Sauropoda (), whose members are known as sauropods (; from ''
sauro-'' + ''
-pod'', '
lizard
Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...
-footed'), is a
clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
of
saurischia
Saurischia ( , meaning "reptile-hipped" from the Greek ' () meaning 'lizard' and ' () meaning 'hip joint') is one of the two basic divisions of dinosaurs (the other being Ornithischia), classified by their hip structure. Saurischia and Ornithis ...
n ('lizard-hipped')
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s. Sauropods had very long necks, long tails, small heads (relative to the rest of their body), and four thick, pillar-like legs. They are notable for the enormous sizes attained by some species, and the group includes the largest animals to have ever lived on land. Well-known
genera
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...
include ''
Brachiosaurus
''Brachiosaurus'' () is a genus of sauropod dinosaur that lived in North America during the Late Jurassic, about 154to 150million years ago. It was first described by American paleontologist Elmer S. Riggs in 1903 from fossils found in th ...
'', ''
Diplodocus
''Diplodocus'' (, , or ) was a genus of diplodocid sauropod dinosaurs, whose fossils were first discovered in 1877 by S. W. Williston. The generic name, coined by Othniel Charles Marsh in 1878, is a neo-Latin term derived from Greek διπ ...
'', ''
Apatosaurus
''Apatosaurus'' (; meaning "deceptive lizard") is a genus of herbivorous sauropod dinosaur that lived in North America during the Late Jurassic period. Othniel Charles Marsh described and named the first-known species, ''A. ajax'', in 1877, an ...
'' and ''
Brontosaurus
''Brontosaurus'' (; meaning "thunder lizard" from Greek , "thunder" and , "lizard") is a genus of gigantic quadruped sauropod dinosaurs. Although the type species, ''B. excelsus'', had long been considered a species of the closely related ''A ...
''.
The oldest known unequivocal sauropod dinosaurs are known from the
Early Jurassic
The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...
.
''
Isanosaurus
''Isanosaurus'' means "North-eastern thailand lizard" was a sauropod dinosaur from Thailand. It was originally dated to approximately 210 million years ago during the Late Triassic (late Norian to Rhaetian stages), which would make it on ...
'' and ''
Antetonitrus
''Antetonitrus'' is a genus of sauropod dinosaur found in the Early Jurassic Elliot Formation of South Africa. The only species is ''Antetonitrus ingenipes''. As one of the oldest known sauropods, it is crucial for the understanding of the origi ...
'' were originally described as
Triassic
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...
sauropods, but their age, and in the case of ''Antetonitrus'' also its sauropod status, were subsequently questioned.
Sauropod-like sauropodomorph tracks from the
Fleming Fjord Formation
The Fleming Fjord Formation, alternatively called the Fleming Fjord Group is an Upper Triassic geological formation in the northeastern coast of Jameson Land, Greenland. It consists of terrestrial sediments and is known for its fossil content.
...
(
Greenland
Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...
) might, however, indicate the occurrence of the group in the
Late Triassic
The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch ...
.
By the
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987.
In European lithostratigraphy, the name ...
(150 million years ago), sauropods had become widespread (especially the
diplodocids and
brachiosaurid
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 le ...
s). By the
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...
, one group of sauropods, 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 th ...
s, had replaced all others and had a near-global distribution. However, as with all other non-avian dinosaurs alive at the time, 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 th ...
s died out in the
Cretaceous–Paleogene extinction event
The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary extinction) was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the ...
.
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 preserved ...
ised remains of sauropods have been found on every continent, including
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...
.
The name Sauropoda was coined by
Othinel Charles Marsh in 1878, and is derived from
Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...
, meaning "lizard foot".
Sauropods are one of the most recognizable groups of dinosaurs, and have become a fixture in popular culture due to their impressive size.
Complete sauropod fossil finds are rare. Many species, especially the largest, are known only from isolated and disarticulated bones. Many near-complete specimens lack heads, tail tips and limbs.
Description
Sauropods were
herbivorous
A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...
(plant-eating), usually quite long-necked
quadruped
Quadrupedalism is a form of locomotion where four limbs are used to bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four limbs is said to be a quadruped (from Latin ''quattuor' ...
s (four-legged), often with spatulate (spatula-shaped: broad at the tip, narrow at the neck) teeth. They had tiny heads, massive bodies, and most had long tails. Their hind legs were thick, straight, and powerful, ending in club-like feet with five toes, though only the inner three (or in some cases four) bore claws. Their forelimbs were rather more slender and typically ended in pillar-like hands built for supporting weight; often only the thumb bore a claw. Many illustrations of sauropods in the flesh miss these facts, inaccurately depicting sauropods with hooves capping the claw-less digits of the feet, or more than three claws or hooves on the hands. The
proximal
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...
caudal vertebrae
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
are extremely
diagnostic
Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine " cause and effect". In systems engine ...
for sauropods.
[Tidwell, V., Carpenter, K. & Meyer, S. 2001. New Titanosauriform (Sauropoda) from the Poison Strip Member of the Cedar Mountain Formation (Lower Cretaceous), Utah. In: Mesozoic Vertebrate Life. D. H. Tanke & K. Carpenter (eds.). Indiana University Press, Eds. D.H. Tanke & K. Carpenter. Indiana University Press. 139-165.]
Size
![Longest dinosaurs2](https://upload.wikimedia.org/wikipedia/commons/3/34/Longest_dinosaurs2.svg)
The sauropods' most defining characteristic was their size. Even the dwarf sauropods (perhaps 5 to 6 metres, or 20 feet long) were counted among the largest animals in their
ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
. Their only real competitors in terms of size are the
rorqual
Rorquals () are the largest group of baleen whales, which comprise the family Balaenopteridae, containing ten extant species in three genera. They include the largest animal that has ever lived, the blue whale, which can reach , and the fin wha ...
s, such as the
blue whale
The blue whale (''Balaenoptera musculus'') is a marine mammal and a baleen whale. Reaching a maximum confirmed length of and weighing up to , it is the largest animal known to have ever existed. The blue whale's long and slender body can ...
. But, unlike whales, sauropods were primarily
terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land (e.g. cats, dogs, ants, spiders), as compared with aquatic animals, which live predominantly or entirely in the water (e.g. fish, lobsters, octopuses), and amphibians, ...
s.
Their body structure did not vary as much as other dinosaurs, perhaps due to size constraints, but they displayed ample variety. Some, like the
diplodocids, possessed tremendously long tails, which they may have been able to
crack like a
whip
A whip is a tool or weapon designed to strike humans or other animals to exert control through pain compliance or fear of pain. They can also be used without inflicting pain, for audiovisual cues, such as in equestrianism. They are generally e ...
as a signal or to deter or injure predators, or to make
sonic boom
A sonic boom is a sound associated with shock waves created when an object travels through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding similar to an explosion or a thunderclap to t ...
s.
''
Supersaurus
''Supersaurus'' (meaning "super lizard") is a genus of diplodocid Sauropoda, sauropod dinosaur that lived in North America during the Late Jurassic period. The type species, ''S. vivianae'', was first discovered by Vivian Jones of Delta, Colorad ...
'', at long,
was the longest sauropod known from reasonably complete remains, but others, like the old record holder, ''
Diplodocus
''Diplodocus'' (, , or ) was a genus of diplodocid sauropod dinosaurs, whose fossils were first discovered in 1877 by S. W. Williston. The generic name, coined by Othniel Charles Marsh in 1878, is a neo-Latin term derived from Greek διπ ...
'', were also extremely long. The
holotype
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...
(and now lost)
vertebra
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
of ''
Amphicoelias fragillimus
''Maraapunisaurus'' is a genus of sauropod dinosaur from the Late Jurassic Morrison Formation of western North America. It is known only from what has sometimes been estimated to be the Dinosaur size, largest dinosaur specimen ever discovered, o ...
'' (now ''Maraapunisaurus'') may have come from an animal long;
its vertebral column would have been substantially longer than that of the blue whale. However, research published in 2015 speculated that the size estimates of ''A. fragillimus'' may have been highly exaggerated.
The longest dinosaur known from reasonable fossils material is probably ''
Argentinosaurus
''Argentinosaurus'' is a genus of giant sauropod dinosaur that lived during the Late Cretaceous period in what is now Argentina. Although it is only known from fragmentary remains, ''Argentinosaurus'' is one of the largest known land animals o ...
huinculensis'' with length estimates of to according to the most recent researches.
However the giant ''
Barosaurus
''Barosaurus'' ( ) was a giant, long-tailed, long-necked, plant-eating sauropod dinosaur closely related to the more familiar ''Diplodocus''. Remains have been found in the Morrison Formation from the Upper Jurassic Period of Utah and South Da ...
'' specimen BYU 9024 might have been even larger reaching lengths of 45–48 meters (148–157 ft).
The longest terrestrial animal alive today, the
African elephant, can only reach lengths of .
Others, like the
brachiosaurids, were extremely tall, with high shoulders and extremely long necks. The tallest sauropod was the giant ''Barosaurus'' specimen at tall.
By comparison, the
giraffe
The giraffe is a large African hoofed mammal belonging to the genus ''Giraffa''. It is the tallest living terrestrial animal and the largest ruminant on Earth. Traditionally, giraffes were thought to be one species, ''Giraffa camelopardalis ...
, the tallest of all living land animals, is only 4.8 to 5.6 metres (15.74 to 18.3 ft) tall.
The best evidence indicates that the most massive were ''
Argentinosaurus
''Argentinosaurus'' is a genus of giant sauropod dinosaur that lived during the Late Cretaceous period in what is now Argentina. Although it is only known from fragmentary remains, ''Argentinosaurus'' is one of the largest known land animals o ...
'' (65-80 metric tons
),
''Mamenchisaurus sinocanadorum'' (60-80 metric tons
), the giant ''
Barosaurus
''Barosaurus'' ( ) was a giant, long-tailed, long-necked, plant-eating sauropod dinosaur closely related to the more familiar ''Diplodocus''. Remains have been found in the Morrison Formation from the Upper Jurassic Period of Utah and South Da ...
'' specimen (60-80+ metric tons
) and ''
Patagotitan
''Patagotitan'' is a genus of titanosaurian sauropod dinosaur from the Cerro Barcino Formation in Chubut Province, Patagonia, Argentina. The genus contains a single species known from multiple individuals: ''Patagotitan mayorum'', first announc ...
'' with ''
Puertasaurus
''Puertasaurus'' is a genus of sauropod dinosaur that lived in South America during the Late Cretaceous Period. It is known from a single specimen recovered from sedimentary rocks of the Cerro Fortaleza Formation in southwestern Patagonia, Ar ...
'' (50-55
metric ton
The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton (United States c ...
s
). There was poor (and now missing) evidence that so-called ''
Bruhathkayosaurus'', might have weighed over 175 metric tons but this has been questioned. The supposed fibula was probably a femur of an animal slightly larger than ''
Dreadnoughtus
''Dreadnoughtus'' is a genus of titanosaurian sauropod dinosaur containing a single species, ''Dreadnoughtus schrani''. ''D. schrani'' is known from two partial skeletons discovered in Upper Cretaceous (Campanian to Maastrichtian; approximately ...
.''
The weight of ''
Amphicoelias fragillimus
''Maraapunisaurus'' is a genus of sauropod dinosaur from the Late Jurassic Morrison Formation of western North America. It is known only from what has sometimes been estimated to be the Dinosaur size, largest dinosaur specimen ever discovered, o ...
'' was estimated at 122.4 metric tons
but 2015 research argued that these estimates may have been highly exaggerated.
Additional finds indicate a number of species likely reached or exceeded weights of 40 tons.
The largest land animal alive today, the
bush elephant
The African bush elephant (''Loxodonta africana'') is one of two extant African elephant species and one of three extant elephant species. It is the largest living terrestrial animal, with bulls reaching a shoulder height of up to and a body ...
, weighs no more than .
Among the smallest sauropods were the primitive ''
Ohmdenosaurus
''Ohmdenosaurus'' ("Ohmden lizard") is a genus of sauropod dinosaur that lived during the Early Jurassic epoch in what is now Germany. The only specimen – a tibia (shinbone) and ankle – was discovered in rocks of the Posidonia Shale near Ho ...
'' (4 m, or 13 ft long), the dwarf
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 th ...
''
Magyarosaurus
''Magyarosaurus'' (" Magyar lizard") is a genus of dwarf sauropod dinosaur from late Cretaceous Period (early to late Maastrichtian) in Romania. It is one of the smallest-known adult sauropods, measuring only in length and in body mass. The t ...
'' (6 m or 20 ft long), and the dwarf
brachiosaurid
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 le ...
''
Europasaurus'', which was 6.2 meters long as a fully-grown adult.
Its small stature was probably the result of
insular dwarfism
Insular dwarfism, a form of phyletic dwarfism, is the process and condition of large animals evolving or having a reduced body size when their population's range is limited to a small environment, primarily islands. This natural process is disti ...
occurring in a population of sauropods isolated on an island of the late Jurassic in what is now the Langenberg area of northern
Germany
Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...
.
The
diplodocoid
Diplodocoidea is a superfamily of sauropod dinosaurs, which included some of the longest animals of all time, including slender giants like ''Supersaurus'', ''Diplodocus'', ''Apatosaurus'', and ''Amphicoelias''. Most had very long necks and long, ...
sauropod ''
Brachytrachelopan
''Brachytrachelopan'' is a short-necked sauropod dinosaur from the Late Jurassic ( Oxfordian to Tithonian) of Argentina. The holotype and only known specimen (Museo Paleontológico Egidio Feruglio MPEF-PV 1716) was collected from an erosion ...
'' was the shortest member of its group because of its unusually short neck. Unlike other sauropods, whose necks could grow to up to four times the length of their backs, the neck of ''Brachytrachelopan'' was shorter than its backbone.
Fossils from perhaps the largest dinosaur ever found were discovered in 2012 in the Neuquén Province of northwest Patagonia, Argentina. It is believed that they are from a titanosaur, which were amongst the largest sauropods.
[
On or shortly before 29 March 2017 a sauropod footprint about 5.6 feet (1.7 meters) long was found at Walmadany in the Kimberley Region of Western Australia. The report said that it was the biggest known yet. In 2020 Molina-Perez and Larramendi estimated the size of the animal at 31 meters (102 ft) and 72 tonnes (79.4 short tons) based on the 1.75 meter (5.7 ft) long footprint.]
Limbs and feet
As massive quadruped
Quadrupedalism is a form of locomotion where four limbs are used to bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four limbs is said to be a quadruped (from Latin ''quattuor' ...
s, sauropods developed specialized "graviportal" (weight-bearing) limbs. The hind feet were broad, and retained three claws in most species. Particularly unusual compared with other animals were the highly modified front feet ('' manus''). The front feet of sauropods were very dissimilar from those of modern large quadrupeds, such as elephant
Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantidae an ...
s. Rather than splaying out to the sides to create a wide foot as in elephants, the manus bones of sauropods were arranged in fully vertical columns, with extremely reduced finger bones (though it is not clear if the most primitive sauropods, such as ''Vulcanodon
''Vulcanodon'' (meaning "volcano tooth") is an extinct genus of sauropod dinosaur from the Early Jurassic of southern Africa. The only known species is ''V. karibaensis''. Discovered in 1969 in Zimbabwe, it was regarded as the earliest-known sau ...
'' and ''Barapasaurus
''Barapasaurus'' ( ) is a genus of basal sauropod dinosaur from Early Jurassic rocks of India. The only species is ''B. tagorei''. ''Barapasaurus'' comes from the lower part of the Kota Formation, that dates back to the Sinemurian and Pliensb ...
'', had such forefeet). The front feet were so modified in eusauropods that individual digits would not have been visible in life.
The arrangement of the forefoot bone (''metacarpal
In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist, which forms the connection to the forearm. The metacarpal bones ...
'') columns in eusauropods was semi-circular, so sauropod forefoot prints are horseshoe-shaped. Unlike elephants, print evidence shows that sauropods lacked any fleshy padding to back the front feet, making them concave. The only claw visible in most sauropods was the distinctive thumb claw (associated with digit I). Almost all sauropods had such a claw, though what purpose it served is unknown. The claw was largest (as well as tall and laterally flattened) in diplodocids, and very small in brachiosaurids, some of which seem to have lost the claw entirely based on trackway evidence. Titanosaurs may have lost the thumb claw completely (with the exception of early forms, such as ''Janenschia
''Janenschia'' (named after Werner Janensch) is a large herbivorous sauropod dinosaur from the Late Jurassic Tendaguru Formation of Lindi Region, Tanzania around 155 million years ago.
Discovery and naming
''Janenschia'' has had a convolut ...
'').
Titanosaurs were most unusual among sauropods, as, across their history as a clade, they lost not just the external claw but also completely lost the digits of the front foot. Advanced titanosaurs had no digits or digit bones, and walked only on horseshoe-shaped "stumps" made up of the columnar metacarpal bones.[Apesteguía, S. (2005). "Evolution of the titanosaur metacarpus". Pp. 321-345 in Tidwell, V. and Carpenter, K. (eds.) ''Thunder-Lizards: The Sauropodomorph Dinosaurs''. Indianapolis: Indiana University Press.]
Print evidence from Portugal
Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...
shows that, in at least some sauropods (probably brachiosaurids), the bottom and sides of the forefoot column was likely covered in small, spiny scales, which left score marks in the prints. In titanosaurs, the ends of the metacarpal bones that contacted the ground were unusually broad and squared-off, and some specimens preserve the remains of soft tissue covering this area, suggesting that the front feet were rimmed with some kind of padding in these species.
Matthew Bonnan
Matthew Bonnan is an American paleobiologist, a Professor of Biological Sciences at Stockton University, and as of 2021 a singer/songwriter. His research combines traditional descriptive and anatomical study with computer-aided morphometric ana ...
has shown that sauropod dinosaur long bones grew isometrically: that is, there was little to no change in shape as juvenile sauropods became gigantic adults. Bonnan suggested that this odd scaling pattern (most vertebrates show significant shape changes in long bones associated with increasing weight support) might be related to a stilt-walker principle (suggested by amateur scientist Jim Schmidt) in which the long legs of adult sauropods allowed them to easily cover great distances without changing their overall mechanics.
Air sacs
Along with other saurischia
Saurischia ( , meaning "reptile-hipped" from the Greek ' () meaning 'lizard' and ' () meaning 'hip joint') is one of the two basic divisions of dinosaurs (the other being Ornithischia), classified by their hip structure. Saurischia and Ornithis ...
n dinosaurs (such as theropods
Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ca ...
, including birds), sauropods had a system of air sac
Air sacs are spaces within an organism where there is the constant presence of air. Among modern animals, birds possess the most air sacs (9–11), with their extinct dinosaurian relatives showing a great increase in the pneumatization (presence ...
s, evidenced by indentations and hollow cavities in most of their vertebra
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
e that had been invaded by them. Pneumatic, hollow bones are a characteristic feature of all sauropods.[Wedel, M.J. (2009).]
Evidence for bird-like air sacs in Saurischian dinosaurs
. (pdf) ''Journal of Experimental Zoology'', 311A: 18pp. These air spaces reduced the overall weight of the massive necks that the sauropods had, and the air-sac system in general, allowing for a single-direction airflow through stiff lungs, made it possible for the sauropods to get enough oxygen.
The bird-like hollowing of sauropod bones was recognized early in the study of these animals, and, in fact, at least one sauropod specimen found in the 19th century (''Ornithopsis
''Ornithopsis'' (meaning "bird-likeness") was a medium-sized Early Cretaceous sauropod dinosaur, from England. The type species, which is the only species seen as valid today, is ''O. hulkei''.
History of discovery
Gideon Algernon Mantell descr ...
'') was originally misidentified as a pterosaur
Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 to ...
(a flying reptile) because of this.[Taylor, M.P. (2010). "Sauropod dinosaur research: a historical review". In Richard Moody, Eric Buffetaut, David M. Martill and Darren Naish (eds.), ''Dinosaurs (and other extinct saurians): a historical perspective'']
HTML abstract
Armor
Some sauropods had armor
Armour (British English) or armor (American English; see spelling differences) is a covering used to protect an object, individual, or vehicle from physical injury or damage, especially direct contact weapons or projectiles during combat, or fr ...
. There were genera with small club
Club may refer to:
Arts, entertainment, and media
* ''Club'' (magazine)
* Club, a ''Yie Ar Kung-Fu'' character
* Clubs (suit), a suit of playing cards
* Club music
* "Club", by Kelsea Ballerini from the album ''kelsea''
Brands and enterprises
...
s on their tails, a prominent example being ''Shunosaurus
''Shunosaurus'', meaning "shu lizard", is a genus of sauropod dinosaur from Late Jurassic ( Oxfordian) beds in Sichuan Province in China, approximately 159±2 million years ago. The name derives from "Shu", an ancient name for the Sichuan p ...
'', and several 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 th ...
s, such as ''Saltasaurus
''Saltasaurus'' (which means "lizard from Salta") is a genus of saltasaurid dinosaur of the Late Cretaceous period of Argentina. Small among sauropods, though still heavy by the standards of modern creatures, ''Saltasaurus'' was characterized by ...
'' and ''Ampelosaurus
''Ampelosaurus'' ( ; meaning "vine lizard") is a titanosaurian sauropod dinosaur from the Late Cretaceous Period of what is now France. Its type species is ''A. atacis'', named by Le Loeuff in 1995. A possible unnamed species has given ''Ampel ...
'', had small bony osteoderm
Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amp ...
s covering portions of their bodies.
Teeth
A study by Michael D’Emic and his colleagues from Stony Brook University found that sauropods evolved high tooth replacement rates to keep up with their large appetites. The study suggested that ''Nigersaurus'', for example, replaced each tooth every 14 days, ''Camarasaurus'' replaced each tooth every 62 days, and ''Diplodocus'' replaced each tooth once every 35 days. The scientists found qualities of the tooth affected how long it took for a new tooth to grow. ''Camarasaurus'''s teeth took longer to grow than those for ''Diplodocus'' because they were larger.
It was also noted by D'Emic and his team that the differences between the teeth of the sauropods also indicated a difference in diet. ''Diplodocus'' ate plants low to the ground and ''Camarasaurus'' browsed leaves from top and middle branches. According to the scientists, the specializing of their diets helped the different herbivorous dinosaurs to coexist.
Necks
Sauropod necks have been found at over in length, a full six times longer than the world record giraffe neck. Enabling this were a number of essential physiological features. The dinosaurs’ overall large body size and quadrupedal stance provided a stable base to support the neck, and the head was evolved to be very small and light, losing the ability to orally process food. By reducing their heads to simple harvesting tools that got the plants into the body, the sauropods needed less power to lift their heads, and thus were able to develop necks with less dense muscle and connective tissue. This drastically reduced the overall mass of the neck, enabling further elongation.
Sauropods also had a great number of adaptations in their skeletal structure. Some sauropods had as many as 19 cervical vertebrae
In tetrapods, cervical vertebrae (singular: 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 ...
, whereas almost all mammals are limited to only seven. Additionally, each vertebra was extremely long and had a number of empty spaces in them which would have been filled only with air. An air-sac system connected to the spaces not only lightened the long necks, but effectively increased the airflow through the trachea, helping the creatures to breathe in enough air. By evolving vertebrae consisting of 60% air, the sauropods were able to minimize the amount of dense, heavy bone without sacrificing the ability to take sufficiently large breaths to fuel the entire body with oxygen. According to Kent Stevens, computer-modeled reconstructions of the skeletons made from the vertebrae indicate that sauropod necks were capable of sweeping out large feeding areas without needing to move their bodies, but were unable to be retracted to a position much above the shoulders for exploring the area or reaching higher.
Another proposed function of the sauropods’ long necks was essentially a radiator to deal with the extreme amount of heat produced from their large body mass. Considering that the metabolism would have been doing an immense amount of work, it would certainly have generated a large amount of heat as well, and elimination of this excess heat would have been essential for survival.
It has also been proposed that the long necks would have cooled the veins and arteries going to the brain, avoiding excessively heated blood from reaching the head. It was in fact found that the increase in metabolic rate resulting from the sauropods’ necks was slightly more than compensated for by the extra surface area from which heat could dissipate.
Palaeobiology
Ecology
When sauropods were first discovered, their immense size led many scientists to compare them with modern-day whale
Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...
s. Most studies in the 19th and early 20th centuries concluded that sauropods were too large to have supported their weight on land, and therefore that they must have been mainly aquatic. Most life restorations of sauropods in art through the first three quarters of the 20th century depicted them fully or partially immersed in water. This early notion was cast in doubt beginning in the 1950s, when a study by Kermack (1951) demonstrated that, if the animal were submerged in several metres of water, the pressure would be enough to fatally collapse the lungs and airway. However, this and other early studies of sauropod ecology
Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...
were flawed in that they ignored a substantial body of evidence that the bodies of sauropods were heavily permeated with air sacs
Air sacs are spaces within an organism where there is the constant presence of air. Among modern animals, birds possess the most air sacs (9–11), with their extinct dinosaurian relatives showing a great increase in the pneumatization (presence ...
. In 1878, paleontologist E.D. Cope had even referred to these structures as "floats".
Beginning in the 1970s, the effects of sauropod air sacs on their supposed aquatic lifestyle began to be explored. Paleontologists such as Coombs and Bakker used this, as well as evidence from sedimentology
Sedimentology encompasses the study of modern sediments such as sand, silt, and clay, and the processes that result in their formation (erosion and weathering), transport, deposition and diagenesis. Sedimentologists apply their understanding of mo ...
and biomechanics
Biomechanics is the study of the structure, function and motion of the mechanical aspects of biological systems, at any level from whole organisms to organs, cells and cell organelles, using the methods of mechanics. Biomechanics is a branch of ...
, to show that sauropods were primarily terrestrial animals. In 2004, D.M. Henderson noted that, due to their extensive system of air sacs, sauropods would have been buoyant and would not have been able to submerge their torsos completely below the surface of the water; in other words, they would float, and would not have been in danger of lung collapse due to water pressure when swimming.[
Evidence for swimming in sauropods comes from fossil trackways that have occasionally been found to preserve only the forefeet (manus) impressions. Henderson showed that such trackways can be explained by sauropods with long forelimbs (such as ]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 ...
ns) floating in relatively shallow water deep enough to keep the shorter hind legs free of the bottom, and using the front limbs to punt forward.[ However, due to their body proportions, floating sauropods would also have been very unstable and maladapted for extended periods in the water. This mode of aquatic ]locomotion
Locomotion means the act or ability of something to transport or move itself from place to place.
Locomotion may refer to:
Motion
* Motion (physics)
* Robot locomotion, of man-made devices
By environment
* Aquatic locomotion
* Flight
* Locomo ...
, combined with its instability, led Henderson to refer to sauropods in water as "tipsy punters".[
While sauropods could therefore not have been aquatic as historically depicted, there is evidence that they preferred wet and coastal habitats. Sauropod footprints are commonly found following coastlines or crossing floodplains, and sauropod fossils are often found in wet environments or intermingled with fossils of marine organisms.][ A good example of this would be the massive ]Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
sauropod trackways found in lagoon
A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') a ...
deposits on Scotland
Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...
's Isle of Skye
The Isle of Skye, or simply Skye (; gd, An t-Eilean Sgitheanach or ; sco, Isle o Skye), is the largest and northernmost of the major islands in the Inner Hebrides of Scotland. The island's peninsulas radiate from a mountainous hub dominated ...
. Studies published in 2021 suggest sauropods could not inhabit polar regions. This study suggests they were largely confined to tropical areas and had metabolisms that were very different to those of other dinosaurs, perhaps intermediate between mammals and reptiles. New studies published by Taia Wyenberg-henzler in 2022 suggest that sauropods in North America declined due to undetermined reasons in regards to their niches and distribution during the end of the Jurassic and into the latest Cretaceous. Why this is remains unclear, but some similarities in feeding niches between iguanodontians, hadrosauroids and sauropods have been suggested and may have resulted in some competition. However, this cannot fully explain the full decline in distribution of sauropods, as competitive exclusion would have resulted in a much more rapid decline than what is shown in the fossil record. Moreover, it must be determined as to whether sauropod declines in North America was the result of a change in preferred flora that sauropods ate, climate, or other factors. It is also suggested in this same study that iguanodontians and hadrosauroids took advantage of recently vacated niches left by a decline in sauropod diversity during the late Jurassic and the Cretaceous in North America.
Herding and parental care
Many lines of fossil evidence, from both bone beds and trackways, indicate that sauropods were gregarious animals that formed herd
A herd is a social group of certain animals of the same species, either wild or domestic. The form of collective animal behavior associated with this is called ''herding''. These animals are known as gregarious animals.
The term ''herd'' is ...
s. However, the makeup of the herds varied between species. Some bone beds, for example a site from the Middle Jurassic
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations co ...
of Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
, appear to show herds made up of individuals of various age groups, mixing juveniles and adults. However, a number of other fossil sites and trackways indicate that many sauropod species travelled in herds segregated by age, with juveniles forming herds separate from adults. Such segregated herding strategies have been found in species such as ''Alamosaurus
''Alamosaurus'' (; meaning "Ojo Alamo lizard") is a genus of opisthocoelicaudiine titanosaurian sauropod dinosaurs, containing a single known species, ''Alamosaurus sanjuanensis'', from the late Cretaceous Period of what is now southern North Am ...
'', ''Bellusaurus
''Bellusaurus'' (meaning "Beautiful lizard", from Vulgar Latin ''bellus'' 'beautiful' ( masculine form) and Ancient Greek ''sauros'' 'lizard') was a small short-necked sauropod dinosaur from the Middle Jurassic which measured about long. Its f ...
'' and some diplodocids
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 ...
.
In a review of the evidence for various herd types, Myers and Fiorillo attempted to explain why sauropods appear to have often formed segregated herds. Studies of microscopic tooth wear show that juvenile sauropods had diets that differed from their adult counterparts, so herding together would not have been as productive as herding separately, where individual herd members could forage in a coordinated way. The vast size difference between juveniles and adults may also have played a part in the different feeding and herding strategies.
Since the segregation of juveniles and adults must have taken place soon after hatching, and combined with the fact that sauropod hatchlings were most likely precocial
In biology, altricial species are those in which the young are underdeveloped at the time of birth, but with the aid of their parents mature after birth. Precocial species are those in which the young are relatively mature and mobile from the mome ...
, Myers and Fiorillo concluded that species with age-segregated herds would not have exhibited much parental care. On the other hand, scientists who have studied age-mixed sauropod herds suggested that these species may have cared for their young for an extended period of time before the young reached adulthood. A 2014 study suggested that the time from laying the egg to the time of the hatching was likely to have been between 65 and 82 days. Exactly how segregated versus age-mixed herding varied across different groups of sauropods is unknown. Further examples of gregarious behavior will need to be discovered from more sauropod species to begin detecting possible patterns of distribution.
Rearing stance
Since early in the history of their study, scientists, such as Osborn, have speculated that sauropods could rear up on their hind legs, using the tail as the third 'leg' of a tripod. A skeletal mount depicting the diplodocid ''Barosaurus lentus
''Barosaurus'' ( ) was a giant, long-tailed, long-necked, plant-eating sauropod dinosaur closely related to the more familiar ''Diplodocus''. Remains have been found in the Morrison Formation from the Upper Jurassic Period of Utah and South ...
'' rearing up on its hind legs at the American Museum of Natural History
The American Museum of Natural History (abbreviated as AMNH) is a natural history museum on the Upper West Side of Manhattan in New York City. In Theodore Roosevelt Park, across the street from Central Park, the museum complex comprises 26 inter ...
is one illustration of this hypothesis. In a 2005 paper, Rothschild and Molnar reasoned that if sauropods had adopted a bipedal posture at times, there would be evidence of stress fractures in the forelimb 'hands'. However, none were found after they examined a large number of sauropod skeletons.
Heinrich Mallison (in 2009) was the first to study the physical potential for various sauropods to rear into a tripodal stance. Mallison found that some characters previously linked to rearing adaptations were actually unrelated (such as the wide-set hip bones of 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 th ...
s) or would have hindered rearing. For example, titanosaurs had an unusually flexible backbone, which would have decreased stability in a tripodal posture and would have put more strain on the muscles. Likewise, it is unlikely that brachiosaurids could rear up onto the hind legs, as their center of gravity was much farther forward than other sauropods, which would cause such a stance to be unstable.[Mallison, H. (2009). "Rearing for food? Kinetic/dynamic modeling of bipedal/tripodal poses in sauropod dinosaurs". P. 63 in Godefroit, P. and Lambert, O. (eds), ''Tribute to Charles Darwin and Bernissart Iguanodons: New Perspectives on Vertebrate Evolution and Early Cretaceous Ecosystems''. Brussels.]
Diplodocids, on the other hand, appear to have been well adapted for rearing up into a tripodal stance. Diplodocids had a center of mass directly over the hips, giving them greater balance on two legs. Diplodocids also had the most mobile necks of sauropods, a well-muscled pelvic girdle, and tail vertebrae with a specialised shape that would allow the tail to bear weight at the point it touched the ground. Mallison concluded that diplodocids were better adapted to rearing than elephant
Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantidae an ...
s, which do so occasionally in the wild. He also argues that stress fractures in the wild do not occur from everyday behaviour, such as feeding-related activities (contra Rothschild and Molnar).[
]
Head and neck posture
There is little agreement over how sauropods held their heads and necks, and the postures they could achieve in life.
Whether sauropods' long necks could be used for browsing high trees has been questioned based on calculations suggesting that just pumping blood up to the head in such a posture for long would have used some half of its energy intake. Further, to move blood to such a height—dismissing posited auxiliary hearts in the neck—would require a heart 15 times as large as of a similar-sized whale.
The above have been used to argue that the long neck must instead have been held more or less horizontally, presumed to enable feeding on plants over a wide area with less need to move about, yielding a large energy saving for such a large animal. Reconstructions of the necks of ''Diplodocus'' and ''Apatosaurus'' have therefore often portrayed them in near-horizontal, so-called "neutral, undeflected posture".
However, research on living animals demonstrates that almost all extant tetrapod
Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct theraps ...
s hold the base of their necks sharply flexed when alert, showing that any inference from bones about habitual "neutral postures" is deeply unreliable. Meanwhile, computer modeling of ostrich
Ostriches are large flightless birds of the genus ''Struthio'' in the order Struthioniformes, part of the infra-class Palaeognathae, a diverse group of flightless birds also known as ratites that includes the emus, rheas, and kiwis. There are ...
necks has raised doubts over the flexibility needed for stationary grazing.
Trackways and locomotion
Sauropod trackway
Historic roads (historic trails in USA and Canada) are paths or routes that have historical importance due to their use over a period of time. Examples exist from prehistoric times until the early 20th century. They include ancient trackway ...
s and other fossil footprints
A fossil track or ichnite (Ancient Greek, Greek "''ιχνιον''" (''ichnion'') – a track, trace or footstep) is a fossilized footprint. This is a type of trace fossil. A fossil trackway is a sequence of fossil tracks left by a single organism ...
(known as "ichnites") are known from abundant evidence present on most continents. Ichnites have helped support other biological hypotheses about sauropods, including general fore and hind foot anatomy (see ''Limbs and feet'' above). Generally, prints from the forefeet are much smaller than the hind feet, and often crescent-shaped. Occasionally ichnites preserve traces of the claws, and help confirm which sauropod groups lost claws or even digits on their forefeet.
Sauropod tracks from the Villar del Arzobispo Formation
The Villar del Arzobispo Formation is a Late Jurassic to possibly Early Cretaceous geologic formation in eastern Spain. It is equivalent in age to the Lourinhã Formation of Portugal. It was originally thought to date from the Late Tithonian-Middl ...
of early Berriasian
In the geological timescale, the Berriasian is an age/stage of the Early/Lower Cretaceous. It is the oldest subdivision in the entire Cretaceous. It has been taken to span the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years ago) ...
age in Spain support the gregarious behaviour of the group. The tracks are possibly more similar to '' Sauropodichnus giganteus'' than any other ichnogenera, although they have been suggested to be from a basal titanosauriform. The tracks are wide-gauge, and the grouping as close to '' Sauropodichnus'' is also supported by the manus-to-pes distance, the morphology of the manus being kidney bean-shaped, and the morphology of the pes being subtriangular. It cannot be identified whether the footprints of the herd were caused by juveniles or adults, because of the lack of previous trackway individual age identification.
Generally, sauropod trackways are divided into three categories based on the distance between opposite limbs: narrow gauge, medium gauge, and wide gauge. The gauge of the trackway can help determine how wide-set the limbs of various sauropods were and how this may have impacted the way they walked. A 2004 study by Day and colleagues found that a general pattern could be found among groups of advanced sauropods, with each sauropod family being characterised by certain trackway gauges. They found that most sauropods other than 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 th ...
s had narrow-gauge limbs, with strong impressions of the large thumb claw on the forefeet. Medium gauge trackways with claw impressions on the forefeet probably belong to brachiosaurids and other primitive titanosauriformes
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 ...
, which were evolving wider-set limbs but retained their claws. Primitive true titanosaurs also retained their forefoot claw but had evolved fully wide gauge limbs. Wide gauge limbs were retained by advanced titanosaurs, trackways from which show a wide gauge and lack of any claws or digits on the forefeet.
Occasionally, only trackways from the forefeet are found. Falkingham ''et al.'' used computer modelling to show that this could be due to the properties of the substrate. These need to be just right to preserve tracks. Differences in hind limb and fore limb surface area, and therefore contact pressure with the substrate, may sometimes lead to only the forefeet trackways being preserved.
Biomechanics and speed
In a study published in PLoS ONE on October 30, 2013, by Bill Sellers, Rodolfo Coria
Rodolfo Aníbal Coria (born in Neuquén June 1, 1959), is an Argentine paleontologist.
He is best known for having directed the field study and co-naming of ''Argentinosaurus'' (possibly the world's largest land animal ever) in 1993, and ''Gigano ...
, Lee Margetts ''et al.'', ''Argentinosaurus
''Argentinosaurus'' is a genus of giant sauropod dinosaur that lived during the Late Cretaceous period in what is now Argentina. Although it is only known from fragmentary remains, ''Argentinosaurus'' is one of the largest known land animals o ...
'' was digitally reconstructed to test its locomotion for the first time. Before the study, the most common way of estimating speed was through studying bone histology
Histology,
also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures vis ...
and ichnology. Commonly, studies about sauropod bone histology and speed focus on the postcranial skeleton, which holds many unique features, such as an enlarged process on the ulna
The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...
, a wide lobe on the ilia, an inward-slanting top third of the femur
The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...
, and an extremely ovoid femur shaft. Those features are useful when attempting to explain trackway patterns of graviportal animals. When studying ichnology to calculate sauropod speed, there are a few problems, such as only providing estimates for certain gaits because of preservation bias, and being subject to many more accuracy problems.
To estimate the gait and speed of ''Argentinosaurus'', the study performed a musculoskeletal analysis. The only previous musculoskeletal analyses were conducted on hominoids
Apes (collectively Hominoidea ) are a clade of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and as well as Europe in prehistory), which together with its siste ...
, terror bird
Phorusrhacids, colloquially known as terror birds, are an extinct clade of large carnivorous flightless birds that were one of the largest species of apex predators in South America during the Cenozoic era; their conventionally accepted temporal ...
s, and other dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s. Before they could conduct the analysis, the team had to create a digital skeleton of the animal in question, show where there would be muscle layering, locate the muscles and joints, and finally find the muscle properties before finding the gait and speed. The results of the biomechanics study revealed that ''Argentinosaurus'' was mechanically competent at a top speed of 2 m/s (5 mph) given the great weight of the animal and the strain that its joints were capable of bearing. The results further revealed that much larger terrestrial vertebrates might be possible, but would require significant body remodeling and possible sufficient behavioral change to prevent joint collapse.
Body size
Sauropods were gigantic descendants of surprisingly small ancestors. Basal dinosauriformes, such as ''Pseudolagosuchus
''Lewisuchus'' is a genus of archosaur that lived during the Late Triassic (early Carnian). As a silesaurid dinosauriform, it was a member of the group of reptiles most commonly considered to be the closest relatives of dinosaurs (possibly tr ...
'' and ''Marasuchus
''Marasuchus'' (meaning "Mara crocodile") is a genus of basal dinosauriform archosaur which is possibly synonymous with '' Lagosuchus''. Both genera lived during the Late Triassic in what is now La Rioja Province, Argentina. ''Marasuchus'' conta ...
'' from the Middle Triassic of Argentina, weighed approximately or less. These evolved into saurischia, which saw a rapid increase of bauplan
A body plan, ( ), or ground plan is a set of morphological features common to many members of a phylum of animals. The vertebrates share one body plan, while invertebrates have many.
This term, usually applied to animals, envisages a "bluepr ...
size, although more primitive members like ''Eoraptor
''Eoraptor'' () is a genus of small, lightly built, basal sauropodomorph. One of the earliest-known dinosaurs, it lived approximately 231 to 228 million years ago, during the Late Triassic in Western Gondwana, in the region that is now northwest ...
'', ''Panphagia
''Panphagia'' is a genus of sauropodomorph dinosaur described in 2009. It lived around 231 million years ago, during the Carnian age of the Late Triassic period in what is now northwestern Argentina. Fossils of the genus were found in the La ...
'', ''Pantydraco
''Pantydraco'' (where "panty-" is short for Pant-y-ffynnon, signifying ''hollow of the spring/well'' in Welsh, referring to the quarry at Bonvilston in South Wales where it was found) was a genus of basal sauropodomorph dinosaur from the Late Tri ...
'', ''Saturnalia
Saturnalia is an ancient Roman festival and holiday in honour of the god Saturn, held on 17 December of the Julian calendar and later expanded with festivities through to 23 December. The holiday was celebrated with a sacrifice at the Temple ...
'' and ''Guaibasaurus
''Guaibasaurus'' is an extinct genus of basal saurischian dinosaur known from the Late Triassic Caturrita Formation of Rio Grande do Sul, southern Brazil. Most analyses recover it as a sauropodomorph, although there are some suggestions that it ...
'' still retained a moderate size, possibly under . Even with these small, primitive forms, there is a notable size increase among sauropodomorphs, although scanty remains of this period make interpretation conjectural. There is one definite example of a small derived sauropodomorph: ''Anchisaurus
''Anchisaurus'' is a genus of basal sauropodomorph dinosaur. It lived during the Early Jurassic Period, and its fossils have been found in the red sandstone of the Portland Formation, Northeastern United States, which was deposited from the He ...
'', under , even though it is closer to the sauropods than ''Plateosaurus
''Plateosaurus'' (probably meaning "broad lizard", often mistranslated as "flat lizard") is a genus of plateosaurid dinosaur that lived during the Late Triassic period, around 214 to 204 million years ago, in what is now Central and Northern Eur ...
'' and '' Riojasaurus'', which were upwards of in weight.
Evolving from sauropodomorphs, the sauropods were huge. Their giant size probably resulted from an increased growth rate made possible by tachymetabolic endothermy, a trait which evolved in sauropodomorphs. Once branched into sauropods, sauropodomorphs continued steadily to grow larger, with smaller sauropods, like the Early Jurassic ''Barapasaurus
''Barapasaurus'' ( ) is a genus of basal sauropod dinosaur from Early Jurassic rocks of India. The only species is ''B. tagorei''. ''Barapasaurus'' comes from the lower part of the Kota Formation, that dates back to the Sinemurian and Pliensb ...
'' and ''Kotasaurus
''Kotasaurus'' ( ; meaning " Kota Formation lizard") is a genus of sauropod dinosaur from the Early Jurassic period ( Sinemurian–Pliensbachian). The only known species is ''Kotasaurus yamanpalliensis''. It was discovered in the Kota Formation ...
'', evolving into even larger forms like the Middle Jurassic ''Mamenchisaurus
''Mamenchisaurus'' (or spelling pronunciation ) is a genus of sauropod dinosaur known for their remarkably long necks which made up nearly half the total body length. Numerous species have been assigned to the genus; however, many of these might ...
'' and ''Patagosaurus
''Patagosaurus'' (meaning "Patagonia lizard") is an extinct genus of eusauropod dinosaur from the Middle-Late Toarcian of Patagonia, Argentina. It was first found in deposits of the Cañadón Asfalto Formation, which date to around 179 to 177&n ...
''. Responding to the growth of sauropods, their theropod predators grew also, as shown by an ''Allosaurus
''Allosaurus'' () is a genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic epoch (Kimmeridgian to late Tithonian). The name "''Allosaurus''" means "different lizard" alluding to ...
''-sized coelophysoid
Coelophysoidea were common dinosaurs of the Late Triassic and Early Jurassic periods. They were widespread geographically, probably living on all continents. Coelophysoids were all slender, carnivorous forms with a superficial similarity to the ...
from Germany
Germany,, officially the Federal Republic of Germany, is a country in Central Europe. It is the second most populous country in Europe after Russia, and the most populous member state of the European Union. Germany is situated betwe ...
.
Size in Neosauropoda
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 ...
is quite plausibly the clade of dinosaurs with the largest body sizes ever to have existed. The few exceptions of smaller size are hypothesized to be caused by island dwarfism
Insular dwarfism, a form of phyletic dwarfism, is the process and condition of large animals evolving or having a reduced body size when their population's range is limited to a small environment, primarily islands. This natural process is disti ...
, although there is a trend in Titanosauria
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 ...
towards a smaller size. The titanosaurs, however, were some of the largest sauropods ever. Other than titanosaurs, a clade of diplodocoids, a group of giants, called Dicraeosauridae
Dicraeosauridae is a family of diplodocoid sauropods who are the sister group to Diplodocidae. Dicraeosaurids are a part of the Flagellicaudata, along with Diplodocidae. Dicraeosauridae includes genera such as '' Amargasaurus'', '' Suuwassea' ...
, is identified by a small body size. No sauropods were very small, however, for even "dwarf" sauropods are larger than , a size reached by only about 10% of all mammalian species.
Independent gigantism
Although in general, sauropods were large, a gigantic size ( or more) was reached independently at multiple times in their evolution. Many gigantic forms existed in the Late Jurassic (specifically Kimmeridgian
In the geologic timescale, the Kimmeridgian is an age in the Late Jurassic Epoch and a stage in the Upper Jurassic Series. It spans the time between 157.3 ± 1.0 Ma and 152.1 ± 0.9 Ma (million years ago). The Kimmeridgian follows the Oxfordian ...
and Turonian
The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded by t ...
), such as the turiasaur ''Turiasaurus
''Turiasaurus'' (meaning " Turia lizard") is a genus of sauropod dinosaurs. It is known from a single fossil specimen representing the species ''Turiasaurus riodevensis'', found in the Kimmeridgian Villar del Arzobispo Formation of Teruel, Spain ...
'' and the diplodocoids ''Maraapunisaurus
''Maraapunisaurus'' is a genus of sauropod dinosaur from the Late Jurassic Morrison Formation of western North America. It is known only from what has sometimes been estimated to be the largest dinosaur specimen ever discovered, originally name ...
'', ''Diplodocus
''Diplodocus'' (, , or ) was a genus of diplodocid sauropod dinosaurs, whose fossils were first discovered in 1877 by S. W. Williston. The generic name, coined by Othniel Charles Marsh in 1878, is a neo-Latin term derived from Greek διπ ...
'' and ''Barosaurus
''Barosaurus'' ( ) was a giant, long-tailed, long-necked, plant-eating sauropod dinosaur closely related to the more familiar ''Diplodocus''. Remains have been found in the Morrison Formation from the Upper Jurassic Period of Utah and South Da ...
''. Through the Early to Late Cretaceous, the giants ''Sauroposeidon
''Sauroposeidon'' ( ; meaning "lizard earthquake god", after the Greek god Poseidon) is a genus of sauropod dinosaur known from several incomplete specimens including a bone bed and fossilized trackways that have been found in the U.S. states of ...
'', ''Paralititan
''Paralititan'' (meaning "tidal giant") was a giant titanosaurian sauropod dinosaur genus discovered in coastal deposits in the Upper Cretaceous Bahariya Formation of Egypt. It lived between 99.6 and 93.5 million years ago.Holtz, Thomas R. Jr. (2 ...
'', ''Argentinosaurus
''Argentinosaurus'' is a genus of giant sauropod dinosaur that lived during the Late Cretaceous period in what is now Argentina. Although it is only known from fragmentary remains, ''Argentinosaurus'' is one of the largest known land animals o ...
'', ''Puertasaurus
''Puertasaurus'' is a genus of sauropod dinosaur that lived in South America during the Late Cretaceous Period. It is known from a single specimen recovered from sedimentary rocks of the Cerro Fortaleza Formation in southwestern Patagonia, Ar ...
'', ''Antarctosaurus
''Antarctosaurus'' (; meaning "southern lizard") is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period of what is now South America. The type species, ''Antarctosaurus wichmannianus'', and a second species, ''Antarctosau ...
giganteus'', ''Dreadnoughtus
''Dreadnoughtus'' is a genus of titanosaurian sauropod dinosaur containing a single species, ''Dreadnoughtus schrani''. ''D. schrani'' is known from two partial skeletons discovered in Upper Cretaceous (Campanian to Maastrichtian; approximately ...
schrani'', ''Notocolossus
''Notocolossus'' is a genus of titanosaurian sauropod dinosaur from late Cretaceous strata of Mendoza Province, Argentina.
Discovery and naming
A fossil of a large sauropod was discovered by the Argentine paleontologist Dr. Bernardo Javier ...
'' and '' Futalognkosaurus'' lived, with all possibly being titanosaurs. One sparsely known possible giant is ''Huanghetitan
''Huanghetitan'' (meaning "Yellow River titan"), is a genus of sauropod dinosaur from the early Cretaceous Period. It was a basal titanosauriform which lived in what is now Gansu, China.
History
The type species, ''Huanghetitan liujiaxiaens ...
ruyangensis'', only known from long ribs. These giant species lived in the Late Jurassic to the Late Cretaceous, appearing independently over a time span of 85 million years.
Insular dwarfism in sauropods
Two well-known island dwarf species of sauropods are the Cretaceous ''Magyarosaurus
''Magyarosaurus'' (" Magyar lizard") is a genus of dwarf sauropod dinosaur from late Cretaceous Period (early to late Maastrichtian) in Romania. It is one of the smallest-known adult sauropods, measuring only in length and in body mass. The t ...
'' (at one point its identity as a dwarf was challenged) and the Jurassic '' Europasaurus'', both from Europe. Even though these sauropods are small, the only way to prove they are true dwarfs is through a study of their bone histology. A study by Martin Sander and colleagues in 2006 examined eleven individuals of ''Europasaurus holgeri'' using bone histology and demonstrated that the small island species evolved through a decrease in the growth rate of long bones as compared to rates of growth in ancestral species on the mainland. Two other possible dwarfs are ''Rapetosaurus
''Rapetosaurus'' ( ) is a genus of titanosaurian sauropod dinosaur that lived in Madagascar from 70 to 66 million years ago, at the end of the Cretaceous Period. Only one species, ''Rapetosaurus krausei'', has been identified.
Like other sauropod ...
'', which existed on the island of Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
, an isolated island in the Cretaceous, and ''Ampelosaurus
''Ampelosaurus'' ( ; meaning "vine lizard") is a titanosaurian sauropod dinosaur from the Late Cretaceous Period of what is now France. Its type species is ''A. atacis'', named by Le Loeuff in 1995. A possible unnamed species has given ''Ampel ...
'', a titanosaur that lived on the Iberian peninsula of southern Spain and France. ''Amanzia
''Amanzia'' (after Swiss geologist Amanz Gressly) is a genus of turiasaurian sauropod dinosaur from the Reuchenette Formation in Moutier, Switzerland. The type and only species is ''Amanzia greppini'', originally named as a species of ''Orni ...
'' from Switzerland might also be a dwarf, but this has yet to be proven. One of the most extreme cases of island dwarfism is found in '' Europasaurus'', a relative of the much larger '' Camarasaurus'' and ''Brachiosaurus
''Brachiosaurus'' () is a genus of sauropod dinosaur that lived in North America during the Late Jurassic, about 154to 150million years ago. It was first described by American paleontologist Elmer S. Riggs in 1903 from fossils found in th ...
'': it was only about long, an identifying trait of the species. As for all dwarf species, their reduced growth rate led to their small size.
Paleopathology
Sauropods are rarely known for preserved injuries or signs of illnesses, but more recent discoveries show they could suffer from such pathologies. A diplodocid specimen from the Morrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic, Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandsto ...
referred to as "Dolly" was described in 2022 with evidence of a severe respiratory infection. Sauropod ribs from Yunyang County
Yunyang County () is a county in the northeast of Chongqing Municipality, China, bordering Hubei province to the south.
In eastern Chongqing is Yunyang County with over 1,400 years of history and a reputation as the 'Bright Pearl of Chongqing'. ...
, Chongqing
Chongqing ( or ; ; Sichuanese dialects, Sichuanese pronunciation: , Standard Mandarin pronunciation: ), Postal Romanization, alternately romanized as Chungking (), is a Direct-administered municipalities of China, municipality in Southwes ...
, in southwest China show evidence of rib breakage by way of traumatic fracture, bone infection, and osteosclerosis
Osteosclerosis is a disorder that is characterized by abnormal hardening of bone and an elevation in bone density. It may predominantly affect the medullary portion and/or cortex of bone. Plain radiographs are a valuable tool for detecting and ...
.
History of discovery
The first scraps of fossil remains now recognized as sauropods all came from England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
and were originally interpreted in a variety of different ways. Their relationship to other dinosaurs was not recognized until well after their initial discovery.
The first sauropod fossil to be scientifically described was a single tooth known by the non- Linnaean descriptor '' Rutellum implicatum''. This fossil was described by Edward Lhuyd
Edward Lhuyd FRS (; occasionally written Llwyd in line with modern Welsh orthography, 1660 – 30 June 1709) was a Welsh naturalist, botanist, linguist, geographer and antiquary. He is also named in a Latinate form as Eduardus Luidius.
Life
...
in 1699, but was not recognized as a giant prehistoric reptile at the time.[Lhuyd, E. (1699). ''Lithophylacii Britannici Ichnographia, sive lapidium aliorumque fossilium Britannicorum singulari figura insignium''. Gleditsch and Weidmann: London.] Dinosaurs would not be recognized as a group until over a century later.
Richard Owen
Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomist and paleontologist. Owen is generally considered to have been an outstanding naturalist with a remarkable gift for interpreting fossils.
Owe ...
published the first modern scientific descriptions of sauropods in 1841, in a book and a paper naming ''Cardiodon
''Cardiodon'' (meaning "heart tooth", in reference to the shape) was a herbivorous genus of sauropod dinosaur, based on a tooth from the late Bathonian-age Middle Jurassic Forest Marble Formation of Wiltshire, England. Historically, it is very o ...
'' and ''Cetiosaurus
''Cetiosaurus'' () meaning 'whale lizard', from the Greek '/ meaning 'sea monster' (later, 'whale') and '/ meaning 'lizard', is a genus of herbivorous sauropod dinosaur from the Middle Jurassic Period, living about 168 million years ago in what ...
''. ''Cardiodon'' was known only from two unusual, heart-shaped teeth (from which it got its name), which could not be identified beyond the fact that they came from a previously unknown large reptile
Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...
. ''Cetiosaurus'' was known from slightly better, but still scrappy remains. Owen thought at the time that ''Cetiosaurus'' was a giant marine reptile related to modern crocodile
Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to inclu ...
s, hence its name, which means "whale lizard". A year later, when Owen coined the name Dinosauria, he did not include ''Cetiosaurus'' and ''Cardiodon'' in that group.[Owen, R. (1842). "Report on British Fossil Reptiles". Part II. Report of the British Association for the Advancement of Science, Plymouth, England.]
In 1850, Gideon Mantell
Gideon Algernon Mantell MRCS FRS (3 February 1790 – 10 November 1852) was a British obstetrician, geologist and palaeontologist. His attempts to reconstruct the structure and life of ''Iguanodon'' began the scientific study of dinosaurs: in ...
recognized the dinosaurian nature of several bones assigned to ''Cetiosaurus'' by Owen. Mantell noticed that the leg bones contained a medullary cavity
The medullary cavity (''medulla'', innermost part) is the central cavity of bone shafts where red bone marrow and/or yellow bone marrow (adipose tissue) is stored; hence, the medullary cavity is also known as the marrow cavity.
Located in the m ...
, a characteristic of land animals. He assigned these specimens to the new genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
''Pelorosaurus
''Pelorosaurus'' ( ; meaning "monstrous lizard") is a genus of titanosauriform sauropod dinosaur. Remains referred to ''Pelorosaurus'' date from the Early Cretaceous period, about 140-125 million years ago, and have been found in England and Port ...
'', and grouped it together with the dinosaurs. However, Mantell still did not recognize the relationship to ''Cetiosaurus''.
The next sauropod find to be described and misidentified as something other than a dinosaur were a set of hip vertebrae described by Harry Seeley
Harry Govier Seeley (18 February 1839 – 8 January 1909) was a British paleontologist.
Early life
Seeley was born in London on 18 February 1839, the second son of Richard Hovill Seeley, a goldsmith, and his second wife Mary Govier. When his fat ...
in 1870. Seeley found that the vertebrae were very lightly constructed for their size and contained openings for air sacs
Air sacs are spaces within an organism where there is the constant presence of air. Among modern animals, birds possess the most air sacs (9–11), with their extinct dinosaurian relatives showing a great increase in the pneumatization (presence ...
(''pneumatization''). Such air sacs were at the time known only in bird
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
s and pterosaur
Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 to ...
s, and Seeley considered the vertebrae to come from a pterosaur. He named the new genus ''Ornithopsis
''Ornithopsis'' (meaning "bird-likeness") was a medium-sized Early Cretaceous sauropod dinosaur, from England. The type species, which is the only species seen as valid today, is ''O. hulkei''.
History of discovery
Gideon Algernon Mantell descr ...
'', or "bird face" because of this.
When more complete specimens of ''Cetiosaurus'' were described by Phillips in 1871, he finally recognized the animal as a dinosaur related to ''Pelorosaurus''.[Phillips, J. (1871). ''Geology of Oxford and the Valley of the Thames.'' Oxford: Clarendon Press, 523 pp.] However, it was not until the description of new, nearly complete sauropod skeletons from the United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
(representing ''Apatosaurus
''Apatosaurus'' (; meaning "deceptive lizard") is a genus of herbivorous sauropod dinosaur that lived in North America during the Late Jurassic period. Othniel Charles Marsh described and named the first-known species, ''A. ajax'', in 1877, an ...
'' and '' Camarasaurus'') later that year that a complete picture of sauropods emerged. An approximate reconstruction of a complete sauropod skeleton was produced by artist John A. Ryder, hired by paleontologist E.D. Cope, based on the remains of ''Camarasaurus'', though many features were still inaccurate or incomplete according to later finds and biomechanical studies.[Osborn, H.F., and Mook, C.C. (1921). "''Camarasaurus'', ''Amphicoelias'' and other sauropods of Cope". ''Memoirs of the American Museum of Natural History'', n.s. 3:247-387 and plates LX-LXXXV.] Also in 1877, Richard Lydekker
Richard Lydekker (; 25 July 1849 – 16 April 1915) was an English naturalist, geologist and writer of numerous books on natural history.
Biography
Richard Lydekker was born at Tavistock Square in London. His father was Gerard Wolfe Lydekker, ...
named another relative of ''Cetiosaurus'', ''Titanosaurus
''Titanosaurus'' (; ) is a dubious genus of sauropod dinosaurs, first described by Richard Lydekker in 1877.R. Lydekker. (1877). Notices of new and other Vertebrata from Indian Tertiary and Secondary rocks. ''Records of the Geological Survey of I ...
'', based on an isolated vertebra.
In 1878, the most complete sauropod yet was found and described by Othniel Charles Marsh
Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of Paleontology in Yale College and President of the National Academy of Sciences. He was one of the preeminent scientists in the field of paleontology. Among h ...
, who named it ''Diplodocus
''Diplodocus'' (, , or ) was a genus of diplodocid sauropod dinosaurs, whose fossils were first discovered in 1877 by S. W. Williston. The generic name, coined by Othniel Charles Marsh in 1878, is a neo-Latin term derived from Greek διπ ...
''. With this find, Marsh also created a new group to contain ''Diplodocus'', ''Cetiosaurus'', and their increasing roster of relatives to differentiate them from the other major groups of dinosaurs. Marsh named this group Sauropoda, or "lizard feet".
Classification
The first phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
definition of Sauropoda was published in 1997 by Salgado and colleagues. They defined the clade as a node-based taxon
Phylogenetic nomenclature is a method of nomenclature for taxa in biology that uses phylogenetic definitions for taxon names as explained below. This contrasts with the traditional approach, in which taxon names are defined by a '' type'', which ...
, containing "the most recent common ancestor
In biology and genetic genealogy, the most recent common ancestor (MRCA), also known as the last common ancestor (LCA) or concestor, of a set of organisms is the most recent individual from which all the organisms of the set are descended. The ...
of ''Vulcanodon karibaensis'' and Eusauropoda and all of its descendants". Later, several stem-based definitions were proposed, including one by Yates (2007), who defined Sauropoda as "the most inclusive clade that includes ''Saltasaurus loricatus'' but not '' Melanorosaurus readi''". Proponents of this definition also use the clade name Gravisauria
Gravisauria is a clade of sauropod dinosaurs consisting of some genera, Vulcanodontidae and Eusauropoda.Allain, R. and Aquesbi, N. (2008). "Anatomy and phylogenetic relationships of ''Tazoudasaurus naimi'' (Dinosauria, Sauropoda) from the late Ea ...
, defined as the most recent ancestor of '' Tazoudasaurus naimi'' and ''Saltasaurus loricatus'' and all of its descendants for the clade equivalent to Sauropoda as defined by Salgado ''et al.''
The phylogenetic relationships of the sauropods have largely stabilised in recent years, though there are still some uncertainties, such as the placement of ''Euhelopus
''Euhelopus'' is a genus of sauropod dinosaur that lived between 145 and 133 million years ago during the Berriasian and Valanginian stages of the Early Cretaceous in what is now Shandong Province in China. It was a large quadrupedal herbivore. U ...
'', ''Haplocanthosaurus
''Haplocanthosaurus'' (meaning "simple spined lizard") is a genus of intermediate sauropod dinosaur. Two species, ''H. delfsi'' and ''H. priscus'', are known from incomplete fossil skeletons. It lived during the late Jurassic period (Kimmeridgia ...
'', '' Jobaria'' and Nemegtosauridae
Nemegtosauridae is a Scientific classification, family of titanosaurian sauropod dinosaurs based on their diplodocidae, diplodocid-like skulls. Only three species are known: ''Nemegtosaurus'', ''Quaesitosaurus'' and possibly ''Tapuiasaurus'', each ...
.
Cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...
after an analysis presented by Sander and colleagues in 2011.
See also
* List of sauropod species
References
See also
*
*
*
{{Taxonbar, from=Q14416
Norian first appearances
Maastrichtian extinctions
Articles containing video clips