaurus (Dinosauria, Sauropoda) from the Upper Jurassic Morrison Formation of Oklahoma" (PDF). PaleoBios. 24 (2): 12–21. 
  46. ^ Jensen, J.A. (1985). "Three new sauropod dinosaurs from the Upper Jurassic of Colorado". The Great Basin Naturalist. 45 (4): 697–709. 
  47. ^ a b Olshevsky, G. (1991). "A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia" (PDF). Mesozoic Meanderings. 2: 1–196. 
  48. ^ Carballido, J.L.; Marpmann, J.S.; Schwarz-Wings, D.; Pabst, B. (2012). "New information on a juvenile sauropod specimen from the Morrison Formation and the reassessment of its systematic position". Palaeontology. 55 (2): 567–582. doi:10.1111/j.1475-4983.2012.01139.x. 
  49. ^ a b c Janensch, W (1914). "Übersicht über der Wirbeltierfauna der Tendaguru-Schichten nebst einer kurzen Charakterisierung der neu aufgefuhrten Arten von Sauropoden" [Overview of the vertebrate fauna of the Tendaguru strata along with a brief characterization of the newly listed species of sauropods] (PDF). Archiv für Biontologie (in German). 3: 81–110. 
  50. ^ a b Janensch, W. (1929). "Material und Formengehalt der Sauropoden in der Ausbeute der Tendaguru-Expedition." Palaeontographica (Suppl. 7) 2:1–34.
  51. ^ Janensch, W. (1950). "Die Wirbelsäule von Brachiosaurus brancai". Palaeontographica (Suppl. 7). 3: 27–93. 
  52. ^ Janensch, W. (1961). "Die Gliedmaßen und Gliedmaßengürtel der Sauropoden der Tendaguru-Schichten". Palaeontographica (Suppl. 7). 3: 177–235. 
  53. ^ Maier, G. (2003). African dinosaurs unearthed: The Tendaguru Expeditions. Bloomington, IN: Indiana University Press. ISBN 978-0-253-34214-0. 
  54. ^ Taylor, M. "CT-scanning the Archbishop". Sauropod Vertebrate Picture of the Week. Retrieved 2009-11-18. 
  55. ^ Janensch, W. (1936). "Die Schädel der Sauropoden Brachiosaurus, Barosaurus und Dicraeosaurus aus den Tendaguru-Schichten Deutsch-Ostafrikas" [The skulls of the sauropods Brachiosaurus, Barosaurus and Dicraeosaurus from the Tendaguru layers of German East Africa] (PDF). Palaeontographica (in German). 2: 147–298. 
  56. ^ de Lapparent, A.F.; Zbyszewski, G. (1957). "Les dinosauriens du Portugal" (PDF). Mémoire Service géologique Portugal. 2: 1–63. 
  57. ^ a b Antunes, M.; Mateus, O. (2003). "Dinosaurs of Portugal". Comptes Rendus Palevol. 2 (1): 77–95. doi:10.1016/S1631-0683(03)00003-4. 
  58. ^ a b c de Lapparent, A.F. (1960): "Les dinosauriens du "continental intercalaire" du Sahara central" ("The dinosaurs of the "continental intercalaire" of the central Sahara.") Mémoires de la Société Géologic de France, Nouvelle Série 88A vol.39(1–6):1–57. [in French; a translated version, by Matthew Carrano (pdf, no figures), is available through the Polyglot Paleontologist]
  59. ^ a b Mannion, Philip D.; Upchurch, Paul; Barnes, Rosie N.; Mateus, Octávio (2013). "Osteology of the Late Jurassic Portuguese sauropod dinosaur Lusotitan atalaiensis (Macronaria) and the evolutionary history of basal titanosauriforms" (PDF). Zoological Journal of the Linnean Society. 168: 98–206. doi:10.1111/zoj.12029. 
  60. ^ Lambert, David; the Diagram Group (1990). "Brachiosaurids". The Dinosaur Data Book. New York: Avon Books. p. 142. ISBN 978-0-380-75896-8. 
  61. ^ Chure, D.; Britt, B.; Whitlock, J. A.; Wilson, J. A. (2010). "First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition" (PDF). Naturwissenschaften. 97 (4): 379–391. Bibcode:2010NW.....97..379C. doi:10.1007/s00114-010-0650-6. PMC 2841758Freely accessible. PMID 20179896. 
  62. ^ a b Ksepka, D. T.; Norell, M. A. (2010). "The illusory evidence for Asian Brachiosauridae: new material of Erketu ellisoni and a phylogenetic appraisal of basal Titanosauriformes" (pdf). American Museum Novitates. 3700: 1–27. doi:10.1206/3700.2. 
  63. ^ Jensen, J. A. (1985). "Three new sauropod dinosaurs from the Upper Jurassic of Colorado". Great Basin Naturalist. 45 (4): 697–709. 
  64. ^ Pierson, D.J. (2009). "The Physiology of Dinosaurs: Circulatory and Respiratory Function in the Largest Animals Ever to Walk the Earth". Respiratory Care. 54 (7): 887–911. doi:10.4187/002013209793800286. PMID 19558740. 
  65. ^ Kermack, Kenneth A. (1951). "A note on the habits of sauropods". Annals and Magazine of Natural History. 12 (4): 830–832. 
  66. ^ Henderson, D. M. (2004). "Tipsy punters: sauropod dinosaur pneumaticity, buoyancy and aquatic habits". Proceedings of the Royal Society of London B. 271(Suppl 4): S180–S183. doi:10.1098/rsbl.2003.0136. 
  67. ^ Knoll, F.; Galton, P. M.; López-Antoñanzas, R. (2006). "Paleoneurological evidence against a proboscis in the sauropod dinosaur Diplodocus". Geobios. 39: 215–221. doi:10.1016/j.geobios.2004.11.005. 
  68. ^ a b Fastovsky, D. E.; Weishampel, D. B. (2016). Dinosaurs: A Concise Natural History. Cambridge University Press. p. 206. ISBN 978-1107135376. 
  69. ^ Rieppel, O.; C. Brochu (1999). "Paleontologists defend dinosaur mount". In The Field. 70: 8. 
  70. ^ Christian, A.; Heinrich, W-D. (1998). "The Neck Posture of Brachiosaurus brancai" (PDF). Fossil Record. 1 (1): 73–80. doi:10.1002/mmng.19980010105. 
  71. ^ Christian. A. (2002). "Neck posture and overall body design in sauropods" (PDF). Fossil Record. 5 (1): 271–281. doi:10.1002/mmng.20020050116. 
  72. ^ Stevens, K. A.; Parrish, M. J. (1999). "Neck posture and feeding habits of two Jurassic sauropod dinosaurs". Science. 284 (5415): 798–800. Bibcode:1999Sci...284..798S. doi:10.1126/science.284.5415.798. PMID 10221910. 
  73. ^ Stevens, K. A. and Parrish, M. J. (2005). "Digital reconstructions of sauropod dinosaurs and implications for feeding." In The sauropods: evolution and paleobiology (eds. J. A.Wilson & K. Curry-Rogers), pp. 178–200. Berkeley, CA: University of California Press.
  74. ^ Stevens, K. A. and Parrish, M. J. (2005). "Neck posture, dentition and feeding strategies in Jurassic sauropod dinosaurs." In Thunder Lizards: The Sauropodomorph dinosaurs" (eds. V. Tidwell & K. Carpenter). Bloomington, IN: Indiana University Press.
  75. ^ Dzemski, G.; Christian, A. (2007). "Flexibility along the neck of the ostrich (Struthio camelus) and consequences for the reconstruction of dinosaurs with extreme neck length". Journal of Morphology. 268 (8): 701–714. doi:10.1002/jmor.10542. 
  76. ^ Gunga, H.-C.; Kirsch, K. (2001). "Von Hochleistungsherzen und wackeligen Ha¨lsen". Forschung. 2–3: 4–9. 
  77. ^ a b c Foster, J. (2007). "Brachiosaurus altithorax." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 205–208.
  78. ^ Hummel, J.; Gee, C.T.; Südekum, K.-H.; Sander, P.M.; Nogge, G.; Clauss, M. (2008). "In vitro digestibility of fern and gymnosperm foliage: implications for sauropod feeding ecology and diet selection". Proceedings of the Royal Society B. 275 (1638): 1015–1021. doi:10.1098/rspb.2007.1728. PMC 2600911Freely accessible. PMID 18252667. 
  79. ^ Barrett, Paul M.; Upchurch, Paul (2005). "Sauropodomorph diversity through time". In Curry Rogers, Kristina A.; Wilson, Jeffrey A. The Sauropods: Evolution and Paleobiology. Berkeley, CA: University of California. pp. 125–156. ISBN 0520246233. 
  80. ^ Mallison, H. (2011). "Rearing Giants – kinetic-dynamic modeling of sauropod bipedal and tripodal poses." In Klein, N., Remes, K., Gee, C. & Sander M. (eds): Biology of the Sauropod Dinosaurs: Understanding the life of giants. Life of the Past (series ed. Farlow, J.). Bloomington, IN: Indiana University Press.
  81. ^ a b Sander, P.M.; Christian, A.; Clauss, M.; Fechner, R.; Gee, C.T.; Griebeler, E.-M.; Gunga, H.-C.; Hummel, J.; Mallison, H.; Perry, S.F.; Preuschoft, H.; Rauhut, O.W.M.; Remes, K.; Tütken, T.; Wings, O.; Witzel, U. (2010). "Biology of the sauropod dinosaurs: the evolution of gigantism". Biology Reviews. 86 (1): 117–155. doi:10.1111/j.1469-185X.2010.00137.x. PMC 3045712Freely accessible. PMID 21251189. 
  82. ^ a b Russell, D. A. (1989). An Odyssey in Time: Dinosaurs of North America. Minocqua, Wisconsin: NorthWord Press. p. 78. ISBN 978-1-55971-038-1. 
  83. ^ a b c d Carballido, J. L.; Marpmann, J. S.; Schwarz-Wings, D.; Pabst, B. (2012). "New information on a juvenile sauropod specimen from the Morrison Formation and the reassessment of its systematic position". Palaeontology. 55 (3): 567–582. doi:10.1111/j.1475-4983.2012.01139.x. 
  84. ^ a b Russell, D. A. (1989). An Odyssey in Time: Dinosaurs of North America. Minocqua, Wisconsin: NorthWord Press. pp. 64–70. ISBN 978-1-55971-038-1. 
  85. ^ Engelmann, G.F.; Chure, D.J.; Fiorillo, A.R. (2004). "The implications of a dry climate for the paleoecology of the fauna of the Upper Jurassic Morrison Formation". Sedimentary Geology. 167 (3–4): 297–308. Bibcode:2004SedG..167..297E. doi:10.1016/j.sedgeo.2004.01.008. 
  86. ^ Carpenter, K. (2006). "Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus". In Foster, J. R.; Lucas, S. G. Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin, 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 131–138. 
  87. ^ Chure, D.J.; Litwin, R.; Hasiotis, S.T.; Evanoff, E.; Carpenter, K. (2006). "The fauna and flora of the Morrison Formation: 2006". In Foster, J.R.; Lucas, S.G. Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin, 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 233–248. 
  88. ^ Turner, C.E. and Peterson, F., (1999). "Biostratigraphy of dinosaurs in the Upper Jurassic Morrison Formation of the Western Interior, U.S.A." Pp. 77–114 in Gillette, D.D. (ed.), Vertebrate Paleontology in Utah. Utah Geological Survey Miscellaneous Publication 99-1.
  89. ^ Foster, J. (2007). "Appendix." Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327–329.
  90. ^ Chure, Daniel J.; Litwin, Ron; Hasiotis, Stephen T.; Evanoff, Emmett; Carpenter, Kenneth (2006). "The fauna and flora of the Morrison Formation: 2006". In Foster, John R.; Lucas, Spencer G. Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin, 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 233–248. 
  91. ^ Dodson, Peter; Behrensmeyer, A.K.; Bakker, Robert T.; McIntosh, John S. (1980). "Taphonomy and paleoecology of the dinosaur beds of the Jurassic Morrison Formation". Paleobiology. 6 (2): 208–232. 
  92. ^ Foster, John R. (2003). Paleoecological Analysis of the Vertebrate Fauna of the Morrison Formation (Upper Jurassic), Rocky Mountain Region, U.S.A. New Mexico Museum of Natural History and Science Bulletin, 23. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. p. 29. 
  93. ^ Mateus, Octávio (2006). "Jurassic dinosaurs from the Morrison Formation (USA), the Lourinhã and Alcobaça Formations (Portugal), and the Tendaguru Beds (Tanzania): A comparison". In Foster, John R.; Lucas, Spencer G. Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin, 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 223–231. 
  94. ^ Carpenter, Kenneth (2006). "Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus". In Foster, John R.; Lucas, Spencer G. Paleontology and Geology of the Upper Jurassic Morrison Formation. New Mexico Museum of Natural History and Science Bulletin, 36. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 131–138. 
  95. ^ "JPL Small-Body Database Browser: 9954 Brachiosaurus (1991 GX7)". NASA. Retrieved 2007-04-28. 
  96. ^ Williams, G. "Minor Planet Names: Alphabetical List". Smithsonian Astrophysical Observatory. Retrieved 2007-02-10. 
  97. ^ "Ronto". Databank. Star Wars.com. Archived from the original on October 3, 2008. Retrieved 2009-01-13. [better source needed]

Bibliography

  • Brinkman, P. D. (2010), The Second Jurassic Dinosaur Rush: Museums and Paleontology in America at the Turn of the Twentieth Century, Chicago and London: The University of Chicago Press 

External links

  • The dictionary definition of Brachiosaurus at Wiktionary
  • Media related to Brachiosaurus at Wikimedia Commons
  • The First Brachiosaurus – Interview with Joyce Havstad of the Field Museum about Braciosaurus and the concept of holotypes
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