Brachiosaurus
Brachiosaurus | |
---|---|
Reconstructed replica of the holotype skeleton outside the Field Museum of Natural History | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | †Sauropodomorpha |
Clade: | †Sauropoda |
Clade: | †Macronaria |
Clade: | † Titanosauriformes
|
Family: | †Brachiosauridae |
Genus: | †Brachiosaurus Riggs, 1903 |
Species: | †B. altithorax
|
Binomial name | |
†Brachiosaurus altithorax Riggs, 1903
|
Brachiosaurus (
Brachiosaurus is the namesake genus of the
The
History of discovery
Holotype specimen
The genus Brachiosaurus is based on a partial
Riggs and company were working in the area as a result of favorable correspondence between Riggs and Stanton Merill Bradbury, a dentist in nearby
The site, Riggs Quarry 13, is located on a small hill later known as Riggs Hill; it is today marked by a plaque. More Brachiosaurus fossils are reported on Riggs Hill, but other fossil finds on the hill have been vandalized.[9][11] During excavation of the specimen, Riggs misidentified the humerus as a deformed femur due to its great length, and this seemed to be confirmed when an equally-sized, well-preserved real 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.[12] The excavation attracted large numbers of visitors, delaying the work and forcing Menke to guard the site to prevent bones from being looted. On August 17, the last bone was jacketed in plaster.[13] 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 5,700 kilograms (12,500 lb).[14] On September 10, 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.[15]
The holotype skeleton 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 several ribs.[4][5][16] Riggs described the coracoid as from the left side of the body,[4][12][16] but restudy has shown it to be a right coracoid.[5] 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 downward. 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 embedded in fine-grained clay, indicating low-energy conditions at the time of deposition, it was cut off at the seventh presacral 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.[12]
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.[16] In 1903, he named the type species Brachiosaurus altithorax.[4] 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.[4] The specific epithet was chosen because of the unusually deep and wide chest cavity, from Latin altus "deep" and Greek thorax/θώραξ, "breastplate, cuirass, corslet".[17] Latin thorax was derived from the Greek and had become a usual scientific designation for the chest of the body. The titles of Riggs's 1901 and 1903 articles emphasized that the specimen was the "largest-known dinosaur".[4][16] Riggs followed his 1903 publication with a more detailed description in a monograph in 1904.[12]
Preparation of the holotype began in the fall of 1900 shortly after it was collected by Riggs for the Field Museum. First the limb elements were processed. In the winter of 1904, the badly weathered vertebrae of the back and hip were prepared by James B. Abbott and C.T. Kline.
Assigned material
Further discoveries of Brachiosaurus material in North America have been uncommon and consist of a few bones. To date, material can be unambiguously ascribed only to the genus when overlapping with the holotype material, and any referrals of elements form the skull, neck, anterior dorsal region, or distal limbs or feet remain tentative. Nevertheless, material has been described from Colorado,[5][23][24][25] Oklahoma,[5][26] Utah,[5][23] and Wyoming,[5][27] and undescribed material has been mentioned from several other sites.[3][5]
In 1883, farmer Marshall Parker Felch, a
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
In 1998 Carpenter and Tidwell described the Felch Quarry skull, and formally assigned it to Brachiosaurus sp. (of uncertain species), since it is impossible to determine whether it belonged to the species B. altithorax itself (as there is no overlapping material between the two specimens). They based the skull's assignment to Brachiosaurus on its similarity to that of B. brancai, later known as Giraffatitan.
A shoulder blade with coracoid from
Several additional specimens were briefly described by Jensen in 1987.[23] One of these finds, the humerus USNM 21903, was discovered in ca. 1943 by uranium prospectors Vivian and Daniel Jones in the Potter Creek Quarry in western Colorado, and donated to the Smithsonian Institution. Originally, this humerus was part of a poorly preserved partial skeleton that was not collected.[5][23][37] According to Taylor in 2009, it is not clearly referable to Brachiosaurus despite its large size of 2.13 meters (6 ft 11+3⁄4 in). Jensen himself worked at the Potter Creek site in 1971 and 1975, excavating the disarticulated specimen BYU 4744, which contains a mid-dorsal vertebra, an incomplete left ilium, a left radius and a right metacarpal. According to Taylor in 2009, this specimen can be confidently referred to B. altithorax, as far as it is overlapping with its type specimen. Jensen further mentioned a specimen discovered near Jensen, Utah, that includes a rib 2.75 meters (9 ft 1⁄4 in) in length, an anterior cervical vertebra, part of a scapula, and a coracoid, although he did not provide a description.[5][23] In 2001, Curtice and Stadtman ascribed two articulated dorsal vertebrae (specimen BYU 13023) from Dry Mesa Quarry to Brachiosaurus.[25] Taylor, in 2009, noted that these vertebrae are markedly shorter than those of the B. altithorax holotype, although otherwise being similar.[5]
In 2012, José Carballido and colleagues reported a nearly complete postcranial skeleton of a small juvenile approximately 2 meters (6 ft 7 in) in length. This specimen, nicknamed "Toni" and cataloged as SMA 0009, stems from the Morrison Formation of the
Formerly assigned species
Brachiosaurus brancai and Brachiosaurus fraasi
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, German paleontologist Werner Janensch listed 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.[40] In three further publications in 1929,[41] 1950[42] and 1961,[43] Janensch compared the species in more detail, listing thirteen shared characters between Brachiosaurus brancai (which he now considered to include B. fraasi) and B. altithorax.[5] Taylor, in 2009, considered only four of these characters as valid; six pertain to groups more inclusive than the Brachiosauridae, and the rest are either difficult to assess or refer to material that is not Brachiosaurus.[5]
There was ample material referred to B. brancai in the collections of the Museum für Naturkunde in Berlin, some of which was destroyed during
Janensch based his description of B. brancai on "Skelett S" (skeleton S) from Tendaguru,
In 1988 Gregory S. Paul published a new reconstruction of the skeleton of B. brancai, highlighting differences in proportion between it and B. altithorax. Chief among them was a distinction in the way the trunk vertebrae vary: they are fairly uniform in length in the African material, but vary widely in B. altithorax. Paul believed that the limb and girdle elements of both species were very similar, and therefore suggested they be separated not at genus, but only at subgenus level, as Brachiosaurus (Brachiosaurus) altithorax and Brachiosaurus (Giraffatitan) brancai.[47] Giraffatitan was raised to full genus level by George Olshevsky in 1991, while referring to the vertebral variation.[36] Between 1991 and 2009, the name Giraffatitan was almost completely disregarded by other researchers.[5]
A detailed 2009 study by Taylor of all material, including the limb and girdle bones, found that there are significant divergences between B. 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 between Diplodocus and Barosaurus, and therefore argued that the African material should indeed be placed in its own genus (Giraffatitan) as Giraffatitan brancai.[5] An important contrast between the two genera is their overall body shape, with Brachiosaurus having a 23 percent longer dorsal vertebral series and a 20 to 25 percent longer and also taller tail.[5] The split was rejected by Daniel Chure in 2010,[48] but from 2012 onward most studies recognized the name Giraffatitan.[49]
Brachiosaurus atalaiensis
In 1947, at Atalaia in Portugal, brachiosaurid remains were found in layers dating from the
Brachiosaurus nougaredi
In 1958 French petroleum geologist F. Nougarède reported to have discovered fragmentary brachiosaurid remains in eastern
The type material moved to Paris consisted of a sacrum, weathered out at the desert surface, and some of the left metacarpals and
B. nougaredi was in 2004 considered to represent a distinct, unnamed brachiosaurid genus,
Description
Size
Most estimates of Brachiosaurus altithorax's size are based on the related
While the limb bones of the most complete Giraffatitan skeleton (MB.R.2181) were very similar in size to those of the Brachiosaurus type specimen, the former was somewhat lighter than the Brachiosaurus specimen given its proportional differences. In studies including estimates for both genera, Giraffatitan was estimated at 31.5 metric tons (34.7 short tons),[45][47] 39.5 metric tons (43.5 short tons),[62] 38.0 metric tons (41.9 short tons),[63] 23.3 metric tons (25.7 short tons),[5] and 34.0 metric tons (37.5 short tons).[57] As with the main Brachiosaurus specimen, Giraffatitan specimen MB.R.2181 likely does not reflect the maximum size of the genus, as a fibula (specimen HM XV2) is thirteen percent longer than that of MB.R.2181.[5]
General build
Like all sauropod dinosaurs, Brachiosaurus was a quadruped with a small skull, a long neck, a large trunk with a high-
Brachiosaurus and Giraffatitan probably had a small shoulder hump between the third and fifth
Brachiosaurus differed in its body proportions from the closely related Giraffatitan. The trunk was about 25 to 30 percent longer, resulting in a dorsal vertebral column longer than the humerus. Only a single complete
Postcranial skeleton
Though the vertebral column of the trunk or torso is incompletely known, the back of Brachiosaurus most likely comprised twelve dorsal vertebrae; this can be inferred from the complete dorsal vertebral column preserved in an unnamed brachiosaurid specimen,
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 back sides, the neural spines featured large, triangular and rugose surfaces, which in Giraffatitan were semicircular and much smaller. The various vertebral processes were connected by thin sheets or ridges of bone, which are 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 spines to the diapophyses, were conflated with the spinopostzygapophyseal laminae, which stretched between the neural spines and the
Air sacs not only invaded the vertebrae but also the ribs. In Brachiosaurus, the air sacs invaded through a small opening on the front side of the rib shafts, 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 questioned by Taylor in 2009.
As in Giraffatitan, this vertebra was slightly amphicoelous (concave on both ends), lacked openings on the sides, and had a short neural spine that was rectangular and tilted backward. In contrast to the second caudal vertebra of Giraffatitan, that of Brachiosaurus had a proportionally taller neural arch, making the vertebra about thirty percent taller. The centrum lacked depressions on its sides, in contrast to Giraffatitan. In front or back view, the neural spine broadened toward its tip to approximately three times its minimum width, but no broadening is apparent in Giraffatitan. The neural spines were also inclined backward by about 30 degrees, more than in Giraffatitan (20 degrees). The caudal ribs projected laterally and were not tilted backward as in Giraffatitan. The articular facets of the articular processes at the back of the vertebra were directed downward, while those of Giraffatitan faced more toward 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.[5]
The coracoid was semicircular and taller than broad. Differences from Giraffatitan are related to its shape in side view, including the straighter suture with the scapula. Moreover, the articular surface that forms part of the shoulder joint was thicker and directed more sideward than in Giraffatitan and other sauropods, possibly indicating a more sprawled forelimb. The humerus, as preserved, measures 204 centimeters (80+1⁄2 in) in length, though part of its lower end was 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+1⁄4 in) in width at its narrowest part. It was, however, more robust than that of Giraffatitan, being about ten percent broader at the upper and lower ends. At its upper end, it featured a low bulge visible in side view, which is absent in Giraffatitan.[5]
Distinguishing features can also be found in the
Skull
As reconstructed by Carpenter and Tidwell, the assigned Felch Quarry skull was about 81 centimeters (32 in) long from the
The dorsal and
The premaxilla appears to have been longer than that of Camarasaurus, sloping more gradually toward the nasal bar, which created the very long snout. Brachiosaurus had a long and deep
Each maxilla had space for fourteen or fifteen teeth, whereas Giraffatitan had eleven and Camarasaurus eight to ten. The maxillae contained
Classification
Riggs, in his preliminary 1903 description of the not yet fully prepared holotype specimen, considered Brachiosaurus to be an obvious member of the Sauropoda. To determine the validity of the genus, he compared it to the previously named genera Camarasaurus, Apatosaurus, Atlantosaurus, and Amphicoelias, whose validity he questioned given the lack of overlapping fossil material. Because of the uncertain relationships of these genera, little could be said about the relationships of Brachiosaurus itself.[4] In 1904, Riggs described the holotype material of Brachiosaurus in more detail, especially the vertebrae. He admitted that he originally had assumed a close affinity with Camarasaurus, but now decided that Brachiosaurus was more closely related to Haplocanthosaurus. Both genera shared a single line of neural spines on the back and had wide hips. Riggs considered the differences from other taxa significant enough to name a separate family, Brachiosauridae, of which Brachiosaurus is the namesake genus. According to Riggs, Haplocanthosaurus was the more primitive genus of the family while Brachiosaurus was a specialized form.[12]
When describing Brachiosaurus brancai and B. fraasi in 1914, Janensch observed that the unique elongation of the humerus was shared by all three Brachiosaurus species as well as the British Pelorosaurus. He also noted this feature in Cetiosaurus, where it was not as strongly pronounced as in Brachiosaurus and Pelorosaurus.[40] Janensch concluded that the four genera must have been closely related to each other, and in 1929 assigned them to a subfamily Brachiosaurinae within the family Bothrosauropodidae.[41]
During the twentieth century, several sauropods were assigned to Brachiosauridae, including Astrodon,
Many cladistic analyses have since suggested that at least some genera can be assigned to the Brachiosauridae, and that this group is a basal branch within the Titanosauriformes.[78] The exact status of each potential brachiosaurid varies from study to study. For example, a 2010 study by Chure and colleagues recognized Abydosaurus as a brachiosaurid together with Brachiosaurus, which in this study included B. brancai.[48] In 2009, Taylor noted multiple anatomical differences between the two Brachiosaurus species, and consequently moved B. brancai into its own genus, Giraffatitan. In contrast to earlier studies, Taylor treated both genera as distinct units in a cladistic analysis, finding them to be sister groups. Another 2010 analysis focusing on possible Asian brachiosaurid material found a clade including Abydosaurus, Brachiosaurus, Cedarosaurus, Giraffatitan, and Paluxysaurus, but not Qiaowanlong, the putative Asian brachiosaurid.[78] Several subsequent analyses have found Brachiosaurus and Giraffatitan not to be sister groups, but instead located at different positions on the evolutionary tree. A 2012 study by D'Emic placed Giraffatitan in a more basal position, in an earlier branch, than Brachiosaurus,[75] while a 2013 study by Philip Mannion and colleagues had it the other way around.[49]
This cladogram follows that published by Michael D. D'Emic in 2012:[75]
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Cladistic analyses also allow scientists to determine which new traits the members of a group have in common, their synapomorphies. According to the 2009 study by Taylor, B. altithorax shares with other brachiosaurids the classic trait of having an upper arm bone that is at least nearly as long as the femur (ratio of humerus length to femur length of at least 0.9). Another shared character is the very flattened femur shaft, its transverse width being at least 1.85 times the width measured from front to rear.[5]
Paleobiology
Habits
It was believed throughout the nineteenth and early twentieth centuries that sauropods like Brachiosaurus were too massive to support their own weight on dry land, and instead lived partly submerged in water.
Neck posture
Ongoing debate revolves around the neck posture of brachiosaurids, with estimates ranging from near-vertical to horizontal orientations.[82] The idea of near-vertical postures in sauropods in general was popular until 1999, when Stevens and Parrish argued that the sauropod neck was not flexible enough to be held in an upright, S-curved pose, and instead was held horizontally.[69][83] Reflecting this research, various newspapers ran stories criticizing the Field Museum Brachiosaurus mount for having an upward curving neck. Museum paleontologists Olivier Rieppel and Christopher Brochu defended the posture in 1999, noting the long forelimbs and upward sloping backbone. They also stated that the most developed neural spines for muscle attachment being positioned in the region of the shoulder girdle would have permitted the neck to be raised in a giraffe-like posture. Furthermore, such a pose would have required less energy than lowering its neck, and the inter-vertebral discs would not have been able to counter the pressure caused by a lowered head for extended periods of time (though lowering its neck to drink must have been possible).[84] Some recent studies also advocated a more upward directed neck. Christian and Dzemski (2007) estimated that the middle part of the neck in Giraffatitan was inclined by sixty to seventy degrees; a horizontal posture could be maintained only for short periods of time.[67]
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).[85] The distance between head and heart would have been reduced by the S-curvature of the neck by more than 2 meters (6+1⁄2 ft) in comparison to a totally vertical posture. The neck may also have been lowered during locomotion by twenty degrees.[67] 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 while feeding.[67][86]
Feeding and diet
Brachiosaurus is thought to have been a high
As Brachiosaurus shared its
It has been suggested that Brachiosaurus could rear on its hind legs to feed, using its tail for extra ground support.[47] 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 its 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 only 33 percent more feeding height, compared to other sauropods, for which rearing may have tripled the feeding height.[93] A bipedal stance might have been adopted by Brachiosaurus in exceptional situations, like male dominance fights.[94]
The downward mobility of the neck of Brachiosaurus would have allowed it to reach open water at the level of its feet, while standing upright. Modern giraffes spread their forelimbs to lower the mouth in a relatively horizontal position, to more easily gulp down the water. It is unlikely that Brachiosaurus could have attained a stable posture this way, forcing the animal to plunge the snout almost vertically into the surface of a lake or stream. This would have submerged its fleshy nostrils if they were located at the tip of the snout as Witmer hypothesized. Hallett and Wedel therefore in 2016 rejected his interpretation and suggested that they were in fact placed at the top of the head, above the bony nostrils, as traditionally thought. The nostrils might have evolved their retracted position to allow the animal to breathe while drinking.[95]
Nostril function
The bony nasal openings of
Czerkas speculated on the function of the peculiar brachiosaurid nose, and pointed out that there was no conclusive way to determine where the nostrils where located, unless a head with skin impressions was found. He suggested that the expanded nasal opening would have made room for tissue related to the animal's ability to smell, which would have helped smell proper vegetation. He also noted that in modern reptiles, the presence of bulbous, enlarged, and uplifted nasal bones can be correlated with fleshy horns and knobby protuberances, and that Brachiosaurus and other sauropods with large noses could have had ornamental nasal crests.[81]
It has been proposed that sauropods, including Brachiosaurus, may have had proboscises (trunks) based on the position of the bony narial orifice, to increase their upward reach. Fabien Knoll and colleagues disputed this for Diplodocus and Camarasaurus in 2006, finding that the opening for the facial nerve in the braincase was small. The facial nerve was thus not enlarged as in elephants, where it is involved in operating the sophisticated musculature of the proboscis. However, Knoll and colleagues also noted that the facial nerve for Giraffatitan was larger, and could therefore not discard the possibility of a proboscis in this genus.[97]
Metabolism
Like other sauropods, Brachiosaurus was probably
Air sacs
The
In sauropods, the air sacs did not simply function as an aid for respiration; by means of air channels they were connected to much of the skeleton. These branches, the diverticula, via pneumatic openings invaded many bones and strongly hollowed them out. It is not entirely clear what the evolutionary benefit of this phenomenon was but in any case it considerably lightened the skeleton. They might also have removed excess heat to aid thermoregulation.[99]
In 2016, Mark Hallett and Mathew Wedel for the first time reconstructed the entire air sac system of a sauropod, using B. altithorax as an example of how such a structure might have been formed. In their reconstruction a large abdominal air sac was located between the pelvis and the outer lung side. As with birds, three smaller sacs assisted the pumping process from the underside of the breast cavity: at the rear the posterior thoracic air sac, in the middle the anterior thoracic air sac and in front the clavicular air sac, in that order gradually diminishing in size. The cervical air sac was positioned under the shoulder blade, on top of the front lung. The air sacs were via tubes connected with the vertebrae. Diverticula filled the various fossae and pleurocoels that formed depressions in the vertebral bone walls. These were again connected with inflexible air cells inside the bones.[99]
Growth
The ontogeny of Brachiosaurus has been reconstructed by Carballido and colleagues in 2012 based on Toni (SMA 0009), a postcranial skeleton of a young juvenile with an estimated total body length of just 2 meters (6.6 ft). This skeleton shares some unique traits with the B. altithorax holotype, indicating it is referable to this species. These commonalities 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. There are also differences; these might indicate that the juvenile is not a B. altithorax individual after all, but belongs to a new species. Alternatively, they might be explained as juvenile traits that would have changed when the animal matured.[100]
Such ontogenetic 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: it is 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
Another plausible ontogenetic change is the increased
Two traits are not so obviously linked to ontogeny. The neural spines of the rear dorsal vertebrae and the front sacral vertebrae are extremely compressed transversely, 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 toward each diapophysis, the transverse process bearing the contact facet for the upper rib head, is totally lacking. Both traits could be
Sauropods were likely able to sexually reproduce before they attained their maximum individual size. The maturation rate differed between species. Its bone structure indicates that Brachiosaurus was able to reproduce when it reached forty percent of its maximal size.[101]
Paleoecology
Brachiosaurus is known only from the Morrison Formation of western North America (following the reassignment of the African species).
Other dinosaurs known from the Morrison Formation include the predatory
Cultural significance
Riggs in the first instance tried to limit public awareness of the find. When reading a lecture to the inhabitants of Grand Junction, illustrated by lantern slides, on July 27, 1901, he explained the general evolution of dinosaurs and the exploration methods of museum field crews but did not mention that he had just found a spectacular specimen.[110] He feared that teams of other institutions might soon learn of the discovery and take away the best of the remaining fossils. A week later, his host Bradbury published an article in the local Grand Junction News announcing the find of one of the largest dinosaurs ever. On August 14, The New York Times brought the story.[111] At the time sauropod dinosaurs appealed to the public because of their great size, often exaggerated by sensationalist newspapers.[112] Riggs in his publications played into this by emphasizing the enormous magnitude of Brachiosaurus.[113]
Brachiosaurus has been called one of the most iconic dinosaurs, but most popular depictions are based on the African species B. brancai which has since been moved to its own genus,
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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, ISBN 978-0226074726
- Hallett, M.; Wedel, M. (2016), The Sauropod Dinosaurs: Life in the Age of Giants, Baltimore: Johns Hopkins University Press, ISBN 978-1421420288
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 Brachiosaurus and the concept of holotypes