The Brachiosauridae ("arm lizards", from Greek ''brachion'' (βραχίων) = "arm" and ''sauros'' = "lizard") are a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

herbivorous A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat n ...

, quadrupedal

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their b ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

s. Brachiosaurids had long necks that enabled them to access the leaves of tall trees that other

sauropods Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their b ...

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 In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to ...

; dorsal vertebrae with 'rod-like' transverse processes and an

ischium The ischium (; : is ...

with an abbreviated pubic peduncle. ''

Brachiosaurus ''Brachiosaurus'' () is a genus of sauropod dinosaur that lived in North America during the Late Jurassic, about . It was first Species description, described by American paleontologist Elmer S. Riggs in 1903 in paleontology, 1903 from fossi ...

'' 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 North is one of the four compass points or cardinal directions. It is the opposite of south and is perpendicular to east and west. ''North'' is a noun, adjective, or adverb indicating Direction (geometry), direction or geography. Etymology T ...

and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

, and

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

. They first appear in the fossil record in the Late

Jurassic Period The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. The Jurassic constitutes the second and m ...

(possibly even earlier in the Middle Jurassic) 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 Pangaea or Pangea ( ) was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous period approximately 335 mi ...

. 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 ''Saltasaurus'' (which means "lizard from Salta") is a genus of saltasaurid dinosaur of the Late Cretaceous Period (geology), period of Argentina. Small among sauropods, though still heavy by the standards of modern creatures, ''Saltasaurus'' was ...

''. It is one of the three main groups of the clade Titanosauriformes, which also includes the

Euhelopodidae Euhelopodidae is a family of sauropod dinosaurs of disputed membership and affinities, which contains '' Euhelopus'' and its close relatives. Most proposed euhelopodids are from East Asia. Euhelopodidae was first recognized by Carl Wiman in 1929 ...

and the

Titanosaur Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still thr ...

ia.

Description

The Brachiosauridae are composed of quadrupedal

s that are generally very large, with the exception of the possible insular dwarf '' Europasaurus''. The brachiosaurids can be distinguished from other

macronaria Macronaria is a clade of sauropod dinosaurs. 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 ...

taxa In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

by their broad, thick and spoon-shaped teeth. Their

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

ry 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 from 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. Vouivria teeth

In addition, the characteristic long necks of brachiosaurids are distinct from those of other long-necked dinosaur

. They possessed a narrow neck composed of twelve to thirteen extremely long

cervical vertebrae In tetrapods, cervical vertebrae (: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In saurop ...

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

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 The Tendaguru Formation, or Tendaguru Beds are a highly fossiliferous formation and Lagerstätte located in the Lindi Region of southeastern Tanzania. The formation represents the oldest sedimentary unit of the Mandawa Basin, overlying Neoprote ...

, than in the

Morrison Morrison may refer to: People * Morrison (surname), people with the Scottish surname Morrison * Morrison Heady (1829–1915), American poet * Morrison Mann MacBride (1877–1938), Canadian merchant Places in the United States * Morrison, Colorad ...

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 Macronaria is a clade of sauropod dinosaurs. 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 ...

, 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 In human anatomy, the metacarpal bones or metacarpus, also known as the "palm bones", are the appendicular bones that form the intermediate part of the hand between the phalanges (fingers) and the carpal bones ( wrist bones), which articulate ...

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

, new traits typical for the group. They possessed middle and rear back

vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

e with long, 'rod-like' transverse processes. In the pelvis, the

ischium The ischium (; : is ...

had a shortened pubic peduncle, the contact surface with the

pubic bone In vertebrates, the pubis or pubic bone () forms the lower and anterior part of each side of the hip bone. The pubis is the most forward-facing (ventral and anterior) of the three bones that make up the hip bone. The left and right pubic bones ar ...

. Their

humeri The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of ...

, upper arm bones, had a large deltopectoral crest. Their skull roofs showed wide supratemporal fenestrae, openings for the muscles. They had

neural arch Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

es placed more on front of the vertebrae, shoulder blades that were expanded at the top end, irregularly shaped

coracoid A coracoid is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is present as part of the scapula, but this is n ...

s in the shoulder girdle, and triangular projections on the underside of the front branch of their

quadratojugal bone The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians. Anatomy and function In animals with a quadratojugal bone, it is typically found connected to the jugal (cheek) bone from the front and ...

s at the lower rear corner of the skull.

History of findings

Changing classifications

In 1903, Elmer Samuel Riggs described and named ''

''. In 1904, he created a new sauropod family, the Brachiosauridae.Riggs, E.S. 1904. "Structure and relationships of opisthocoelian dinosaurs. Part II, the Brachiosauridae". ''Field Columbian Museum, Geological Series 2'' 6: 229-247 He published a complete description of the

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...

after examining the

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

, and

sacrum The sacrum (: sacra or sacrums), in human anatomy, is a triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part of the pelvic cavity, ...

of the ''Brachiosaurus''

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

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 Werner Ernst Martin Janensch (11 November 1878 – 20 October 1969) was a German paleontologist and geologist. Biography Janensch was born at Herzberg (Elster). In addition to Friedrich von Huene, Janensch was probably Germany's most ...

proposed a two-family theory based on differences in sauropod teeth.

ns with broad, spatulate teeth, were placed in the family Brachiosauridae, while sauropods with more slender and peg-shaped teeth were considered

titanosaurs Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of Sauropoda, sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with tax ...

. This put

diplodocid Diplodocids, or members of the family Diplodocidae ("double beams"), are a group of sauropod dinosaurs. The family includes some of the longest creatures ever to walk the Earth, including '' Diplodocus'' and '' Supersaurus'', some of which may ha ...

s and titanosaurids together in one group based on their similar teeth, despite the many other differences between the

. Today, about four to five groups within the Macronaria are considered families (with names ending in ~). 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 In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, an ...

, original, for all basal Titanosauriformes. They proposed that some characteristics that had been used to differentiate ''Brachiosaurus'' were

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

. 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.

Important findings

In 1943, de Lapparent described the "French Bothriospondylus" from the Oxfordian of France which dates to the

Late Jurassic The Late Jurassic is the third Epoch (geology), epoch of the Jurassic Period, and it spans the geologic time scale, geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic stratum, strata.Owen ...

, 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 ''Duriatitan'' is a genus of titanosauriform sauropod dinosaur that lived in the Late Jurassic in what is now England. The holotype specimen of ''Duriatitan'', BMNH 44635, is a partial left upper arm bone which was found by R.I. Smith nea ...

'' at least 136 years. ImageSize = width:1500px height:auto barincrement:15px PlotArea = left:10px bottom:50px top:10px right:10px Period = from:1824 till:2100 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:50 start:1824 ScaleMinor = unit:year increment:10 start:1824 TimeAxis = orientation:hor AlignBars = justify Colors = #legends id:CAR value:claret id:ANK value:rgb(0.4,0.3,0.196) id:HER value:teal id:HAD value:green id:OMN value:blue id:black value:black id:white value:white id:1900s value:rgb(0.94,0.25,0.24) id:2000s value:rgb(0.2,0.7,0.79) id:2000syears value:rgb(0.52,0.81,0.91) id:1900syears value:rgb(0.95,0.56,0.45) id:1700s value:rgb(0.5,0.78,0.31) id:1700syears value:rgb(0.63,0.78,0.65) id:latecretaceous value:rgb(0.74,0.82,0.37) id:1800syears value:rgb(0.95,0.98,0.11) id:paleogene value:rgb(0.99,0.6,0.32) id:paleocene value:rgb(0.99,0.65,0.37) id:eocene value:rgb(0.99,0.71,0.42) id:oligocene value:rgb(0.99,0.75,0.48) id:1800s value:rgb(0.999999,0.9,0.1) id:miocene 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 The prokaryotic small ribosomal subunit, or 30Svedberg, S subunit, is the smaller subunit of the 70S ribosome found in prokaryotes. It is a complex of the 16S ribosomal RNA (rRNA) and 19 proteins. This complex is implicated in the binding of tr ...

from: 1840 till: 1850 color:1800syears text: 40s from: 1850 till: 1860 color:1800syears text:

50s 50 S is the larger subunit of the 70S ribosome of prokaryotes, i.e. bacteria and archaea. It is the site of inhibition for antibiotics such as macrolides, chloramphenicol, clindamycin, and the pleuromutilins. It includes the 5S ribosom ...

from: 1860 till: 1870 color:1800syears text: 60s from: 1870 till: 1880 color:1800syears text:

70s Ribosomes () are macromolecular machines, found within all cells, that perform biological protein synthesis (messenger RNA translation). Ribosomes link amino acids together in the order specified by the codons of messenger RNA molecules to fo ...

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:

from: 1940 till: 1950 color:1900syears text: 40s from: 1950 till: 1960 color:1900syears text:

from: 1960 till: 1970 color:1900syears text: 60s from: 1970 till: 1980 color:1900syears text:

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:

from: 2040 till: 2050 color:2000syears text: 40s from: 2050 till: 2060 color:2000syears text:

from: 2060 till: 2070 color:2000syears text: 60s from: 2070 till: 2080 color:2000syears text:

from: 2080 till: 2090 color:2000syears text: 80s from: 2090 till: 2100 color:2000syears text: 90s bar:eratop from: 1824 till: 1900 color:1800s text: 19th from: 1900 till: 2000 color:1900s text: 20th from: 2000 till: 2100 color:2000s text: 21st PlotData= align:left fontsize:M 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 ''Giraffatitan'' (name meaning "titanic giraffe") is a genus of sauropod dinosaur that lived during the late Jurassic Period (geology), Period (Kimmeridgian–Tithonian stages) in what is now Lindi Region, Tanzania. Only one species is known, ...

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:

from: 1840 till: 1850 color:1800syears text: 40s from: 1850 till: 1860 color:1800syears text:

from: 1860 till: 1870 color:1800syears text: 60s from: 1870 till: 1880 color:1800syears text:

from: 1940 till: 1950 color:1900syears text: 40s from: 1950 till: 1960 color:1900syears text:

from: 1960 till: 1970 color:1900syears text: 60s from: 1970 till: 1980 color:1900syears text:

from: 2040 till: 2050 color:2000syears text: 40s from: 2050 till: 2060 color:2000syears text:

from: 2060 till: 2070 color:2000syears text: 60s from: 2070 till: 2080 color:2000syears text:

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

Giraffatitan brancai Naturkundemuseum Berlin

Definitive brachiosaurid remains have been found from the Late Jurassic Period to the

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

, from about 157 to 100 million years ago. In addition,

in general first appear in the

. However, the almost simultaneous appearance of ''

Camarasaurus ''Camarasaurus'' ( ) is a genus of sauropod dinosaur that lived in North America during the Late Jurassic period. Its fossil remains have been found in the Morrison Formation, dating to the Kimmeridgian and Tithonian ages of the Jurassic, betwe ...

'', ''

'', and a possible

titanosaur Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still thr ...

suggest that they originated earlier, closer to the Mid-Jurassic. Trackway evidence also supports a

Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 161.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relativel ...

origin for titanosaurs, which implies the same for all neosauropods. Brachiosaurids in particular have a broad distribution dating to the

specimens have been discovered in the northern and southern Hemispheres, including

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, and

. This suggests that brachiosaurids originated in the

, prior to the breakup of

, followed by diversification and dispersal that resulted in the global spread present in the Late Jurassic. This conclusion is further supported by

paleogeographic Palaeogeography (or paleogeography) is the study of historical geography, generally physical landscapes. Palaeogeography can also include the study of human or cultural environments. When the focus is specifically on landforms, the term paleo ...

data. While many Late Jurassic dinosaur remains have been found in

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

, 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 A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

record. Recently discovered evidence supports the conclusion that brachiosaurids existed outside of North America in lower latitudes of

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

in the Early Cretaceous. In 2013, Mannion et al. reported on the discovery of two isolated teeth found in

Lebanon Lebanon, officially the Republic of Lebanon, is a country in the Levant region of West Asia. Situated at the crossroads of the Mediterranean Basin and the Arabian Peninsula, it is bordered by Syria to the north and east, Israel to the south ...

from the Early Cretaceous that possess posteriorly twisted crowns, which are characteristic of the brachiosaurids ''

'' and '' Abydosaurus''. In addition, a brachiosaurid named '' Padillasaurus leivaensis'' was discovered in

Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

from the Early Cretaceous and placed in the Brachiosauridae

taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

, 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

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 A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

. 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

s of Titanosauriformes, a diverse group of

that existed in the

and

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pa ...

and

. '' Europasaurus'' is considered the most basal brachiosaurid. Titanosauriformes was a globally distributed, long-lived

s that contained both the largest and smallest known

. This

was composed of three distinct groups: Brachiosauridae, a mix of

and

, a group of mid-

East Asian

, and

ia, a large

located mostly in

. Traditionally, Brachiosauridae included ''

'' 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 Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...

analysis. Cladogram of Brachiosauridae after D'Emic ''et al.'' (2016). Cladogram of Brachiosauridae after Mannion ''et al.'' (2017).

References

External links

Artist's rendering of fourteen brachiosaursBrachiosauridae
{{Taxonbar, from=Q131146 Dinosaur families