Antarctosaurus
Encyclopedia
Antarctosaurus is a genus
of titanosaurian sauropod dinosaur
from the Late Cretaceous
Period of what is now South America
. The type species
, A. wichmannianus, was described by prolific German
paleontologist
Friedrich von Huene
in 1929, who also described a second species in 1929. Three additional species of Antarctosaurus have been named since then. Later studies indicate that none of these pertain to Antarctosaurus.
Antarctosaurus was very large, even for a dinosaur. Scientists still have much to learn about Antarctosaurus, as a complete skeleton remains elusive.
al herbivore
with a long neck and tail. It was possibly armoured
. As Antarctosaurus is not known from a complete skeleton and tail lengths are highly variable among sauropods, the true size of these animals is hard to extrapolate. The type species
may have been over 60 feet (18 meters) long, and a second species may have been one of the largest land animals ever. Antarctosaurus may have been as tall as 15 feet at the shoulder.
. Antarctosaurus does not refer to the continent of Antarctica, since it was first found in Argentina
, although it does have the same derivation, from the Greek
words αντι-, anti- meaning 'opposite of', αρκτός, arktos meaning 'north' and σαυρος, sauros meaning 'lizard'. The generic name refers to the animal's reptilian
nature and its geographical location on a southern continent.
have been assigned to Antarctosaurus over the years, probably incorrectly in most cases.
of the genus, named in 1929 after the discoverer of its remains, geologist R. Wichmann.
Von Huene used the name A. wichmannianus to describe a large assemblage of bones, which are now considered to come from the Anacleto Formation
in Río Negro Province
of Argentina
, which is considered to be early Campanian
in age or about 83-80 million years old. Several skull
fragments were described, including a braincase and a mandible
(lower jaw). Other bones referred to this dinosaur include neck and tail vertebrae, rib
s, and numerous limb bones. One femur
(thigh bone) is over 6 feet (1.85 meters) tall, which has been used to extrapolate a mass of about 34 metric tonnes, or nearly 75,000 pounds
.
These bones were for the most part not associated with each other but scattered throughout the formation. Consequently, many scientists believe that they may not all belong to the same type of animal. In particular, the very square lower jaw has frequently been suggested to belong to a rebbachisaurid sauropod similar to Nigersaurus
. However the jaw of Bonitasaura
is similar in overall shape and is clearly associated with titanosaur skeletal remains, indicating that the lower jaw may belong to Antarctosaurus wichmannianus after all. The back of the skull and the remainder of the skeleton are usually regarded as titanosaurian, although they do not necessarily belong to the same type of titanosaur. A. wichmannianus (minus the lower jaw) has been regarded as a lithostrotian, a group which includes armored titanosaurs, although no armor scutes were associated with its remains. This species has also been regarded as a possible nemegtosaurid titanosaur.
by some. The most famous of these bones are two gigantic femora, which are among the largest of any known sauropod. They measure about 7.75 feet (2.35 meters) in length. Extrapolating from the size of these bones has led to a mass estimate of approximately 69 metric tonnes (152,000 pounds) in one study, just a little smaller than the gigantic Argentinosaurus
, which at nearly 73 metric tonnes (160,000 pounds) would have been the heaviest known land animal of all time.
The bones mentioned above were recovered in Neuquén Province
of Argentina, from the Plottier Formation
, which dates to the late Coniacian
stage of the Late Cretaceous
Period, or about 87 to 85 million years ago. The Plottier, like the younger Anacleto, is a member of the Neuquén Group
.
As so little is known of this animal, and because the material assigned to A. wichmannianus is so confused, A. giganteus cannot be confidently assigned to the genus Antarctosaurus at this time.
. This species does preserve important anatomical information but does not belong to Antarctosaurus. It was renamed Jainosaurus
in 1994.
forms the basis of this species, which was named by Soviet paleontologist Anatoly Riabinin in 1939. It is regarded as a nomen dubium today but is almost certainly not a species of the South American Antarctosaurus.
and described by Arid and Vizzotto in 1971. This species is also considered a nomen dubium.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of titanosaurian sauropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from the Late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
Period of what is now South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, A. wichmannianus, was described by prolific German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
paleontologist
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
Friedrich von Huene
Friedrich von Huene
Friedrich von Huene was a German paleontologist who named more dinosaurs in the early 20th century than anyone else in Europe.-Biography:...
in 1929, who also described a second species in 1929. Three additional species of Antarctosaurus have been named since then. Later studies indicate that none of these pertain to Antarctosaurus.
Antarctosaurus was very large, even for a dinosaur. Scientists still have much to learn about Antarctosaurus, as a complete skeleton remains elusive.
Description
Antarctosaurus was a huge quadrupedQuadruped
Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
al herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
with a long neck and tail. It was possibly armoured
Armour (zoology)
Armour in animals is external or superficial protection against attack by predators, formed as part of the body , usually through the hardening of body tissues, outgrowths or secretions. It has therefore mostly developed in 'prey' species...
. As Antarctosaurus is not known from a complete skeleton and tail lengths are highly variable among sauropods, the true size of these animals is hard to extrapolate. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
may have been over 60 feet (18 meters) long, and a second species may have been one of the largest land animals ever. Antarctosaurus may have been as tall as 15 feet at the shoulder.
Etymology
Remains of this dinosaur were first mentioned in print in 1916, although they were not fully described and named until a 1929 manuscript written by paleontologist Friedrich von HueneFriedrich von Huene
Friedrich von Huene was a German paleontologist who named more dinosaurs in the early 20th century than anyone else in Europe.-Biography:...
. Antarctosaurus does not refer to the continent of Antarctica, since it was first found in Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
, although it does have the same derivation, from the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
words αντι-, anti- meaning 'opposite of', αρκτός, arktos meaning 'north' and σαυρος, sauros meaning 'lizard'. The generic name refers to the animal's reptilian
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
nature and its geographical location on a southern continent.
Species of Antarctosaurus
Several speciesSpecies
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
have been assigned to Antarctosaurus over the years, probably incorrectly in most cases.
Antarctosaurus wichmannianus
This is the type speciesType species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
of the genus, named in 1929 after the discoverer of its remains, geologist R. Wichmann.
Von Huene used the name A. wichmannianus to describe a large assemblage of bones, which are now considered to come from the Anacleto Formation
Anacleto Formation
The Anacleto Formation is a geologic formation with outcroppings in the Argentine Patagonian provinces of Mendoza, Río Negro, and Neuquén. It is the youngest formation within the Neuquén Group and belongs to the Río Colorado Subgroup...
in Río Negro Province
Río Negro Province
Río Negro is a province of Argentina, located at the northern edge of Patagonia. Neighboring provinces are from the south clockwise Chubut, Neuquén, Mendoza, La Pampa and Buenos Aires. To the east lies the Atlantic Ocean.Its capital is Viedma...
of Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
, which is considered to be early Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
in age or about 83-80 million years old. Several skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
fragments were described, including a braincase and a mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...
(lower jaw). Other bones referred to this dinosaur include neck and tail vertebrae, rib
Rib
In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...
s, and numerous limb bones. One femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
(thigh bone) is over 6 feet (1.85 meters) tall, which has been used to extrapolate a mass of about 34 metric tonnes, or nearly 75,000 pounds
Pound (mass)
The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...
.
These bones were for the most part not associated with each other but scattered throughout the formation. Consequently, many scientists believe that they may not all belong to the same type of animal. In particular, the very square lower jaw has frequently been suggested to belong to a rebbachisaurid sauropod similar to Nigersaurus
Nigersaurus
Nigersaurus is a genus of diplodocoid sauropod dinosaur from the middle Cretaceous period, about 119 to 99 million years ago during the Aptian or Albian age. This dinosaur was described by Paul Sereno and colleagues in 1999...
. However the jaw of Bonitasaura
Bonitasaura
Bonitasaura is a titanosaurian dinosaur hailing from uppermost layers of the Late Cretaceous Bajo de la Carpa Formation, Neuquen Group, located in Río Negro Province, Northwestern Patagonia, Argentina...
is similar in overall shape and is clearly associated with titanosaur skeletal remains, indicating that the lower jaw may belong to Antarctosaurus wichmannianus after all. The back of the skull and the remainder of the skeleton are usually regarded as titanosaurian, although they do not necessarily belong to the same type of titanosaur. A. wichmannianus (minus the lower jaw) has been regarded as a lithostrotian, a group which includes armored titanosaurs, although no armor scutes were associated with its remains. This species has also been regarded as a possible nemegtosaurid titanosaur.
Antarctosaurus giganteus
Von Huene named a second species of Antarctosaurus in 1929, which he called A. giganteus because of its enormous size. Very few remains are known of this species and it is regarded as a nomen dubiumNomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
by some. The most famous of these bones are two gigantic femora, which are among the largest of any known sauropod. They measure about 7.75 feet (2.35 meters) in length. Extrapolating from the size of these bones has led to a mass estimate of approximately 69 metric tonnes (152,000 pounds) in one study, just a little smaller than the gigantic Argentinosaurus
Argentinosaurus
Argentinosaurus is a genus of titanosaur sauropod dinosaur first discovered by Guillermo Heredia in Argentina. The generic name refers to the country in which it was discovered...
, which at nearly 73 metric tonnes (160,000 pounds) would have been the heaviest known land animal of all time.
The bones mentioned above were recovered in Neuquén Province
Neuquén Province
Neuquén is a province of Argentina, located in the west of the country, at the northern end of Patagonia. It borders Mendoza Province to the north, Rio Negro Province to the southeast, and Chile to the west...
of Argentina, from the Plottier Formation
Plottier Formation
The Plottier Formation is a geologic formation that outcrops in the Argentine Patagonian provinces of Río Negro and Neuquén. It is the younger of two formations belonging to the Río Neuquén Subgroup within the Neuquén Group, with the oldest rocks dating from the late Coniacian and its youngest...
, which dates to the late Coniacian
Coniacian
The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series and spans the time between 89.3 ± 1 Ma and 85.8 ± 0.7 Ma...
stage of the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
Period, or about 87 to 85 million years ago. The Plottier, like the younger Anacleto, is a member of the Neuquén Group
Neuquén Group
The Neuquén Group is a group of geologic formations found in Argentina. Rocks in the Neuquén Group fall within the Cenomanian to early Campanian stages of the Late Cretaceous Period, about 100 million to 80 million years in age...
.
As so little is known of this animal, and because the material assigned to A. wichmannianus is so confused, A. giganteus cannot be confidently assigned to the genus Antarctosaurus at this time.
"Antarctosaurus" septentrionalis
In 1933, von Huene and Charles Matley described another species from IndiaIndia
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
. This species does preserve important anatomical information but does not belong to Antarctosaurus. It was renamed Jainosaurus
Jainosaurus
Jainosaurus is a large titanosaurian dinosaur of India and wider Asia, which lived in the Maastrichtian ....
in 1994.
"Antarctosaurus" jaxartensis
A single femur from KazakhstanKazakhstan
Kazakhstan , officially the Republic of Kazakhstan, is a transcontinental country in Central Asia and Eastern Europe. Ranked as the ninth largest country in the world, it is also the world's largest landlocked country; its territory of is greater than Western Europe...
forms the basis of this species, which was named by Soviet paleontologist Anatoly Riabinin in 1939. It is regarded as a nomen dubium today but is almost certainly not a species of the South American Antarctosaurus.
"Antarctosaurus" brasiliensis
Remains of this dinosaur, including two fragmentary limb bones and a partial vertebra, were found in the Bauru Formation of BrazilBrazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
and described by Arid and Vizzotto in 1971. This species is also considered a nomen dubium.
External links
- Post on the Dinosaur Mailing List detailing the various species of Antarctosaurus and the remains assigned to them.