Brachiosauridae

The Brachiosauridae are composed of quadrupedal dinosaurs that are generally very large, Evidence for this precision shearing consists of apical wear facets on the teeth and distinctive bone structure that suggests orthal, vertical jaw action. It has been proposed that sauropods possessed a four-chambered double pump heart, with one pump for oxygenated and one pump for deoxygenated blood. As in all Macronaria, the forelimbs of brachiosaurids are long relative to the hindlimbs, but this trait is more pronounced in brachiosaurids. The forelimbs were very slender for a sauropod and the metacarpal bones of the forelimb were elongated. These adaptations overall increased the stride length of the forelimbs, arguably resulting in an uneven gait. However, it was previously argued that they were hindlimb dominant like other sauropods, and thus had the ability to rear up on their hindlimbs. Based on the structure of their legs, making it impossible for them to run, it is likely that they moved about in a low walking speed, 20–40 km/day (12-25 mi/day), but they were capable of moving faster when necessary, up to , depending on leg length. Brachiosaurids shared synapomorphies, new traits typical for the group. They possessed middle and rear back vertebrae with long, 'rod-like' transverse processes. In the pelvis, the ischium had a shortened pubic peduncle, the contact surface with the pubic bone. Their humeri, upper arm bones, had a large deltopectoral crest. Their skull roofs showed wide supratemporal fenestrae, openings for the muscles. They had neural arches placed more on front of the vertebrae, shoulder blades that were expanded at the top end, irregularly shaped coracoids in the shoulder girdle, and triangular projections on the underside of the front branch of their quadratojugal bones at the lower rear corner of the skull. == History of findings ==

Changing classifications In 1903, Elmer Samuel Riggs described and named Brachiosaurus. In 1904, he created a new sauropod family, the Brachiosauridae. He published a complete description of the phenotype after examining the humerus, femur, coracoid and sacrum of the Brachiosaurus holotype that had been prepared at the Field Columbian Museum. Marsh's multifamily theory of sauropod classification prevailed until 1929, when Werner Janensch proposed a two-family theory based on differences in sauropod teeth. This specimen represents the oldest undisputed record of the brachiosaurid group. The following diagram is a timeline of important brachiosaurid discoveries, the date given being that of the naming of the genus. The actual excavation was often much earlier, in the case of Vouivria eighty-three years and of Duriatitan at least 136 years. 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value:rgb(0.999999,0.999999,0) id:pliocene value:rgb(0.97,0.98,0.68) id:quaternary value:rgb(0.98,0.98,0.5) id:pleistocene value:rgb(0.999999,0.95,0.68) id:holocene value:rgb(0.999,0.95,0.88) BarData= bar:eratop bar:space bar:periodtop bar:space bar:NAM1 bar:NAM2 bar:NAM3 bar:NAM4 bar:NAM5 bar:NAM6 bar:NAM7 bar:NAM8 bar:NAM9 bar:NAM10 bar:space bar:period bar:space bar:era PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 shift:(7,-4) bar:periodtop from: 1824 till: 1830 color:1800syears text:20s from: 1830 till: 1840 color:1800syears text:30s from: 1840 till: 1850 color:1800syears text:40s from: 1850 till: 1860 color:1800syears text:50s from: 1860 till: 1870 color:1800syears text:60s from: 1870 till: 1880 color:1800syears text:70s from: 1880 till: 1890 color:1800syears text:80s from: 1890 till: 1900 color:1800syears text:90s from: 1900 till: 1910 color:1900syears text:00s from: 1910 till: 1920 color:1900syears text:10s from: 1920 till: 1930 color:1900syears 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mark:(line,white) width:5 anchor:till align:left color:1900s bar:NAM7 at:2006 mark:(line,black) text:Europasaurus color:1900s bar:NAM1 at:1988 mark:(line,black) text:Giraffatitan color:1900s bar:NAM1 at:1903 mark:(line,black) text:Brachiosaurus color:1900s bar:NAM8 at:2010 mark:(line,black) text:Abydosaurus color:1900s bar:NAM3 at:1999 mark:(line,black) text:Cedarosaurus color:1800s bar:NAM4 at:2001 mark:(line,black) text:Venenosaurus color:1900s bar:NAM5 at:2003 mark:(line,black) text:Lusotitan color:1900s bar:NAM9 at:2010 mark:(line,black) text:Duriatitan color:1800s bar:NAM6 at:2005 mark:(line,black) text:Daanosaurus color:1800s bar:NAM2 at:1998 mark:(line,black) text:Sonorasaurus color:1900s bar:NAM10 at:2017 mark:(line,black) text:Vouivria PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 bar:period from: 1824 till: 1830 color:1800syears text:20s from: 1830 till: 1840 color:1800syears text:30s from: 1840 till: 1850 color:1800syears text:40s from: 1850 till: 1860 color:1800syears text:50s from: 1860 till: 1870 color:1800syears text:60s from: 1870 till: 1880 color:1800syears text:70s from: 1880 till: 1890 color:1800syears text:80s from: 1890 till: 1900 color:1800syears text:90s from: 1900 till: 1910 color:1900syears text:00s from: 1910 till: 1920 color:1900syears text:10s from: 1920 till: 1930 color:1900syears text:20s from: 1930 till: 1940 color:1900syears text:30s from: 1940 till: 1950 color:1900syears text:40s from: 1950 till: 1960 color:1900syears text:50s from: 1960 till: 1970 color:1900syears text:60s from: 1970 till: 1980 color:1900syears text:70s from: 1980 till: 1990 color:1900syears text:80s from: 1990 till: 2000 color:1900syears text:90s from: 2000 till: 2010 color:2000syears text:00s from: 2010 till: 2020 color:2000syears text:10s from: 2020 till: 2030 color:2000syears text:20s from: 2030 till: 2040 color:2000syears text:30s from: 2040 till: 2050 color:2000syears text:40s from: 2050 till: 2060 color:2000syears text:50s from: 2060 till: 2070 color:2000syears text:60s from: 2070 till: 2080 color:2000syears text:70s from: 2080 till: 2090 color:2000syears text:80s from: 2090 till: 2100 color:2000syears text:90s bar:era from: 1824 till: 1900 color:1800s text:19th from: 1900 till: 2000 color:1900s text:20th from: 2000 till: 2100 color:2000s text:21st == Paleo biogeographic distribution ==

'' skeleton from the Tendaguru Formation Definitive brachiosaurid remains have been found from the Late Jurassic period to the Early Cretaceous, from about 157 to 100 million years ago. In addition, Macronaria in general first appear in the Late Jurassic. However, the almost simultaneous appearance of Camarasaurus, Brachiosaurus and a possible titanosaur suggest that they originated earlier, closer to the Middle Jurassic. Trackway evidence also supports a Middle Jurassic origin for titanosaurs, which implies the same for all neosauropods. Brachiosaurids in particular have a broad distribution dating to the Late Jurassic. Late Jurassic specimens have been discovered in the northern and southern Hemispheres, including North America, Africa, Europe and South America. This suggests that brachiosaurids originated in the Middle Jurassic, prior to the breakup of Pangaea, followed by diversification and dispersal that resulted in the global spread present in the Late Jurassic. This conclusion is further supported by paleogeographic data. While many Late Jurassic dinosaur remains have been found in China, no brachiosaurid remains have been uncovered in East Asia. This would support the Middle Jurassic origin theory since East Asia was separated from the rest of Pangaea by water from the late Middle Jurassic to the Early Cretaceous. While brachiosaurids were widely dispersed in the Late Jurassic, their geographic distribution narrowed in the Early Cretaceous. So far, brachiosaurid specimens have only been found in the Aptian–Albian region of North America. This reduction in distribution occurs immediately following the Jurassic–Cretaceous boundary. The brachiosaurid distribution in the Early Cretaceous has been interpreted as a result of regional extinctions in Europe, Africa and South America. Overall, the Early Cretaceous seems to be a time of reduced sauropod diversity worldwide. It has been argued that this change may be due to an extinction event at the Jurassic–Cretaceous boundary. A second hypothesis is that the apparent lack of geographical diversity is due to sampling bias in the generally poor Early Cretaceous fossil record. Recently discovered evidence supports the conclusion that brachiosaurids existed outside of North America in lower latitudes of Gondwana in the Early Cretaceous. In 2013, Mannion et al. reported on the discovery of two isolated teeth found in Lebanon from the Early Cretaceous that possess posteriorly twisted crowns, which are characteristic of the brachiosaurids Giraffatitan and Abydosaurus. In addition, a brachiosaurid named Padillasaurus leivaensis was discovered in Colombia from the Early Cretaceous and placed in the Brachiosauridae taxon, which suggests that Brachiosauridae survived in northwestern Gondwana after the Jurassic/Cretaceous boundary. In the Early Cretaceous, Colombia was located close to the equator in northwestern Gondwana while Lebanon was in the northeast of Gondwana. This suggests that brachiosaurids were in fact present outside of North America in the Early Cretaceous, and supports the theory that the apparent lack of specimens is due to an incomplete record. However, the rarity of these dinosaur specimens may also reflect a decrease in abundance of brachiosaurids acting in combination with the poor fossil record. Also, in 2017 a study indicated that Padillasaurus was not a brachiosaurid but a basal member of the Somphospondyli. ==Classification==

Brachiosauridae is one of the two major clades of Titanosauriformes, a diverse group of sauropods that existed in the Late Jurassic and Cretaceous in Laurasia and Gondwana. Europasaurus is considered the most basal brachiosaurid. }} Cladogram of Brachiosauridae after Mannion et al. (2017) }} ==References==