Titanosaurs
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Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of
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, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still thriving at the time of the
extinction event An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp fall in the diversity and abundance of multicellular organisms. It occ ...
at the end of the
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 ...
. This group includes some of the largest land animals known to have ever existed, such as ''
Patagotitan ''Patagotitan'' is a genus of titanosaurian sauropoda, sauropod dinosaur from the Cerro Barcino Formation in Chubut Province, Patagonia, Argentina. The genus contains a single species known from at least six young adult individuals, ''Patagotita ...
'', estimated at long with a mass of , and the comparably-sized ''
Argentinosaurus ''Argentinosaurus'' (meaning "lizard from Argentina") is a genus of giant sauropod dinosaur that lived during the Late Cretaceous Period (geology), period in what is now Argentina. Although it is only known from fragmentary remains, ''Argentinos ...
'' and '' Puertasaurus'' from the same region. The group's name alludes to the mythological
Titans In Greek mythology, the Titans ( ; ) were the pre-Twelve Olympians, Olympian gods. According to the ''Theogony'' of Hesiod, they were the twelve children of the primordial parents Uranus (mythology), Uranus (Sky) and Gaia (Earth). The six male ...
of ancient
Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...
, via the type
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
(now considered a ''
nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium,'' it may be impossible to determine whether a ...
)'' ''
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 ...
''. Together with the
brachiosaurids 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 ...
and relatives, titanosaurs make up the larger sauropod
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 ...
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 ...
. Titanosaurs have long been a poorly-known group, and the relationships between titanosaur species are still not well-understood.


Fossil record

Due to the near-global distribution of titanosaurs during the Cretaceous, titanosaur fossils have been found on every continent, including Antarctica. However, titanosaurs have the least complete fossil record of any major sauropodomorph group. No complete titanosaur skeletons are known, and many species are only known from a few bones. Titanosaur skulls are especially rare. Though fragmentary cranial remains are known for several titanosaur genera, nearly complete skulls have been described for only four: ''
Nemegtosaurus ''Nemegtosaurus'' (meaning 'Reptile from the Nemegt') was a sauropod dinosaur from the Late Cretaceous Period of what is now Mongolia. Measuring an estimated long and weighing , it was named after the Nemegt Basin in the Gobi Desert, where the ...
'', ''
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 ...
'', ''
Sarmientosaurus ''Sarmientosaurus'' is a genus of titanosaurian sauropod dinosaur belonging to the Titanosauria. It lived in what is now South America, specifically Argentina, during the Upper Cretaceous Period (geology), Period about 95 million years ago. The ...
'', and ''
Tapuiasaurus ''Tapuiasaurus'' (meaning " Tapuia lizard") is a genus of titanosaur which lived during the Lower Cretaceous period (Aptian age) in what is now Minas Gerais, Brazil. Discovery Its fossils, including a partial skeleton with a nearly complet ...
''. As is the case in most other sauropod groups, there are few titanosaur specimens with complete necks preserving all of the
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 ...
in sequence. Only three complete titanosaur necks are known: the holotype of ''
Futalognkosaurus ''Futalognkosaurus'' ( ; meaning "giant chief lizard") is a genus of titanosaurian dinosaur. The herbivorous ''Futalognkosaurus'' lived approximately 87 million years ago in the Portezuelo Formation, in what is now Argentina, of the Coniacian st ...
'' and two undescribed specimens from Argentina. A fourth specimen, of an unidentified titanosaur from Brazil, preserves a nearly complete neck, with only the
atlas An atlas is a collection of maps; it is typically a bundle of world map, maps of Earth or of a continent or region of Earth. Advances in astronomy have also resulted in atlases of the celestial sphere or of other planets. Atlases have traditio ...
, the tiny vertebra forming the joint between the skull and neck, missing. Only five titanosaur specimens preserve complete, articulated hind feet. This incompleteness is especially significant for giant titanosaurs, which are generally known from disarticulated and fragmentary remains. Titanosaurs are one of the few groups of dinosaurs for which fossil eggs are known. The fossil site of Auca Mahuevo preserves a titanosaur nesting ground. Some titanosaur eggs have been found containing fossil
embryos An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...
, which even preserve fossil skin. These fossil embryos are among the few titanosaur specimens to preserve complete skulls.


Description

Titanosauria have the largest range of body size of any sauropod clade, and includes both the largest known sauropods and some of the smallest. One of the largest titanosaurs, ''
Patagotitan ''Patagotitan'' is a genus of titanosaurian sauropoda, sauropod dinosaur from the Cerro Barcino Formation in Chubut Province, Patagonia, Argentina. The genus contains a single species known from at least six young adult individuals, ''Patagotita ...
'', had a body mass estimated to be , whereas one of the smallest, ''
Magyarosaurus ''Magyarosaurus'' (" Hungarian 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 less than long and weighing less than ...
'', had a body mass of approximately . Even relatively closely related titanosaurs could have very different body sizes, as the small rinconsaurs were closely related to the gigantic lognkosaurs. Fossils from perhaps the largest dinosaur ever found were discovered in 2021 in the Neuquén Province of northwest Patagonia, Argentina. It is believed that they are from a titanosaur. Some of smallest titanosaurs, such as ''
Magyarosaurus ''Magyarosaurus'' (" Hungarian 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 less than long and weighing less than ...
'', inhabited Europe, which was largely made up of islands during the Cretaceous, and were likely island dwarfs. Another taxon of tiny titanosaurs, ''
Ibirania ''Ibirania'' (meaning "Ibirá wanderer" or "tree wanderer") is a genus of dwarf saltasaurine titanosaur dinosaur from the Late Cretaceous (Santonian to Campanian) São José do Rio Preto Formation (Bauru Group, Bauru Basin) of Southeast Brazil. Th ...
'', lived a non-insular context in Upper Creaceous Brazil, and is an example of nanism resultant from other ecological pressures.


Head and neck

The heads of titanosaurs are poorly known. However, several different cranial morphologies are apparent. In some species, such as ''
Sarmientosaurus ''Sarmientosaurus'' is a genus of titanosaurian sauropod dinosaur belonging to the Titanosauria. It lived in what is now South America, specifically Argentina, during the Upper Cretaceous Period (geology), Period about 95 million years ago. The ...
'', the head resembled that of
brachiosaurids 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 ...
. In others, such as ''
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 ...
'' and ''
Nemegtosaurus ''Nemegtosaurus'' (meaning 'Reptile from the Nemegt') was a sauropod dinosaur from the Late Cretaceous Period of what is now Mongolia. Measuring an estimated long and weighing , it was named after the Nemegt Basin in the Gobi Desert, where the ...
'', the head resembled that of
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 hav ...
. In some titanosaurs, the skull was especially diplodocid-like due to square-shaped jaws; the titanosaur ''
Antarctosaurus ''Antarctosaurus'' (; meaning "southern lizard") is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period (geology), Period of what is now South America. The type species, ''Antarctosaurus wichmannianus'', and a second speci ...
'' is especially similar to the
rebbachisaurid Rebbachisauridae is a Family (biology), family of sauropod dinosaurs known from fragmentary fossil remains from the Cretaceous of South America, Africa, North America, Europe and possibly Central Asia. Taxonomy In 1990 sauropod specialist Jack M ...
''
Nigersaurus ''Nigersaurus'' () is a genus of rebbachisaurid sauropod dinosaur that lived during the middle Cretaceous period, about 115 to 105 million years ago. It was discovered in the Elrhaz Formation in an area called Gadoufaoua, in Niger. Fossils o ...
''. Titanosaurs had small heads, even when compared with other sauropods. The head was also wide, similar to the heads 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 ''
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 ...
,'' though somewhat more elongated. Titanosaurian nostrils were large ("
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 ...
n") and all had crests formed by the nasal bones. Their teeth were either somewhat spatulate (spoon-like) or like pegs or pencils, but were always very small. Titanosaur necks were of average length for sauropods, and their
tail The tail is the elongated section at the rear end of a bilaterian animal's body; in general, the term refers to a distinct, flexible appendage extending backwards from the midline of the torso. In vertebrate animals that evolution, evolved to los ...
s were whip-like though not as long as in the
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. While the
pelvis The pelvis (: pelves or pelvises) is the lower part of an Anatomy, anatomical Trunk (anatomy), trunk, between the human abdomen, abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also c ...
was slimmer than some sauropods, the pectoral (chest) area was much wider, giving them a uniquely "wide-legged" stance. As a result, the fossilized trackways of titanosaurs are distinctly broader than other sauropods. Their forelimbs were also stocky, and often longer than their hind limbs. Unlike other sauropods, some titanosaurs had no digits, walking 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. Their
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 (back bones) were solid (not hollowed-out), which may be a reversal to more basal
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 Ornithi ...
n characteristics. Their spinal column was relatively flexible, likely making them more agile than other sauropods, though at the expense of rearing on their hind legs compared to the Diplodocoids. One of the most characteristic features shared by most titanosaurs were their procoelous caudal vertebrae, with ball-and-socket articulations between the vertebral centra.


Torso and limbs

The
dorsal vertebrae In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebra (anatomy), vertebrae of intermediate size between the ce ...
of titanosaurs show multiple derived features among sauropods. Similarly to the Rebbachisauridae, titanosaurs lost the hyposphene-hypantrum articulations, a set of surfaces between vertebrae that prevent additional rotation of the bones. ''
Andesaurus ''Andesaurus'' ( ; "Andes lizard") is a genus of basal titanosaurian sauropod dinosaur which existed during the middle of the Cretaceous Period in South America. Like most sauropods, it would have had a small head on the end of a long neck and a ...
'', one of the most basal titanosaurs, shows a normal hyposphene. The same area is reduced in ''
Argentinosaurus ''Argentinosaurus'' (meaning "lizard from Argentina") is a genus of giant sauropod dinosaur that lived during the Late Cretaceous Period (geology), period in what is now Argentina. Although it is only known from fragmentary remains, ''Argentinos ...
'' to only two ridges, and is fully absent in taxa like ''
Opisthocoelicaudia ''Opisthocoelicaudia'' is a genus of sauropod dinosaur of the Late Cretaceous Period discovered in the Gobi Desert of Mongolia. The type species is ''Opisthocoelicaudia skarzynskii''. A well-preserved skeleton lacking only the head and neck wa ...
'' and ''
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 ...
''. Both ''Argentinosaurus'' and ''
Epachthosaurus ''Epachthosaurus'' (meaning "heavy lizard") was a genus of titanosaurian sauropod dinosaur from the Late Cretaceous. It was a basal Lithostrotia, lithostrotian titanosaur. Its fossils have been found in Central and Northern Patagonia in South Ame ...
'' bear similar intermediate "hyposphenal ridges", which suggests they represent a more primitive form of dorsal vertebrae. Sauropod hands already are highly derived from other dinosaurs, being reduced into columnar
metacarpal 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 ...
s and blocky
phalanges The phalanges (: phalanx ) are digit (anatomy), digital bones in the hands and foot, feet of most vertebrates. In primates, the Thumb, thumbs and Hallux, big toes have two phalanges while the other Digit (anatomy), digits have three phalanges. ...
with fewer claws. However, titanosaurs evolved the manus even further, completely losing the phalanges and heavily modifying the metacarpals. ''
Argyrosaurus ''Argyrosaurus'' ( ) is a genus of titanosaurian sauropod dinosaur that lived about 70 million years ago, during the Late Cretaceous Period (geology), Period of what is now Argentina. Discovery and naming The type species, ''Argyrosaurus superb ...
'' is the only titanosaur known to possess
carpal The carpal bones are the eight small bones that make up the wrist (carpus) that connects the hand to the forearm. The terms "carpus" and "carpal" are derived from the Latin carpus and the Greek καρπός (karpós), meaning "wrist". In huma ...
s. Other taxa like ''Epachthosaurus'' show a reduction of phalanges to one or two bones. ''Opisthoeoclicaudia'' shows even more reduction of the hand than other titanosaurs, with both carpals and phalanges completely absent. However, '' Diamantinasaurus'', while lacking carpals, preserves a manual formula of , including a thumb claw and phalanges on all other digits. This, coupled with the preservation of a single phalanx on digit IV of ''Epachthosaurus'' and potentially ''Opisthocoelicaudia'' (further study is necessary), show that preservation biases may be responsible for the lack of hand phalanges in these taxa. This suggests that ''Alamosaurus'', '' Neuquensaurus'', ''Saltasaurus'' and ''Rapetosaurus -'' all known from imperfect or disarticulated remains previously associated with a lack of phalanges - may have had phalanges but lost them after death. Titanosaurs have a poor fossil record of their pedes (feet), only being complete in five definitive titanosaurs. Among these, '' Notocolossus'' is the largest, and also has the most specialized pes: like all titanosaurs, its pes is composed of short, thick
metatarsal The metatarsal bones or metatarsus (: metatarsi) are a group of five long bones in the midfoot, located between the tarsal bones (which form the heel and the ankle) and the phalanges ( toes). Lacking individual names, the metatarsal bones are ...
s of approximately the same lengths; however, metatarsals I and V are notably more robust than in other taxa.


Integument

From skin impressions found with
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 ...
s, it has been determined that the skin of many titanosaurs was armored with a small mosaic of small, bead-like
scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number ...
surrounding larger scales. While most titanosaurs were very large animals, many were fairly average in size compared to other giant dinosaurs. Some island-dwelling dwarf titanosaurs, such as ''
Magyarosaurus ''Magyarosaurus'' (" Hungarian 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 less than long and weighing less than ...
'', were probably the result of
allopatric speciation Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...
and
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 ...
. Some titanosaurs had
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 amph ...
s. Osteoderms were first confirmed in the genus ''
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 ...
'' but are now known to have been present in a variety of titanosaurs within the clade Lithostrotia. The exact arrangement of osteoderms on the body of a titanosaur is not known, but some paleontologists consider it likely that the osteoderms were arranged in two parallel rows on the animal's back, an arrangement similar to the plates of
stegosaurs Stegosauria is a group of Herbivore, herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous Period (geology), periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere (North America, Europe a ...
. Several other arrangements have been proposed, such as a single row along the midline, and it is possible that different species had different arrangements. The osteoderms were certainly far more sparse than those of
ankylosaurs Ankylosauria is a group of herbivorous dinosaurs of the clade Ornithischia. It includes the great majority of dinosaurs with Armour (zoology), armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short ...
, and did not completely cover the back in scutes. Because of their sparse arrangement, it was unlikely that they served a significant role in defense. However, they may have played an important role in nutrient storage for titanosaurs living in highly seasonal climates and for female titanosaurs laying eggs. Osteoderms were present on both large and small species, so they were not solely used by smaller species as protection against predators. New evidence published in 2021 suggests there were indeed some defensive purposes in titanosaur osteoderms; simulated bite marks from both baurusuchid crocodylomorphs and abelisaurids on titanosaurid osteoderms suggest they could be useful for protecting the animals in addition to functioning in mineral storage.


Classification

Titanosaurs are classified as
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. This highly diverse group forms the dominant clade of Cretaceous sauropods. Within Sauropoda, titanosaurs were once classified as close relatives of
Diplodocidae 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 ...
due to their shared characteristic of narrow teeth, but this is now known to be the result of convergent evolution. Titanosaurs are now known to be most closely related to euhelopodids and
brachiosaurids 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 ...
; together they form a clade named Titanosauriformes. For much of the 20th century, most known species of titanosaurs were classified in the family Titanosauridae, which is no longer in widespread use. Titanosauria was first proposed in 1993 as a taxon to encompass titanosaurids and their close relatives. It has been phylogenetically defined as the clade composed of the most recent common ancestor of ''
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 ...
'' and ''
Andesaurus ''Andesaurus'' ( ; "Andes lizard") is a genus of basal titanosaurian sauropod dinosaur which existed during the middle of the Cretaceous Period in South America. Like most sauropods, it would have had a small head on the end of a long neck and a ...
'' and all of its descendants. The relationships of species within Titanosauria remain largely unresolved, and it is considered one of the most poorly-understood areas of dinosaur classification. One of the few areas of agreement is that the majority of titanosaurs except ''Andesaurus'' and some other basal species form a clade called
Lithostrotia Lithostrotia is a clade of derived titanosaur sauropods that lived during the Early Cretaceous and Late Cretaceous. The group was defined by Upchurch ''et al.'' in 2004 as the most recent common ancestor of ''Malawisaurus'' and ''Saltasaurus'' an ...
, which some researchers consider equivalent to the deprecated Titanosauridae. Lithostrotians include titanosaurs such as ''Alamosaurus'', ''Isisaurus'', ''Malawisaurus'', ''Rapetosaurus'', and ''Saltasaurus''.


Early history

''
Titanosaurus indicus ''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 ...
'' was first named by British
paleontologist Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...
Richard Lydekker Richard Lydekker (; 25 July 1849 – 16 April 1915) was a British naturalist, geologist and writer of numerous books on natural history. He was known for his contributions to zoology, paleontology, and biogeography. He worked extensively in cata ...
in
1877 Events January * January 1 – Queen Victoria is proclaimed Empress of India by the Royal Titles Act 1876, introduced by Benjamin Disraeli, the Prime Minister of the United Kingdom . * January 8 – Great Sioux War of 1876: Batt ...
, as a new taxon of dinosaur based on two caudals and a femur collected on different occasions at the same location in
India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
. While it was later given a position as a sauropod within
Cetiosauridae Cetiosauridae is a family of sauropod dinosaurs which was first proposed by Richard Lydekker in 1888. While traditionally a wastebasket taxon containing various unrelated species, some recent studies have found that it may represent a natural cla ...
by Lydekker in
1888 Events January * January 3 – The great telescope (with an objective lens of diameter) at Lick Observatory in California is first used. * January 12 – The Schoolhouse Blizzard hits Dakota Territory and the states of Montana, M ...
, he named the new
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 ...
family
Titanosauridae Lithostrotia is a clade of derived titanosaur sauropods that lived during the Early Cretaceous and Late Cretaceous. The group was defined by Upchurch ''et al.'' in 2004 as the most recent common ancestor of ''Malawisaurus'' and ''Saltasaurus'' an ...
for the genus in
1893 Events January * January 2 – Webb C. Ball introduces railroad chronometers, which become the general railroad timepiece standards in North America. * January 6 – The Washington National Cathedral is chartered by Congress; th ...
, which included only ''Titanosaurus'' and ''
Argyrosaurus ''Argyrosaurus'' ( ) is a genus of titanosaurian sauropod dinosaur that lived about 70 million years ago, during the Late Cretaceous Period (geology), Period of what is now Argentina. Discovery and naming The type species, ''Argyrosaurus superb ...
'', united by caudals, presacrals, a lack of pleurocoels and open chevrons. Following this, Austro-Hungarian paleontologist
Franz Nopcsa Franz may refer to: People * Franz (given name) * Franz (surname) Places * Franz (crater), a lunar crater * Franz, Ontario, a railway junction and unorganized town in Canada * Franz Lake, in the state of Washington, United States – see Fran ...
reviewed reptile genera in
1928 Events January * January – British bacteriologist Frederick Griffith reports the results of Griffith's experiment, indirectly demonstrating that DNA is the genetic material. * January 1 – Eastern Bloc emigration and defection: Boris B ...
, and provided a short classification of Sauropoda, where he placed the Titanosaurinae (a reranking of Lydekker's Titanosauridae) in
Morosauridae Camarasauridae is a family of sauropod dinosaurs. Among sauropods, camarasaurids are small to medium-sized, with relatively short necks. They are visually identifiable by a short skull with large nares, and broad, spatulate teeth filling a thick ...
, and included the genera ''Titanosaurus'', '' Hypselosaurus'' and ''
Macrurosaurus ''Macrurosaurus'' (meaning "large-tailed lizard") is the name given to a genus of dinosaur from the Early Cretaceous. It was a titanosauriform which lived in what is now England. The type species, ''M. semnus'', was named in 1876. A second speci ...
'' because they all had strongly procoelous caudals. German paleontologist
Friedrich von Huene Baron Friedrich Richard von Hoyningen-Huene (22 March 1875 – 4 April 1969) was a German nobleman paleontologist who described a large number of dinosaurs, more than anyone else in 20th-century Europe. He studied a range of Permo-Carbonife ...
provided a significant revision of Titanosauridae the following year in
1929 This year marked the end of a period known in American history as the Roaring Twenties after the Wall Street Crash of 1929 ushered in a worldwide Great Depression. In the Americas, an agreement was brokered to end the Cristero War, a Catholic ...
, where he reviewed the dinosaurs of
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 ...
Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...
, and named multiple new genera. Huene included multiple species of ''Titanosaurus'' from India,
England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...
,
France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
,
Romania Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...
,
Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...
and Argentina, ''Hypselosaurus'' and '' Aepisaurus'' from France, ''Macrurosaurus'' from England, ''
Alamosaurus ''Alamosaurus'' (; meaning "Ojo Alamo lizard") is a genus of titanosaurian sauropod dinosaurs containing a single known species, ''Alamosaurus sanjuanensis'', from the Maastrichtian age of the Late Cretaceous period in what is now southwestern ...
'' from
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
, and ''Argyrosaurus'', ''
Antarctosaurus ''Antarctosaurus'' (; meaning "southern lizard") is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period (geology), Period of what is now South America. The type species, ''Antarctosaurus wichmannianus'', and a second speci ...
'', and '' Laplatasaurus'' from Argentina. The material between them represented almost all regions of the skeleton, which showed they were derived sauropods Huene interpreted as closest to '' Pleurocoelus'' of the various non-titanosaurid genera. For his
1986 The year 1986 was designated as the International Year of Peace by the United Nations. Events January * January 1 ** Aruba gains increased autonomy from the Netherlands by separating from the Netherlands Antilles. ** Spain and Portugal en ...
thesis, Argentinian paleontologist
Jaime Powell Jaime Eduardo Powell (January 13, 1953 – February 1, 2016) was an Argentine paleontologist who described the titanosaur sauropod dinosaur taxa ''Aeolosaurus'' and found evidence that titanosaurs have osteoderms. Research Powell described the f ...
described and classified many new genera of South American titanosaurs. Using the family Titanosauridae to include them all, he grouped the genera into Titanosaurinae,
Saltasaurinae Saltasaurinae is a subfamily of titanosaurian sauropods known from the late Cretaceous period of South America, India and Madagascar. Description Saltasaurines are relatively small sauropods with the general body shape of a small head, long nec ...
, Antarctosaurinae, Argyrosaurinae and Titanosauridae indet. Titanosaurinae included ''Titanosaurus'' and the new genus ''
Aeolosaurus ''Aeolosaurus'' (; "Aeolus' lizard") is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period (geology), Period of what is now South America. Like most sauropods, it would have been a quadrupedal herbivore with a long neck an ...
'', united by multiple features of the caudal vertebrae; the new clade Saltasaurinae was created to include ''
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 ...
'' and the new genus '' Neuquensaurus'', united by very distinct dorsals, caudals, and ilia; the new clade Antarctosaurinae was created to include ''Antarctosaurus'', distinguished by large size, a different form of
braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, brain-pan, or brainbox, is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calv ...
, more elongate girdle bones, and more robust limb bones; and Argyrosaurinae was created for ''Argyrosaurus'', bearing a more robust forelimb and hand and more primitive dorsals. The new genus ''
Epachthosaurus ''Epachthosaurus'' (meaning "heavy lizard") was a genus of titanosaurian sauropod dinosaur from the Late Cretaceous. It was a basal Lithostrotia, lithostrotian titanosaur. Its fossils have been found in Central and Northern Patagonia in South Ame ...
'' was named for a more basal titanosaurid classified as Titanosauridae indet. along with unnamed specimens, '' Clasmodosaurus'' and ''
Campylodoniscus ''Campylodoniscus'' is a genus of titanosaur sauropod dinosaur from the Late Cretaceous Period of what is now Argentina. The type species was first named and described by Friedrich von Huene in 1929 as ''Campylodon ameghinoi'', the genus name me ...
''.
John Stanton McIntosh John Stanton "Jack" McIntosh ( - ) was an American physicist and paleontologist who heavily influenced the study of sauropods. McIntosh worked professionally as a physicist at Wesleyan University until retirement in 1998, pursuing the study of sa ...
provided a synopsis of sauropod relationships in
1990 Important events of 1990 include the Reunification of Germany and the unification of Yemen, the formal beginning of the Human Genome Project (finished in 2003), the launch of the Hubble Space Telescope, the separation of Namibia from South ...
, using Titanosauridae as the group to contain all taxa like previous authors. ''Opisthocoelicaudia'' was placed in
Opisthocoelicaudiinae Opisthocoelicaudiinae is a subfamily of titanosaurian dinosaurs from the Late Cretaceous. It was named by John McIntosh in 1990. Opisthocoelicaudiines are known from Mongolia, Argentina, and the United States. Two genera were assigned to Opisthoc ...
within
Camarasauridae Camarasauridae is a family of sauropod dinosaurs. Among sauropods, camarasaurids are small to medium-sized, with relatively short necks. They are visually identifiable by a short skull with large nares, and broad, spatulate teeth filling a thick ...
, following its original description and not later works, and ''
Nemegtosaurus ''Nemegtosaurus'' (meaning 'Reptile from the Nemegt') was a sauropod dinosaur from the Late Cretaceous Period of what is now Mongolia. Measuring an estimated long and weighing , it was named after the Nemegt Basin in the Gobi Desert, where the ...
'' and ''
Quaesitosaurus ''Quaesitosaurus'' (meaning "extraordinary lizard") is a genus of nemegtosaurid sauropod containing only the type species, ''Q. orientalis'', described in 1983. It lived from 72 to 71 million years ago during the Late Cretaceous epoch in the Barun ...
'' were placed within
Dicraeosaurinae 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'', '' ...
. Titanosauridae included many previously named genera, plus taxa like ''
Tornieria ''Tornieria'' ("for Gustav Tornier, Tornier") is a genus of diplodocid sauropod dinosaur from the Late Jurassic in Lindi Region of Tanzania. It has a convoluted taxonomy, taxonomic history. Discovery and naming In 1907, German paleontologist E ...
'' and ''
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 convoluted nom ...
''. ''Saltasaurus'' included the species previously known as ''Titanosaurus australis'' and ''T. robustus'', which were named ''Neuquensaurus'' by Powell in 1986. McIntosh provided a large diagnosis of the family: "dorsals with irregularly shaped pleurocoels and spines directed strongly backward; transverse processes directed dorsally as well as laterally, very robust in shoulder region; a second dorsosacral, its rib fused to ilium; caudals strongly procoelous with a prominent ball on distal end of centrum throughout tail; caudal arches on front half of centrum; sternal plates large; preacetabular process of ilium swept outward to become almost horizontal", but stressed that the relationships of titanosaurids to other sauropod groups couldn't be determined due to a lack of cranial material. A brief review of putative titanosaurids from Europe was authored by
Jean Le Loeuff Jean may refer to: People * Jean (female given name) * Jean (male given name) * Jean (surname) Fictional characters * Jean Grey, a Marvel Comics character * Jean Valjean, fictional character in novel ''Les Misérables'' and its adaptations * Jean ...
in
1993 The United Nations General Assembly, General Assembly of the United Nations designated 1993 as: * International Year for the World's Indigenous People The year 1993 in the Kwajalein Atoll in the Marshall Islands had only 364 days, since its ...
, and covered the supposed genera known so far. The
Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 125.77 Ma (million years ago) and 121.4 ± 1.0 Ma (Historically, this stage was placed at 129.4 million to approximately 125 million years ago) It is a ...
(middle Early Cretaceous) species ''Titanosaurus valdensis'', named decades previous by Huene, was kept as the oldest of the titanosaurid and given the new genus name '' Iuticosaurus''. The French taxon ''Aepisaurus'' was removed from the family and placed in undetermined Sauropoda. ''Macrurosaurus'' was considered a
chimaera Chimaeras are Chondrichthyes, cartilaginous fish in the order (biology), order Chimaeriformes (), known informally as ghost sharks, rat fish (not to be confused with rattails), spookfish, or rabbit fish; the last two names are also applied to B ...
of titanosaurid and non-titanosaurid material because of the presence of both procoelous and caudals. Huene's species ''Titanosaurus lydekkeri'' was left as a
nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium,'' it may be impossible to determine whether a ...
, but left within Titanosauridae.
Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...
fossils from France and
Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
were removed from ''Hypselosaurus'' and ''Titanosaurus'', with ''Hypselosaurus'' being declared dubious like ''T. lydekkeri''. The variety of Romanian fossils named as ''Magyarosaurus'' by Huene were also moved into the same species again, ''M. dacus'' as originally named by Nopcsa.


Titanosauria named

José Bonaparte and Rodolfo Coria in
1993 The United Nations General Assembly, General Assembly of the United Nations designated 1993 as: * International Year for the World's Indigenous People The year 1993 in the Kwajalein Atoll in the Marshall Islands had only 364 days, since its ...
concluded that a new clade of derived sauropods was necessary because ''
Argentinosaurus ''Argentinosaurus'' (meaning "lizard from Argentina") is a genus of giant sauropod dinosaur that lived during the Late Cretaceous Period (geology), period in what is now Argentina. Although it is only known from fragmentary remains, ''Argentinos ...
'', ''Andesaurus'' and ''Epachthosaurus'' were distinct from Titanosauridae as they possessed , but were still very closely related to the titanosaurids. The taxa that possessed the articulations were united within the new family Andesauridae, and the two families were grouped together within the new clade Titanosauria. The titanosaurs were diagnosed by possessing small centered within an anteroposteriorly elongate depression and the presence of two well defined depressions on the posterior face of the neural arch. The entire group was compared favourably with cetiosaurids like ''
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 ...
'' and ''
Volkheimeria ''Volkheimeria'' is an extinct genus of sauropod dinosaurs that lived in what is now Argentina during the Early Jurassic, 178–179 million years ago. Its type and only species is ''Volkheimeria chubutensis''. Discovery and naming The only k ...
''. Overlooking the naming of Titanosauria,
Paul Upchurch Paul may refer to: People * Paul (given name), a given name, including a list of people * Paul (surname), a list of people * Paul the Apostle, an apostle who wrote many of the books of the New Testament * Ray Hildebrand, half of the singing duo ...
in
1995 1995 was designated as: * United Nations Year for Tolerance * World Year of Peoples' Commemoration of the Victims of the Second World War This was the first year that the Internet was entirely privatized, with the United States government ...
named the clade Titanosauroidea, to include ''
Opisthocoelicaudia ''Opisthocoelicaudia'' is a genus of sauropod dinosaur of the Late Cretaceous Period discovered in the Gobi Desert of Mongolia. The type species is ''Opisthocoelicaudia skarzynskii''. A well-preserved skeleton lacking only the head and neck wa ...
'' and the more derived Titanosauridae (''
Malawisaurus ''Malawisaurus'' (meaning "Malawi lizard") is an extinct genus of titanosaurian sauropod dinosaur. It is known from the Dinosaur Beds of northern Malawi, which probably date to the Aptian stage of the Early Cretaceous. The type species is ''M. di ...
'', ''
Alamosaurus ''Alamosaurus'' (; meaning "Ojo Alamo lizard") is a genus of titanosaurian sauropod dinosaurs containing a single known species, ''Alamosaurus sanjuanensis'', from the Maastrichtian age of the Late Cretaceous period in what is now southwestern ...
'' and ''
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 ...
''). United by: caudals with anteriorly-shifted neural spines, extremely robust forearm bones, a prominent concavity on the
ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...
for articulation with the humerus, a laterally flared and flattened ilium, and a less robust pubis; Upchurch considered the clade sister taxon to
Diplodocoidea 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, ...
, because of their shared dental anatomy, although he noted that peg-like teeth might have been independently evolved. This was followed up by Upchurch's
1998 1998 was designated as the ''International Year of the Ocean''. Events January * January 6 – The ''Lunar Prospector'' spacecraft is launched into orbit around the Moon, and later finds evidence for Lunar water, frozen water, in soil i ...
study on sauropod phylogenetics, which additionally recovered ''
Phuwiangosaurus ''Phuwiangosaurus'' (meaning "Phu Wiang lizard") is a genus of titanosaur dinosaur from the Early Cretaceous (Valanginian-Hauterivian) Sao Khua Formation of Thailand. The type species, ''P. sirindhornae'', was described by Martin, Buffetaut, and ...
'' and ''Andesaurus'' within Titanosauroidea and resolved ''Opisthocoelicaudia'' as the sister of ''Saltasaurus'' instead of the most basal titanosauroid. This result places Titanosauroidea in a group with ''
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 ''
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 ...
'', although
Nemegtosauridae Nemegtosauridae is a family of titanosaurian sauropod dinosaurs based on their diplodocid-like skulls. Only three species are known: '' Nemegtosaurus'', '' Quaesitosaurus'' and possibly '' Tapuiasaurus'', each from the Cretaceous. History of cla ...
(''
Nemegtosaurus ''Nemegtosaurus'' (meaning 'Reptile from the Nemegt') was a sauropod dinosaur from the Late Cretaceous Period of what is now Mongolia. Measuring an estimated long and weighing , it was named after the Nemegt Basin in the Gobi Desert, where the ...
'' and ''
Quaesitosaurus ''Quaesitosaurus'' (meaning "extraordinary lizard") is a genus of nemegtosaurid sauropod containing only the type species, ''Q. orientalis'', described in 1983. It lived from 72 to 71 million years ago during the Late Cretaceous epoch in the Barun ...
'') was still classified as the basalmost family of diplodocoids. Upchurch chose to use Titanosauroidea as a replacement name for Titanosauria due to the recommended use of Linnean taxonomy and ranks. In
1997 Events January * January 1 – The Emergency Alert System is introduced in the United States. * January 11 – Turkey threatens Cyprus on account of a deal to buy Russian S-300 missiles, prompting the Cypriot Missile Crisis. * January 1 ...
, Leonardo Salgado ''et al.'' published a phylogenetic study on
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 ...
, including relationships within Titanosauria. They provided a definition for the clade of "including the most recent common ancestor of ''Andesaurus delgadoi'' and Titanosauridae and all of its descendants". Titanosauria resolved including the same two subclades as Bonaparte & Coria (1993), where Andesauridae was monotypic, only including the name genus, and Titanosauridae was all other titanosaurs. Titanosauria was additionally rediagnosed, with eye-shaped pleurocoels, forked infradiapophyseal , centro-parapophyseal laminae, procoelous anterior caudals, and a significantly longer pubis than
ischium The ischium (; : is ...
. Titanosauridae was less strongly defined because of the polytomy between ''Malawisaurus'' and ''Epachthosaurus'', so some diagnostic features couldn't be resolved. Saltasaurinae was defined as the most recent ancestor of ''Neuquensaurus'', ''Saltasaurus'' and its descendants, and diagnosed by short cervical , vertically compressed anterior caudals, and a posteriorly shifted anterior caudal neural spine. Contributing additional work to the systematics of titanosaurs, Spanish paleontologist José Sanz ''et al.'' published an additional study in
1999 1999 was designated as the International Year of Older Persons. Events January * January 1 – The euro currency is established and the European Central Bank assumes its full powers. * January 3 – The Mars Polar Lander is launc ...
, utilizing both the names Titanosauria and Titanosauroidea in displaying their results. Similar to Upchurch (1995), Sanz ''et al.'' recovered ''Opisthocoelicaudia'' as a titanosauroid outside Titanosauria, while Titanosauria was redefined to include only the taxa classified by their study.
Eutitanosauria Eutitanosauria is a clade of titanosaurs, encompassing the more derived members of the group and characterized by the absence of the hyposphene-hypantrum articulation and possibly the presence of osteoderms. The group was first named by Sanz and ...
was proposed as a name for the titanosaurs more derived than ''Epachthosaurus'', and noted the presence of
osteoderms Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of Extant taxon, extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, Temnospondyli, ...
as a probable
synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel Phenotypic trait, character or character state that has evolution, evolved from its ancestral form (or Plesiomorphy and symplesiomorphy, plesiomorphy). A synapomorphy is an apomorphy sh ...
of this clade. ''Aeolosaurus'', ''Alamosaurus'', ''
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. Its remains were found in a level dating from ...
'' and ''
Magyarosaurus ''Magyarosaurus'' (" Hungarian 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 less than long and weighing less than ...
'' were looked at using their character list, but were considered too incomplete to add to the final study. Argentinian paleontologist Jaime Powell published his 1986 thesis in
2003 2003 was designated by the United Nations as the International Year of Fresh water, Freshwater. In 2003, a Multi-National Force – Iraq, United States-led coalition 2003 invasion of Iraq, invaded Iraq, starting the Iraq War. Demographic ...
, with revisions to bring his old work up to date, including the addition of more phylogenetics and the recognition of Titanosauria as a clade name. Using the datamatrix of Sanz ''et al.'' (1999) and modifying it to include additional taxa and some character changes, Powell found that titanosaurs formed mostly a single gradual radiation beginning with ''Epachthosaurus'' as the most basal titanosaur, 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. Its remains were found in a level dating from ...
'' and ''
Isisaurus ''Isisaurus'' (named after the Indian Statistical Institute) is a genus of titanosaurian dinosaur from the Late Cretaceous Lameta Formation of India and Pab Formation of Pakistan. The genus contains a single species, ''Isisaurus colberti''. Di ...
'' as the most derived. Titanosauroidea (following Upchurch 1995), was distinguished by pre- and post-spinal laminae in anterior caudals, a laterally flared ilium, a lateral expansion of the upper femur, and strongly opisthocoelous posterior dorsals. Less inclusive, Titanosauria was diagnosed by horizontally facing dorsal , prominent procoelous anterior caudals, and a ridge on the
sternal plates The sternum (: sternums or sterna) or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood ve ...
. Within Titanosauria, Eutitanosauria was characterized by the absence of a hyposphene-hypantrum, no femoral fourth trochanter, and osteoderms. A small clade of ''Alamosaurus'', ''
Lirainosaurus ''Lirainosaurus'' (meaning "slender lizard"; from the Basque ''lirain'', meaning "slender", and the Greek ''sauros'', meaning "lizard") is a genus of titanosaur sauropod which lived in what is now Spain. The type species, ''Lirainosaurus astibiae ...
'' and the "Peirópolis titanosaur" ('' Trigonosaurus'') was resolved, and diagnosed by only a rotation of the tibia so the proximal end is perpendicular to the distal end. More derived clades, while resolved, were only weakly supported, or characterized by reversions of diagnostic traits of larger groups (below and left). Powell (2003) Curry-Rogers & Forster (2001) ''
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 ...
'' was described in
2001 The year's most prominent event was the September 11 attacks against the United States by al-Qaeda, which Casualties of the September 11 attacks, killed 2,977 people and instigated the global war on terror. The United States led a Participan ...
by Kristina Curry-Rogers and
Catherine Forster Catherine Ann Forster is an American paleontologist, taxonomist and expert in ornithopod evolution and ''Triceratops'' taxonomy. She is a Professor in the Geological Sciences Program and the Department of Biological Sciences at George Washington ...
, who additionally provided a new phylogenetic analysis of
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 ...
(above and right). Titanosauria was strongly supported, distinguished by up to 20 characters depending on unknown traits in basal taxa. Similarly, Saltasaurinae was characterised by up to 16 traits, and the clade of ''Rapetosaurus'' and related taxa possessed four unique features. ''Nemegtosaurus'' and ''Quaesitosaurus'' were resolved within Titanosauria for the first time, after being placed in Diplodocoidea by multiple other analyses, because ''Rapetosaurus'' provided the first significant titanosaur cranial material with associated postcrania. All three genera were resolved in a clade together, although Curry-Rogers & Forster noted that it was possible the group was only resolved because no other titanosaurs had comparable cranial material. ''Opisthocoelicaudia'' was also nested deeply in Saltasaurinae, though a further investigation of titanosaur interrelationships was proposed. American paleontologist Jeff Wilson presented another revision of overall sauropod phylogeny in
2002 The effects of the September 11 attacks of the previous year had a significant impact on the affairs of 2002. The war on terror was a major political focus. Without settled international law, several nations engaged in anti-terror operation ...
, resolving strong support for most groups, and a similar result to Upchurch (1998) although with ''
Euhelopus ''Euhelopus'' is a genus of sauropod dinosaur that lived between 145 and 133 million years ago during the Berriasian and Valanginian ages of the Early Cretaceous in what is now Shandong Province in China. It was a large quadrupedal herbivore. Lik ...
'' closest to titanosaurs instead of outside
Neosauropoda Neosauropoda is a clade within Dinosauria, coined in 1986 by Argentina, Argentine paleontologist José Bonaparte and currently described as ''Saltasaurus loricatus'', ''Diplodocus longus'', and all animals directly descended from their most recent ...
. More internal clades were resolved for Titanosauria, with ''Nemegtosaurus'' and ''Rapetosaurus'' united within Nemegtosauridae, and
Saltasauridae Saltasauridae (named after the Salta region of Argentina where they were first found) is a family of armored herbivorous sauropods from the Upper Cretaceous. They are known from fossils found in South America, Africa, Asia, North America, and Eur ...
including two subfamilies, Opisthocoelicaudiinae and Saltasaurinae. Saltasauridae was defined as a node-stem triplet, where everything descended from the common ancestor of ''Opisthocoelicaudia'' and ''Saltasaurus'' was within Saltasauridae, and the subfamilies Saltasaurinae and Opisthocoelicaudiinae were for every taxon on one branch of the saltasaurid tree or the other. Wilson and Paul Upchurch followed this study up in
2003 2003 was designated by the United Nations as the International Year of Fresh water, Freshwater. In 2003, a Multi-National Force – Iraq, United States-led coalition 2003 invasion of Iraq, invaded Iraq, starting the Iraq War. Demographic ...
with a significant revision of the type genus ''Titanosaurus'', and revisited all the material that had been assigned to the genus while reviewing titanosaur inter-relationships. Because they found ''Titanosaurus'' to be a
dubious name In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium,'' it may be impossible to determine whether a ...
, they proposed that Linnaean-named groups Titanosauridae and Titanosauroidea should be considered invalid as well. Wilson & Upchurch (2003) supported the definition of Salgado ''et al.'' (1997) for Titanosauria, since it was oldest and most similar to the original content of the group when named by Bonaparte & Coria (1993).
Lithostrotia Lithostrotia is a clade of derived titanosaur sauropods that lived during the Early Cretaceous and Late Cretaceous. The group was defined by Upchurch ''et al.'' in 2004 as the most recent common ancestor of ''Malawisaurus'' and ''Saltasaurus'' an ...
(Upchurch ''et al.'' 2004) was defined to be ''
Malawisaurus ''Malawisaurus'' (meaning "Malawi lizard") is an extinct genus of titanosaurian sauropod dinosaur. It is known from the Dinosaur Beds of northern Malawi, which probably date to the Aptian stage of the Early Cretaceous. The type species is ''M. di ...
'' and all more derived titanosaurs, and the clade
Eutitanosauria Eutitanosauria is a clade of titanosaurs, encompassing the more derived members of the group and characterized by the absence of the hyposphene-hypantrum articulation and possibly the presence of osteoderms. The group was first named by Sanz and ...
(Sanz ''et al.'' 1999) was considered a possible synonym of
Saltasauridae Saltasauridae (named after the Salta region of Argentina where they were first found) is a family of armored herbivorous sauropods from the Upper Cretaceous. They are known from fossils found in South America, Africa, Asia, North America, and Eur ...
. Wilson & Upchurch (2003) presented a reduced cladogram of Titanosauria, including only the most commonly-analyzed taxa from previous studies, resulting in a tree similar to that of Wilson (2002) but with ''Rapetosaurus'' and ''Nemegtosaurus'' excluded and ''Epachthosaurus'' included. ''Alamosaurus'' and ''Opisthocoelicaudia'' were united within Opisthocoelicaudiinae, ''Neuquensaurus'' and ''Saltasaurus'' formed Saltasaurinae, and ''Isisaurus'' placed as the next most derived titanosaurid. At the same time as Wilson & Upchurch redescribing the species of ''Titanosaurus'', Saldago (2003) looked over the potential invalidity of the family Titanosauridae and redefined the internal clades of Titanosauria. Titanosauria was defined as more inclusive than Titanosauroidea, contrasting with earlier used by Upchurch (1995) and Sanz ''et al.'' (1999), as all taxa in
Somphospondyli Somphospondyli is an extinct clade of titanosauriformes, titanosauriform sauropods that lived from the Late Jurassic until the end of the Late Cretaceous, comprising all titanosauriforms more closely related to Titanosauria proper than Brachiosau ...
closer to ''Saltasaurus'' than ''
Euhelopus ''Euhelopus'' is a genus of sauropod dinosaur that lived between 145 and 133 million years ago during the Berriasian and Valanginian ages of the Early Cretaceous in what is now Shandong Province in China. It was a large quadrupedal herbivore. Lik ...
''. In order to create additional stability, Saldago also defined
Andesauroidea ''Andesaurus'' ( ; "Andes lizard") is a genus of Basal (phylogenetics), basal titanosaurian sauropod dinosaur which existed during the middle of the Cretaceous Period in South America. Like most sauropods, it would have had a small head on the en ...
for only ''Andesaurus'', as every titanosaur closer to that genus than ''Saltasaurus'', and also it's opposite Titanosauroidea as every titanosaur closer to ''Saltasaurus'' than ''Andesaurus''. Next most inclusive, Salgado revitalised Titanosauridae to include everything descended from the ancestor of ''Epachthosaurus'' and ''Saltasaurus'', and to replace the node-stem triplet of Saltasauridae, defined the clades Epachthosaurinae and Eutitanosauria as ''Epachthosaurus''>''Saltasaurus'' and ''Saltasaurus''<''Epachthosaurus'' respectively. Saltasaurinae and Opisthocoelicaudiinae were retained with their original definitions, but Lithostrotia was considered a synonym of Titanosauridae, and Titanosaurinae was considered a
paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
clade of unrelated titanosaurids. Following the clade definitions proposed in previous Salgado studies, Bernardo González-Riga published two papers in 2003 describing new taxa in Titanosauria: '' Mendozasaurus'', and ''
Rinconsaurus ''Rinconsaurus'' is a genus of titanosaur sauropod dinosaur from the Late Cretaceous in what is now Argentina. The type species, ''Rinconsaurus caudamirus'', was described by Calvo and Riga in 2003, and is based on three partial skeletons. Desc ...
'' (with
Jorge O. Calvo Jorge Orlando Calvo (27 April 1961 – 10 January 2023) For ''Mendozasaurus'', the new genus grouped with ''Malawisaurus'' as basal within Titanosauridae, but because of the features of caudal vertebrae in these basal taxa, González-Riga recommended revising the diagnosis of the family, instead of changing the content. The situation of caudals in ''Rinconsaurus'' also suggested procoelous caudals were no longer diagnostic, because in the tail of ''Rinconsaurus'' the vertebrae regularly changed their articular surfaces, being from procoelous caudals interspersed with amphicoelous, opisthocoelous and biconvex vertebrae. ''Rinconsaurus'' was then included in
Aeolosaurini Aeolosaurini is an extinct clade of titanosaurian dinosaurs known from the Cretaceous period of Argentina and Brazil. Rodrigo M. Santucci and Antonio C. de Arruda-Campos (2011) in their cladistic analysis found ''Aeolosaurus'', '' Gondwanatitan'' ...
, a clade named the following year by Aldirene Franco-Rosas ''et al.'' containing everything closer to ''Aeolosaurus'' and ''Gondwanatitan'' than ''Saltasaurus'' or ''Opisthocoelicaudia''. Only the three genera and various intermediate specimens were included in Aeolosaurini in their
2004 2004 was designated as an International Year of Rice by the United Nations, and the International Year to Commemorate the Struggle Against Slavery and Its Abolition (by UNESCO). Events January * January 3 – Flash Airlines Flight 60 ...
paper, with the tribe being considered to be within Saltasaurinae. The second edition of ''
The Dinosauria ''The Dinosauria'' is an encyclopedia on dinosaurs, edited by paleontologists David B. Weishampel, Peter Dodson, and Halszka Osmólska. It has been published in two editions by the University of California Press, with the first edition in 1990 ...
'', published in
2004 2004 was designated as an International Year of Rice by the United Nations, and the International Year to Commemorate the Struggle Against Slavery and Its Abolition (by UNESCO). Events January * January 3 – Flash Airlines Flight 60 ...
, included newly described titanosaurs and other taxa reidentified as titanosaurs. Written by Upchurch,
Paul Barrett Paul Franklyn "Legs" Barrett (14 December 1940 – 20 January 2019) was a UK agent and manager of 1950s style rock and roll artists, an author and previously a singer, songwriter and film actor. Barrett was the discoverer, mentor and first man ...
and
Peter Dodson Peter Dodson (born August 20, 1946) is an American paleontologist who has published many papers and written and collaborated on books about dinosaurs. An authority on Ceratopsians, he has also authored several papers and textbooks on hadrosaurs a ...
, a review of Sauropoda included a more expansive Titanosauria for sauropods more derived than brachiosaurids. Titanosauria, defined as everything closer to ''Saltasaurus'' than ''
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 ...
'', included a very large variety of taxa, and the new clade
Lithostrotia Lithostrotia is a clade of derived titanosaur sauropods that lived during the Early Cretaceous and Late Cretaceous. The group was defined by Upchurch ''et al.'' in 2004 as the most recent common ancestor of ''Malawisaurus'' and ''Saltasaurus'' an ...
was named for a large number of more derived taxa, although Nemegtosauridae was placed in Diplodocoidea following earlier publications of Upchurch. Lithostrotia adopted the distinguishing feature of strongly procoelous caudals, previously used for Titanosauria.


New phylogenetic frameworks

In
2005 2005 was designated as the International Year for Sport and Physical Education and the International Year of Microcredit. The beginning of 2005 also marked the end of the International Decade of the World's Indigenous Peoples, Internationa ...
, Curry-Rogers proposed a new phylogenetic analysis that focused on the inter-relationships of Titanosauria and included the most expansive character and taxon list of any study before it. 364 characters were selected from all previous phylogenetic analyses and scored across 29 probable titanosaurs, ranging from 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 ...
African ''Janenschia'' to the large variety of Late Cretaceous global genera. Proposing her analysis as the basis for a new phylogenetic framework of Titanosauria, Curry-Rogers recommended only using named for clades that were very strongly supported. For the strict consensus, every taxon more derived than ''Brachiosaurus'' was in an unresolved polytomy except for a clade of ''Rapetosaurus'' and ''Nemegtosaurus'', and one of Saltasaurinae. Within the recommended results, she only named Titanosauria, Lithostrotia, Saltasauridae, Saltasaurinae and Opisthocoelicaudiinae, because of the weakness of support (below and left). Curry-Rogers (2005) Carballido ''et al.'' (2017) Another form of composite matrix was created by Calvo, González-Riga and Juan Porfiri in
2007 2007 was designated as the International Heliophysical Year and the International Polar Year. Events January * January 1 **Bulgaria and Romania 2007 enlargement of the European Union, join the European Union, while Slovenia joins the Eur ...
, based upon multiple previous studies between 1997 and 2003. The final analysis included 15 titanosaurs and 65 characters, and the typical titanosaur subclades were resolved, Titanosauridae being used over Lithostrotia following Salgado (2003), and the new clade
Rinconsauria Rinconsauria is an extinct clade of titanosaurian sauropods known from the late Cretaceous period of Argentina. All members of this clade are fairly small compared to the largest titanosaurs, at less than around long. The membership of Rinconsau ...
for the clade of ''
Rinconsaurus ''Rinconsaurus'' is a genus of titanosaur sauropod dinosaur from the Late Cretaceous in what is now Argentina. The type species, ''Rinconsaurus caudamirus'', was described by Calvo and Riga in 2003, and is based on three partial skeletons. Desc ...
'' and '' Muyelensaurus''. The new clade (defined as ''Rinconsaurus'' and ''Muyelensaurus'') was placed as the sister taxon of Aeolosaurini, which together grouped with ''Rapetosaurus'' as sister to Saltasauridae. In the same year, Calvo ''et al.'' published another paper, describing the basal titanosaur ''
Futalognkosaurus ''Futalognkosaurus'' ( ; meaning "giant chief lizard") is a genus of titanosaurian dinosaur. The herbivorous ''Futalognkosaurus'' lived approximately 87 million years ago in the Portezuelo Formation, in what is now Argentina, of the Coniacian st ...
''. The only difference in the resulting phylogeny, based on the matrix of the Calvo, González-Riga & Porfiri (2007), was the addition of ''Futalognkosaurus'' as the sister taxon to '' Mendozasaurus'' in a clade Calvo ''et al.'' named Lognkosauria, defined by the two genera classified within it. A very similar result was also recovered by González-Riga ''et al.'' in
2009 2009 was designated as the International Year of Astronomy by the United Nations to coincide with the 400th anniversary of Galileo Galilei's first known astronomical studies with a telescope and the publication of Astronomia Nova by Joha ...
in a phylogenetic analysis based partially on that of Calvo ''et al.'' (2007), although ''Epachthosaurus'' was nested with ''Rapetosaurus'' outside the clades of aeolosaurines. Further updates and modifications were then made by Palbo Gallina & Apesteguía in
2011 The year marked the start of a Arab Spring, series of protests and revolutions throughout the Arab world advocating for democracy, reform, and economic recovery, later leading to the depositions of world leaders in Tunisia, Egypt, and Yemen ...
, with the additions of ''
Ligabuesaurus ''Ligabuesaurus'' is a genus of titanosauriformes, somphospondylan sauropod from the Early Cretaceous Lohan Cura Formation of what is now Argentina. The type species, ''Ligabuesaurus leanzai'', was described in 2006, based on a partial skeleton wi ...
'', ''Antarctosaurus'', ''Nemegtosaurus'' and ''
Bonitasaura ''Bonitasaura'' is a genus of titanosaurian dinosaur hailing from uppermost layers of the Late Cretaceous (Santonian) Bajo de la Carpa Formation, Neuquén Group of the eastern Neuquén Basin, located in Río Negro Province, Northwestern Patagonia ...
'' and character updates to match, bringing the total to 77 characters and 22 taxa. Significantly contrasting the earlier results, internal relationships of Titanosauria were rearranged. ''Malawisaurus'' nested with ''Andesaurus'' in a clade of the basalmost titanosaurs outside Titanosauroidea, where ''Lirainosaurus'', instead of being the basal member of the saltasaur-branch was instead basalmost titanosauroid. Lognkosauria moved to be within rinconsaurs, while Nemegtosauridae was resolved as the sister of ''Aeolosaurus'' and ''Gondwanatitan'', and the rinconsaur-lognkosaur branch. ''Antarctosaurus'' was unstable, but placed in a polytomy with the lognkosaurs and rinconsaurs before being excluded. Saltasaurinae and its relationship with ''Opisthocoelicaudia'' remained the same. Nemegtosauridae was additionally revised by Hussam Zaher ''et al.'' (2011) with the description of ''
Tapuiasaurus ''Tapuiasaurus'' (meaning " Tapuia lizard") is a genus of titanosaur which lived during the Lower Cretaceous period (Aptian age) in what is now Minas Gerais, Brazil. Discovery Its fossils, including a partial skeleton with a nearly complet ...
'', which nested closer to ''Rapetosaurus'' than ''Nemegtosaurus'', with all three forming a clade of derived lithostrotians. Using the matrix of Wilson (2002), following the additions of a few cranial characters and '' Diamantinasaurus'', ''
Tangvayosaurus ''Tangvayosaurus'' (meaning "Tang Vay lizard") is a genus of sauropod dinosaur from the Aptian-Albian age Lower Cretaceous Gres superieurs Formation of Savannakhet Province, Laos. It was a basal somphospondylan, about 15 m long, and is kno ...
'' and ''
Phuwiangosaurus ''Phuwiangosaurus'' (meaning "Phu Wiang lizard") is a genus of titanosaur dinosaur from the Early Cretaceous (Valanginian-Hauterivian) Sao Khua Formation of Thailand. The type species, ''P. sirindhornae'', was described by Martin, Buffetaut, and ...
'', remained the same as originally found by Wilson but with ''Diamantinasaurus'' sister to Saltasauridae and the other two genera as basal titanosaurs outside Lithostrotia, since Titanosauria, while undefined, was labelled to include all taxa closer to ''Saltasaurus'' than ''
Euhelopus ''Euhelopus'' is a genus of sauropod dinosaur that lived between 145 and 133 million years ago during the Berriasian and Valanginian ages of the Early Cretaceous in what is now Shandong Province in China. It was a large quadrupedal herbivore. Lik ...
''. Following a revision of the skull of ''Tapuiasaurus'', Wilson ''et al.'' (
2016 2016 was designated as: * International Year of Pulses by the sixty-eighth session of the United Nations General Assembly. * International Year of Global Understanding (IYGU) by the International Council for Science (ICSU), the Internationa ...
) rescored the analysis of Zaher ''et al.'' and recovered similar results for everything but Nemegtosauridae, where the family dissolved into a more basal ''Tapuiasaurus'' outside Lithostrota and ''Nemegtosaurus'' outside Saltasauridae. While non-titanosaur phylogeny remained identical in every single result, the topology within Titanosauria was very labile and prone to change with minor adjustments. Also following the 2002 analysis of Wilson, José Carballido and colleagues published a redescription of ''
Chubutisaurus ''Chubutisaurus'' (meaning "Chubut lizard") is a genus of somphospondylan sauropod dinosaur from the Early Cretaceous Cerro Barcino Formation (Albian) of Argentina. The type species, ''Chubutisaurus insignis'', was described by del Corro in 197 ...
'' in 2011, and utilized an updated Wilson matrix, expanded to 289 characters across 41 taxa, including 15 titanosaurs. The primary focus of the analysis was on the basal titanosauriform taxa, but Titanosauria was defined, as the most recent common ancestor of ''Andesaurus delgadoi'' and ''Saltasaurus loricatus'', and all its descendants, although the only autapomorphy of the group recovered was the absence of a prominent ventral process on the scapula. This same matrix and basis of characters was further utilized and expanded for analyses on '' Tehuelchesaurus'', ''
Comahuesaurus ''Comahuesaurus'' (meaning "Comahue lizard", after the region in which it was found) is a genus of sauropod dinosaur of the family Rebbachisauridae. It was found in the Lohan Cura Formation, in Argentina and lived during the Early Cretaceous, Ap ...
'' and related rebbachisaurs, ''
Europasaurus ''Europasaurus'' (meaning 'Europe lizard') is a basal macronarian sauropod, a form of quadrupedal herbivorous dinosaur. It lived during the Late Jurassic (middle Kimmeridgian, from about 154 to 151 million years ago) of northern Germany, and has ...
'', and ''
Padillasaurus ''Padillasaurus'' is an extinct genus of titanosauriform sauropod known from the Early Cretaceous (Barremian stage) Paja Formation in Colombia. It contains a single species, ''Padillasaurus leivaensis'', known only from a single partial axial sk ...
'', before being expanded upon once again in
2017 2017 was designated as the International Year of Sustainable Tourism for Development by the United Nations General Assembly. Events January * January 1 – Istanbul nightclub shooting: A gunman dressed as Santa Claus opens fire at the ...
by Carballido ''et al.'' during the description of ''
Patagotitan ''Patagotitan'' is a genus of titanosaurian sauropoda, sauropod dinosaur from the Cerro Barcino Formation in Chubut Province, Patagonia, Argentina. The genus contains a single species known from at least six young adult individuals, ''Patagotita ...
'' to 405 characters and 87 taxa, including 28 titanosaurs (above and right). The definition of Titanosauria was preserved following Salgado ''et al.'' (1997) as ''Andesaurus'' plus ''Saltasaurus''. Eutitanosauria (closer to ''Saltasaurus'' than ''Epachthosaurus'') was resolved as a very inclusive clade composed of two distinct branches, one leading to the larger-bodied lognkosaurs and the other to the smaller-bodied saltasaurs. On the lognkosaur branch of Eutitanosauria, there is a branch of lognkosaurs and one of Rinconsauria. Following Calvo, González-Riga and Porfiri (2007), Rinconsauria was defined as ''Muyelensaurus'' plus ''Rinconsaurus'', and Lognkosauria was defined as ''Mendozasaurus'' plus ''Futalognkosaurus''. Rinconsauria included taxa typically found within Aeolosaurini as well, so Aeolosaurini was redefined as ''Aeolosaurus rionegrinus'' plus ''Gondwanatitan'' to preserve the original restricted content, otherwise the entire rinconsaur-lognkosaur branch would be classified within Aeolosaurini. Lithostrotia, Saltasauridae and Saltasaurinae had their definitions preserved from earlier studies, and included their typical content. Philip Mannion and colleagues redescribed ''
Lusotitan ''Lusotitan'' is a genus of herbivorous brachiosaurid sauropod dinosaur from the Late Jurassic of Portugal and possibly Spain. Discovery and naming In 1947 Manuel de Matos, a member of the Geological Survey of Portugal, discovered large saur ...
'' in
2013 2013 was the first year since 1987 to contain four unique digits (a span of 26 years). 2013 was designated as: *International Year of Water Cooperation *International Year of Quinoa Events January * January 5 – 2013 Craig, Alask ...
, creating a new analysis of 279 characters drawn from significant previous analyses by Upchurch and Wilson supplemented by other studies. 63 sauropods were included, focusing on non-titanosaurian sauropods, although 14 probable titanosaurs were included. Unique to Mannion ''et al.'', continuous characters were distinguished in a run of the matrix, which resolved almost all of
Somphospondyli Somphospondyli is an extinct clade of titanosauriformes, titanosauriform sauropods that lived from the Late Jurassic until the end of the Late Cretaceous, comprising all titanosauriforms more closely related to Titanosauria proper than Brachiosau ...
within Titanosauria because of ''Andesaurus'' placing very basal in a large group of Andesauroidea. Titanosauroidea was tentatively retained as the opposite clade of titanosaurs, which included all other traditional titanosaurs, although it was noted because of the invalidity of ''Titanosaurus'', Titanosauroidea should be considered an invalid name as well. While the original analysis didn't focus on titanosaurs, it was utilised during the descriptions of ''
Savannasaurus ''Savannasaurus'' is a genus of titanosaurian sauropoda, sauropod dinosaur from the Late Cretaceous Winton Formation of Queensland, Australia. It contains one species, ''Savannasaurus elliottorum'', named in 2016 by Stephen Poropat and colleagues ...
'' and '' Diamantinasaurus'', ''
Yongjinglong ''Yongjinglong'' is an extinct genus of titanosauriform sauropod dinosaur known from the Early Cretaceous of Lanzhou-Minhe Basin of Gansu Province, China. It contains a single species, ''Yongjinglong datangi''. Discovery ''Yongjinglong'' was f ...
'', an osteology of ''Mendozasaurus'', and redescribing ''
Tendaguria ''Tendaguria'' ( ; meaning "the Tendaguru one") is a genus of herbivorous sauropod dinosaur from the Late Jurassic of Lindi Region, Tanzania. Discovery and naming In 1911, German geologist Wilhelm Bornhardt at Nambango in German East Africa disc ...
''. From these updates, an analysis of 548 characters and 124 taxa was published by Mannion ''et al.'' in
2019 This was the year in which the first known human case of COVID-19 was documented, preceding COVID-19 pandemic, the pandemic which was declared by the World Health Organization the following year. Up to that point, 2019 had been described as ...
for a redescription of '' Jiangshanosaurus'' and ''
Dongyangosaurus ''Dongyangosaurus'' is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous. The only species is ''Dongyangosaurus sinensis'', from which only a single fragmentary skeleton is known, coming from the Zhejiang province of eastern Chin ...
'', and additional revisions of ''
Ruyangosaurus ''Ruyangosaurus'' (Ruyang County lizard) is a genus of macronaria, titanosauriform sauropod dinosaur recovered from the Early Cretaceous Haoling Formation of China. The type species is ''R. giganteus'', described in 2009 in paleontology, 2009 by ...
'' were made. No differentiation between continuous and discrete characters was made like performed by Mannion ''et al.'' (2013), but a large clade of Andesauroidea was still resolved with implied weights. Both redescribed Asian taxa, as well as ''Yongjinglong'', previously considered derived titanosaurs related to Saltasauridae, were removed to outside the clade. In the description of ''
Mansourasaurus ''Mansourasaurus'' ("Mansoura lizard") is a genus of herbivorous lithostrotian sauropod dinosaur from the Quseir Formation of Egypt. The type and only species is ''Mansourasaurus shahinae''. The discovery of ''Mansourasaurus'' was considered q ...
'', Sallam ''et al.'' (2017) published a phylogenetic analysis of Titanosauria including the most taxa of any analysis of the clade. In an updated version of the analysis, with the taxon ''
Mnyamawamtuka ''Mnyamawamtuka'' (; meaning "beast of the Mtuka river drainage" in Kiswahili) is a genus of lithostrotian titanosaur sauropod dinosaur from the Cretaceous Galula Formation in Tanzania. The type and only species is ''M. moyowamkia''. Discovery ...
'' added, Gorscak & O'Connor (2019) got similar results, with slightly different relationships within small clades.


Paleobiology


Diet

Fossilized dung associated with late Cretaceous titanosaurids from India has revealed
phytoliths Phytoliths (from Greek, "plant stone") are rigid, microscopic mineral deposits found in some plant tissues, often persisting after the decay of the plant. Although some use "phytolith" to refer to all mineral secretions by plants, it more commonl ...
, silicified plant fragments, that offer clues to a broad, unselective plant diet. Besides the plant remains that might have been expected, such as
cycad Cycads are seed plants that typically have a stout and woody (ligneous) trunk (botany), trunk with a crown (botany), crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants o ...
s and
conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...
s, discoveries published in 2005 revealed an unexpectedly wide range of
monocotyledon Monocotyledons (), commonly referred to as monocots, ( Lilianae '' sensu'' Chase & Reveal) are flowering plants whose seeds contain only one embryonic leaf, or cotyledon. A monocot taxon has been in use for several decades, but with various ranks ...
s, including
palm Palm most commonly refers to: * Palm of the hand, the central region of the front of the hand * Palm plants, of family Arecaceae ** List of Arecaceae genera **Palm oil * Several other plants known as "palm" Palm or Palms may also refer to: Music ...
s and grasses (
Poaceae Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivate ...
), including ancestors of
rice Rice is a cereal grain and in its Domestication, domesticated form is the staple food of over half of the world's population, particularly in Asia and Africa. Rice is the seed of the grass species ''Oryza sativa'' (Asian rice)—or, much l ...
and
bamboo Bamboos are a diverse group of mostly evergreen perennial plant, perennial flowering plants making up the subfamily (biology), subfamily Bambusoideae of the grass family Poaceae. Giant bamboos are the largest members of the grass family, in th ...
, which has given rise to speculation that herbivorous dinosaurs and grasses co-evolved.


Nesting

A large titanosaurid
nest A nest is a structure built for certain animals to hold Egg (biology), eggs or young. Although nests are most closely associated with birds, members of all classes of vertebrates and some invertebrates construct nests. They may be composed of ...
ing ground was discovered in Auca Mahuevo, in
Patagonia Patagonia () is a geographical region that includes parts of Argentina and Chile at the southern end of South America. The region includes the southern section of the Andes mountain chain with lakes, fjords, temperate rainforests, and glaciers ...
, Argentina and another colony has reportedly been discovered in Spain. Several hundred female saltasaurs dug holes with their back feet, laid eggs in clutches averaging around 25 eggs each, and buried the nests under dirt and vegetation. The small
egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the ...
s, about in
diameter In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions a ...
, contained
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 ...
ised
embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...
s, complete with
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...
impressions. The impressions showed that titanosaurs were covered in a mosaic armour of small bead-like scales. The huge number of individuals gives evidence of
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'' ...
behavior, which, along with their armor, could have helped provide protection against large predators such as ''
Abelisaurus ''Abelisaurus'' (; "Abel's lizard") is a genus of predatory abelisaurid theropod dinosaur alive during the Late Cretaceous Period (geology), Period (Campanian) of what is now South America. It was a bipedal carnivore that probably reached about ...
''.


Range

The titanosaurs were the last great group of sauropods, which existed from about 136 to 66
million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...
, before the
Cretaceous–Paleogene extinction event The Cretaceous–Paleogene (K–Pg) extinction event, also known as the K–T extinction, was the extinction event, mass extinction of three-quarters of the plant and animal species on Earth approximately 66 million years ago. The event cau ...
, and were the dominant
herbivore 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 ...
s of their time. The fossil evidence suggests they replaced the other sauropods, like the
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 the
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 l ...
s, which died out between the late
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 143.1 Mya. ...
and the mid-
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 ...
Periods. Titanosaurs were widespread. In December 2011, Argentine scientists announced titanosaur fossils had been found on Antarctica—meaning that titanosaur fossils have been found on all continents. They are especially numerous in the southern continents (then part of the
supercontinent In geology, a supercontinent is the assembly of most or all of Earth's continent, continental blocks or cratons to form a single large landmass. However, some geologists use a different definition, "a grouping of formerly dispersed continents", ...
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 ...
). Australia had titanosaurs around 96 million years ago: fossils have been discovered in
Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...
of a creature around long. Remains have also been discovered in New Zealand. One of the largest ever titanosaur footprints was discovered in the
Gobi Desert The Gobi Desert (, , ; ) is a large, cold desert and grassland region in North China and southern Mongolia. It is the sixth-largest desert in the world. The name of the desert comes from the Mongolian word ''gobi'', used to refer to all of th ...
in 2016. One of the oldest remains of this group was described by Ghilardi et al. (2016). It was found from the
Valley of the Dinosaurs ''Valley of the Dinosaurs'' is an American animated television series produced by the Australian studios of Hanna-Barbera Productions and broadcast on CBS from September 7 to December 21, 1974, and in syndication from 1977 to 1983. The series, ab ...
,
Paraíba Paraíba ( , ; ) is a states of Brazil, state of Brazil. It is located in the Brazilian Northeast, and it is bordered by Rio Grande do Norte to the north, Ceará to the west, Pernambuco to the south and the Atlantic Ocean to the east. Paraíba i ...
state of
Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
, representing a 136-million-year-old subadult individual.


Paleopathology

''
Ibirania ''Ibirania'' (meaning "Ibirá wanderer" or "tree wanderer") is a genus of dwarf saltasaurine titanosaur dinosaur from the Late Cretaceous (Santonian to Campanian) São José do Rio Preto Formation (Bauru Group, Bauru Basin) of Southeast Brazil. Th ...
'', a nanoid titanosaur fossil from Brazil suggests that individuals of various genera were susceptible to diseases such as
osteomyelitis Osteomyelitis (OM) is the infectious inflammation of bone marrow. Symptoms may include pain in a specific bone with overlying redness, fever, and weakness. The feet, spine, and hips are the most commonly involved bones in adults. The cause is ...
and parasite infestations. The specimen hails from the late cretaceous
São José do Rio Preto Formation SAO or Sao may refer to: Places * Sao civilisation, in Middle Africa from 6th century BC to 16th century AD * Sao, a town in Boussé Department, Burkina Faso * Serb Autonomous Regions (''Srpska autonomna oblast'', SAO), during the breakup of Y ...
,
Bauru Basin The Bauru Group is a geological group of the Bauru Sub-basin, Paraná Basin in Minas Gerais, São Paulo, General Salgado, Itapecuru-Mirim, Mato Grosso, Brazil whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils t ...
, and was described in the journal ''Cretaceous Research'' by Aureliano et al. (2021). Examination of the titanosaur's bones revealed what appear to be parasitic blood worms similar to the prehistoric ''
Paleoleishmania ''Paleoleishmania'' is an extinct genus of kinetoplastids, a monophyletic group of unicellular parasitic flagellate protozoa. At present it is placed in the family Trypanosomatidae. The genus contains two species, the type species ''Paleoleishm ...
'' but are 10-100 times larger, that seemed to have caused the osteomyelitis. The fossil is the first known instance of an aggressive case of osteomyelitis being caused by blood worms in an extinct animal.


References


External links

{{Portal bar, Dinosaurs, Paleontology Dinosaur clades Cretaceous dinosaurs