The Brachiosauridae ("arm lizards", from Greek brachion (βραχίων) = "arm" and sauros = "lizard") are a family or clade of herbivorous, quadrupedal sauropod dinosaurs. Brachiosaurids had long necks that enabled them to access the leaves of tall trees that other sauropods would have been unable to reach. In addition, they possessed thick spoon-shaped teeth which helped them to consume tough plants more efficiently than other sauropods. They have also been characterized by a few unique traits or synapomorphies; dorsal vertebrae with 'rod-like' transverse processes and an ischium with an abbreviated pubic peduncle.
Brachiosaurus is one of the best-known members of the Brachiosauridae, and was once thought to be the largest land animal to ever live. Brachiosaurids thrived in the regions which are now North and South America, Africa, Europe, and Asia. They first appear in the fossil record in the Late Jurassic Period and disappear in the late Early Cretaceous Period. The broad distribution of Brachiosauridae in both northern and southern continents suggests that the group originated prior to the breakup of Pangaea. In the Early Cretaceous the distribution of the group is dramatically reduced. It is still unclear whether this reduction is due to local extinctions or to the limited nature of the Early Cretaceous fossil record.
Brachiosauridae has been defined as all titanosauriforms that are more closely related to Brachiosaurus than to Saltasaurus. It is one of the three main groups of the clade Titanosauriformes, which also includes the Euhelopodidae and the Titanosauria.
|Mounted Brachiosaurus skeleton cast, Field Museum of Natural History|
The Brachiosauridae are composed of quadrupedal dinosaurs that are generally very large, with the exception of the possible insular dwarf Europasaurus. The brachiosaurids can be distinguished from other macronarian taxa by their broad, thick and spoon-shaped teeth. Their maxillary teeth were twisted apically, at the top, and the shape of these teeth was optimal for biting off resistant vegetation. While brachiosaurids, like other sauropods, did not perform significant food processing in their mouths, their teeth enabled them to slice through food instead of having to pull it off of tree branches. Evidence for this precision shearing consists of apical wear facets on the teeth and distinctive bone structure that suggests orthal, vertical, jaw action.
In addition, the characteristic long necks of brachiosaurids are distinct from those of other long-necked dinosaur taxa. They possessed a narrow neck composed of twelve to thirteen extremely long cervical vertebrae that was laterally inflexible and dorsoventrally, vertically, flexible. This meant that brachiosaurids could angle their necks up and lift their heads, enabling them to graze from treetops up to a height of about fourteen meters. It has been argued that other sauropods lacked this dorsoventral flexibility and that their necks stretched outwards in front of them instead of upwards. Brachiosaurids have more often been found in the conifer-rich sites, like the Tendaguru, than in the Morrison deposits, suggesting that their fitness was increased by the presence of taller conifer food sources.
However, the giant size and long necks of brachiosaurids meant that they required tremendous pressure to bring oxygenated blood to their brains. 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), but were capable of moving faster when necessary, up to 20–30 km/hour, 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.
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. Since then, the classification of these sauropods has been through many changes. Marsh's multifamily theory of sauropod classification prevailed until 1929, when Werner Janensch proposed a two-family theory based on differences in sauropod teeth. Macronarians with broad, spatulate teeth, were placed in the family Brachiosauridae, while sauropods with more slender and peg-shaped teeth were considered titanosaurids. This put diplodocids and titanosaurids together in one group based on their similar teeth, despite the many other differences between the taxa. Today, about four to five groups within the Macronaria are considered families (with names ending in ~idae).
In 1997, Salgado, Coria and Calvo studied the traits that had been used to set the Brachiosauridae apart and determined that they were in fact plesiomorphic, original, for all basal Titanosauriformes. They proposed that some characteristics that had been used to differentiate Brachiosaurus were synapomorphies for the Titanosauriformes as a whole. They concluded that the family Brachiosauridae was actually a "grade" of not specially related primitive titanosauriforms, and not a stable separate clade. They partly based this conclusion on similar humerus:femur length ratios known for titanosauriforms, basal titanosaurs, and more basal sauropods. However, in 1998 Sereno & Wilson published data contrary to the conclusions in Salgado et al.'s article, indicating that the Brachiosauridae were a separate clade in the Titanosauriformes. After 1998, new brachiosaurid species have been named, generally confirming that the Brachiosauridae were a natural group.
In 1943, de Lapparent described the "French Bothriospondylus" from the Oxfordian of France which dates to the Late Jurassic, which was identified in 2013 by Philip Mannion as a brachiosaurid and named Vouivria damparisensis in 2017. 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.
Definitive brachiosaurid remains have been found from the Late Jurassic Period to the Early Cretaceous, from about 157 to 93 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 Mid-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.
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.
Titanosauriformes was a globally distributed, long-lived clade of dinosaurs that contained both the largest and smallest known sauropods. This clade was composed of three distinct groups: Brachiosauridae, a mix of Late Jurassic and Early Cretaceous sauropods, Euhelopodidae, a group of mid-Cretaceous East Asian sauropods, and Titanosauria, a large Cretaceous clade located mostly in Gondwana.
Traditionally, Brachiosauridae included Brachiosaurus and some other suggestively assigned genera. Following the generic separation of Brachiosaurus species into B. altithorax and Giraffatitan brancai these have sometimes been the only members supported by cladistic analysis.
Cladogram of Brachiosauridae after D'Emic et al. (2016).
Cladogram of Brachiosauridae after Mannion et al. (2017).
Abydosaurus (meaning "Abydos lizard") is a genus of brachiosaurid sauropod dinosaur known from skull and postcranial material found in upper Lower Cretaceous rocks of northeastern Utah, United States.Asiatosaurus
Asiatosaurus (meaning "Asian lizard") was a genus of herbivorous sauropod dinosaur which lived during the early Cretaceous. Its fossils have been found in China and Mongolia. Its type species is known only from teeth, making it difficult to rely on information until more specimens are found to expand our knowledge. The type species, Asiatosaurus mongoliensis, was described by Osborn, in 1924. It was the first sauropod genus named from East-Asia.
Asiatosaurus kwangshiensis was described by Hou, Yeh and Zhao, in 1975 based on a tooth, three cervical vertebrae and multiple ribs from the Xinlong Formation of Guangxi, China. The genus was classified within Brachiosauridae by Hou et al.. Both are now classified as nomina dubia.Bothriospondylus
Bothriospondylus ("excavated vertebra") is a dubious genus of sauropod dinosaur. It lived during the Late Jurassic.Brachiosaurus
Brachiosaurus () is a genus of sauropod dinosaur that lived in North America during the Late Jurassic, about 154–153 million years ago. It was first described by American paleontologist Elmer S. Riggs in 1903 from fossils found in the Colorado River valley in western Colorado, United States. Riggs named the dinosaur Brachiosaurus altithorax; the generic name is Greek for "arm lizard", in reference to its proportionately long arms, and the specific name means "deep chest". Brachiosaurus is estimated to have been between 18 and 21 meters (59 and 69 ft) long; weight estimates range from 28.3 to 58 metric tons (31.2 and 64 short tons). It had a disproportionately long neck, small skull, and large overall size, all of which are typical for sauropods. Atypically, Brachiosaurus had longer forelimbs than hindlimbs, which resulted in a steeply inclined trunk, and a proportionally shorter tail.
Brachiosaurus is the namesake genus of the family Brachiosauridae, which includes a handful of other similar sauropods. Most popular depictions of Brachiosaurus are in fact based on Giraffatitan, a genus of brachiosaurid dinosaur from the Tendaguru Formation of Tanzania. Giraffatitan was originally described by German paleontologist Werner Janensch in 1914 as a species of Brachiosaurus, B. brancai, but moved to its own genus in 2009. Three other species of Brachiosaurus have been named based on fossils found in Africa and Europe; two are no longer considered valid, and a third has become a separate genus, Lusotitan.
The type specimen of B. altithorax is still the most complete specimen, and only a few other specimens are thought to belong to the genus, making it one of the rarer sauropods of the Morrison Formation. It is regarded as a high browser, possibly cropping or nipping vegetation as high as 9 meters (30 ft) off the ground. Unlike other sauropods, 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 suggests it was warm-blooded. Among the most iconic and initially thought to be one of the largest dinosaurs, Brachiosaurus has appeared in popular culture, notably in the 1993 film Jurassic Park.Cedarosaurus
Cedarosaurus (meaning "Cedar lizard" - named after the Cedar Mountain Formation, in which it was discovered) was a nasal-crested macronarian dinosaur genus from the Early Cretaceous Period (Barremian). It was a sauropod which lived in what is now Utah. It was first described by Tidwell, Carpenter and Brooks in 1999.It shows similarities to the brachiosaurid Eucamerotus from the Wessex Formation of southern England, as well as to Brachiosaurus from the Morrison Formation.Daanosaurus
Daanosaurus was a genus of dinosaur. It was a brachiosaurid sauropod which lived during the Late Jurassic (Oxfordian - Tithonian stage, about 163 - 145 mya). It lived in what is now China (Sichuan Province), and was similar to Bellusaurus.
The type species, described in 2005, is Daanosaurus zhangi. Adult size is unknown due to lack of fossil remains.Dystrophaeus
Dystrophaeus is the name given to an extinct genus of eusauropod dinosaur from the early Kimmeridgian stage of the Late Jurassic that existed around 154.8 Ma. Its fossils were found in the Tidwell Member of the Morrison Formation of Utah. Its estimated mass is 12 tonnes (13 short tons).The type species, D. viaemalae, was described by Edward Drinker Cope in 1877. The genus name means "coarse joint" from Greek dys, "bad", and stropheus, "joint", a reference to the pitted joint surfaces serving as an attachment for cartilage. The specific name reads as Latin viae malae, "of the bad road", a reference to the various arduous routes taken to find, reach and salvage the remains. It consists of one partial skeleton, the holotype USNM 2364, which includes a 76 centimetre long ulna, a scapula, a partial radius, and some metacarpals discovered in August 1859 by John Strong Newberry. It was found in what is possibly stratigraphic zone 1 of the Morrison, although an older Oxfordian-Callovian has also been suggested. Dystrophaeus represents one of the oldest discoveries of sauropods in America; earlier, in 1855, some teeth had been found of Astrodon.
The classification of Dystrophaeus has been rather confusing. Cope in 1877 merely concluded it was some Triassic dinosaur. Henri-Émile Sauvage in 1882 understood it was a sauropod, assigning it to the Atlantosauridae. Othniel Charles Marsh however, in 1895 stated it belonged to the Stegosauridae. Friedrich von Huene, the first to determine it was of Jurassic age, in 1904 created a special family for it, the Dystrophaeidae, which he assumed to be herbivorous theropods. Only in 1908 von Huene realised his mistake and classified it in the sauropod Cetiosauridae, refining this in 1927 to the Cardiodontinae. Alfred Romer in 1966 put it in the Brachiosauridae, in a subfamily Cetiosaurinae.
More recently, an analysis by David Gillette concluded it was a member of the Diplodocidae. Another recent review, by Tschopp and colleagues in 2015, suggest it is a member of the Dicraeosauridae. However, many researchers consider the taxon to be a nomen dubium.Europasaurus
Europasaurus is a basal macronarian sauropod, a form of quadrupedal herbivorous dinosaur. It lived during the Late Jurassic (middle Kimmeridgian, about 154 million years ago) of northern Germany, and has been identified as an example of insular dwarfism resulting from the isolation of a sauropod population on an island within the Lower Saxony basin.Jobaria
Jobaria is a genus of sauropod dinosaur that lived in what is now Niger during the middle Jurassic Period, between 164–161 million years ago.Lusotitan
Lusotitan is a genus of herbivorous brachiosaurid sauropod dinosaur from the Late Jurassic Period of Portugal.
In 1947 Manuel de Matos, a member of the Geological Survey of Portugal, discovered large sauropod fossils in the Portuguese Lourinhã Formation that date back to the Tithonian stage of the Late Jurassic period. In 1957 Albert-Félix de Lapparent and Georges Zbyszewski named the remains as a new species of Brachiosaurus: Brachiosaurus atalaiensis. The specific name referred to the site Atalaia. In 2003 Octávio Mateus and Miguel Telles Antunes named it as a separate genus: Lusotitan. The type species is Lusotitan atalaiensis. The generic name is derived from Luso, the Latin name for an inhabitant of Lusitania, and from the Greek word "Titan", a mythological giant.
The finds consisted of a partial skeleton lacking the skull and individual vertebrae uncovered in several locations. De Lapparent did not assign a holotype. In 2003 Mateus chose the skeleton as the lectotype. Its bones have the inventory numbers MIGM 4798, 4801–10, 4938, 4944, 4950, 4952, 4958, 4964–6, 4981–2, 4985, 8807, and 8793-5. These remains include 28 vertebrae and elements of the appendicular skeleton.
It has been estimated that Lusotitan was 25 meters (82 feet) long. It had long forearms, one of the reasons Mateus assigned it to the Brachiosauridae.
The lectotype was re-described by Mannion and colleagues in 2013.Macronaria
Macronaria is a clade of the "suborder" (more likely an unranked clade than a suborder) Sauropodomorpha. Macronarians are named after the large diameter of the nasal opening of their skull, known as the external naris, which exceeded the size of the orbit, the skull opening where the eye is located (hence macro- meaning large, and –naria meaning nose). Fossil evidence suggests that macronarian dinosaurs lived from the Late Jurassic (Kimmeridgian) through the Late Cretaceous (Maastrichtian). Macronarians have been found globally, including discoveries in Argentina, the United States, Portugal, China, and Tanzania. Like other sauropods, they are known to have inhabited primarily terrestrial areas, and little evidence exists to suggest that they spent much time in coastal environments. Macronarians are diagnosed through their distinct characters on their skulls, as well as appendicular and vertebral characters. Macronaria is composed of several subclades and families notably including Camarasauridae and Titanosauriformes, among several others. Titanosauriforms are particularly well known for being some of the largest terrestrial animals to ever exist.
Macronaria was described by Wilson and Sereno who proposed the new subdivisions among the clade Neosauropoda. Previously, this clade was thought to have Brachiosaurus and Camarasauridae forming one sister group, and Titanosauroidea and Diplodocoidea forming another. This proposed shift with Macronaria placed Diplodocoidea as an outgroup to the new clade Macronaria, under which all other neosauropods would fall.Neosauropoda
Neosauropoda is a clade within Dinosauria, coined in 1986 by Argentine paleontologist José Bonaparte and currently described as Saltasaurus loricatus, Diplodocus longus, and all animals directly descended from their most recent common ancestor. The group is composed of two subgroups: Diplodocoidea and Macronaria. Arising in the early Jurassic and persisting until the Cretaceous-Paleogene extinction event, Neosauropoda contains the majority of sauropod genera, including genera such as Apatosaurus, Brachiosaurus, and Diplodocus. It also includes giants such as Argentinosaurus, Patagotitan and Sauroposeidon, and its members remain the largest land animals ever to have lived.When Bonaparte first coined the term Neosauropoda in 1986, he described the clade as comprising “end-Jurassic” sauropods. While Neosauropoda does appear to have originated at the end of the Jurassic period, it also includes members through the end of the Cretaceous. Neosauropoda is currently delineated by specific shared, derived characteristics rather than the time period in which its members lived. The group was further refined by Upchurch, Sereno, and Wilson, who have identified thirteen synapomorphies shared among neosauropods. As Neosauropoda is a subgroup of Sauropoda, all members also display basic sauropod traits such as large size, long necks, and columnar legs.Oplosaurus
Oplosaurus (meaning "armed or weapon lizard" or "armoured lizard"; see below for discussion) was a genus of sauropod dinosaur from the Barremian-age Lower Cretaceous Wessex Formation of the Isle of Wight, England. It is known from a single tooth usually referred to the contemporaneous "wastebasket taxon" Pelorosaurus, although there is no solid evidence for this.Padillasaurus
Padillasaurus is an extinct genus of titanosauriform sauropod known from the Early Cretaceous (Barremian stage) Paja Formation in Colombia. It contains a single species, Padillasaurus leivaensis, known only from a single partial axial skeleton. Initially described as a brachiosaurid, it was considered to be the first South American brachiosaurid ever discovered and named. Before its discovery, the only known brachiosaurid material on the continent was very fragmentary and from the Jurassic period. However, a more recent study finds it to be a basal somphospondylan.Ruyangosaurus
Ruyangosaurus (Ruyang County lizard) is a genus of titanosauriform sauropod dinosaur recovered from the Early Cretaceous Haoling Formation of China. The type species is R. giganteus, described in 2009 by Lü Junchang et al. Along with Huanghetitan and Daxiatitan, Ruyangosaurus is among the largest dinosaurs discovered in Cretaceous Asia.Sonorasaurus
Sonorasaurus is a genus of brachiosaurid dinosaur from the Early to Late Cretaceous (Albian to Cenomanian stages, around 112 to 93 million years ago). It was a herbivorous sauropod whose fossils have been found in southern Arizona in the United States. Its name, which means "Sonora lizard", comes from the Sonoran Desert where its fossils were first found. The type species is S. thompsoni, described by Ratkevich in 1998.Soriatitan
Soriatitan ("Soria titan") is a genus of brachiosaurid sauropod from the Early Cretaceous of Spain. It is known from one species, S. golmayensis, found in the Golmayo Formation. It lived between 138 to 130 million years ago was identified by a team of paleontologists in Spain.Tienshanosaurus
Tienshanosaurus (meaning "Tienshan lizard") is a genus of dinosaur from the Late Jurassic. It was a sauropod which lived in what is now China.Vouivria
Vouivria is a genus of herbivorous sauropod dinosaurs, belonging to the Brachiosauridae, that lived in the area of present France during the Late Jurassic. The type species is Vouivria damparisensis.