Antarctosaurus (/ænˌtɑːrktoʊˈsɔːrəs/; meaning "southern lizard") is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period of what is now South America. The type species, Antarctosaurus wichmannianus, and a second species, Antarctosaurus giganteus, were described by prolific German paleontologist Friedrich von Huene in 1929. Three additional species of Antarctosaurus have been named since then but later studies have considered them dubious or unlikely to pertain to the genus.
The type species, A. wichmannianus, is controversial because there is uncertainty as to whether all the described remains belong to the same individual or even genus. The second species, A. giganteus, is considered dubious, but the fragmentary remains represent one of the largest dinosaurs known.
|Hypothetical Antarctosaurus wichmannianus skull diagram showing the bones illustrated by von Huene in 1929. It's not certain that the mandible and braincase belong to the same individual or even same genus.|
von Huene, 1929
Remains of this dinosaur were first mentioned in print in 1916, although they were not fully described and named until a 1929 monograph written by paleontologist Friedrich von Huene. 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.
Antarctosaurus wichmannianus is the type species of the genus, named in 1929 after the discoverer of its remains in 1912, geologist Ricardo Wichmann. Von Huene used the name A. wichmannianus to describe a large assemblage of bones, which are considered to come from the Anacleto Formation in Río Negro Province of Argentina, which is probably early Campanian in age. Two additional limb bones, found in the Chubut Province in 1924, were also referred to A. wichmannianus by von Huene in 1929. Later studies, however, have doubted their referral to the species.
Von Huene also named a fragmentary second species of Antarctosaurus in the same 1929 monograph, which he tentatively called cf. Antarctosaurus giganteus because of its enormous size. These fossils were recovered in Neuquén Province of Argentina, from the Plottier Formation, which dates to the Coniacian-Santonian stages of the Late Cretaceous Period. The Plottier, like the younger Anacleto, is a member of the Neuquén Group.
Very few remains are known of this species and it is regarded as a nomen dubium by some. Other researchers regard A. giganteus as a likely valid species but probably belonging to a new genus. In 1969, Leigh van Valen considered A. wichmannianus and A. giganteus to be growth stages of the same species and favored the name A. giganteus. This idea is problematic because A. wichmannianus was named earlier in the same paper and it is known from more material, it should, therefore, get priority over A. giganteus. The two species are also not from the same geological formation which suggests they did not belong to the same time period.
In 1933, Von Huene and Charles Matley described another species, Antarctosaurus septentrionalis, meaning "northern". The remains were found in the Lameta Formation of Madhya Pradesh State in India. This species does preserve important anatomical information but has been assigned to its own genus in 1994; Jainosaurus.
Antarctosaurus jaxarticus from Kazakhstan is known from a single femur. It was named by Soviet paleontologist Anatoly Riabinin in 1938, and was the first sauropod species from Kazakhstan. It was reported from a certain locality in the Kyzylkum Desert, but the exact location is unknown. It may have come from the Syuksyuk Formation (originally described as Dabrazinskaya Svita) which dates to the Santonian stage of the Late Cretaceous. Other researchers have considered it as either, Titanosauridae incertae sedis, as a nomen dubium, or as a nomen nudem.
In 1970, two fragmentary limb bones and a partial vertebra were found in the Adamantina Formation (originally described as Bauru Formation; has also been reported as the São José do Rio Preto Formation) of the northern Paraná Basin in Brazil. The remains were described by their discoverers Fahad Moysés Arid and Luiz Dino Vizotto in 1971 as A. brasiliensis. Other researchers have considered this species as either, a nomen dubium, or an indeterminate titanosaur.
Antarctosaurus is a problematic genus because none of the species described are known from complete remains and the type species consists of elements that are of questionable association which has caused a confused taxonomy. Of the four additional species that have been assigned to Antarctosaurus over the years, three have been considered dubious and "Antarctosaurus" septentrionalis, was given its own genus, Jainosaurus.
The remains that have been described belong to sauropods, most probably titanosaurs, a group of large-bodied, quadrupedal herbivores, usually possessing a long neck and tail, with a small head.
The assemblage of fossil remains that became known as A. wichmannianus were given the specimen number MACN 6904. The known material includes several skull fragments, including a braincase and an incomplete mandible (lower jaw), a cervical (neck) vertebra, a caudal (tail) vertebra, rib fragments, and numerous limb bones including a femur which measures 1.39 meters (4.6 ft) tall. None of the individual fossils were designated the holotype specimen so MACN 6904 is considered to be an assemblage of syntypes. The total length of A. wichmannianus has been estimated at around 17 meters (56 ft).
An additional femur and tibia were also referred by von Huene to A. wichmannianus; the femur, FMNH P13019, is over 1.85 meters (6.1 ft) tall. In one study the dimensions of this femur were used in a regression analysis to estimate the mass of A. wichmannianus at about 34 metric tons (37 short tons). The referral of the additional femur and tibia has been questioned by later researchers. In 2003 Jaime Eduardo Powell tentatively referred them to cf. Argyrosaurus and in 2012 Philip Mannion and Alejandro Otero considered it an indeterminate titanosaur.
The incomplete mandible attributed to A. wichmannianus is squared off at the front with each dentary bone being ''L'' shaped. The teeth were restricted to the front of the lower jaw and were small and slender. The squared off jaws suggest specialised feeding habits, such as feeding near a surface plane like low vegetation on the ground or floating plants in water.
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, described in 2004, is similar in overall shape and is clearly associated with titanosaur skeletal remains, indicating that the lower jaw may belong to A. wichmannianus after all. In 2013 and 2019 respectively, Brasilotitan and Baalsaurus were described which also possessed squared off jaws. It was noted that Brazilotitan, Bonitasaura, Antarctosaurus, and other titanosaurs show up three teeth per alveolus (tooth socket) whereas the rebbachisaurid Nigersaurus shows up to seven teeth. Brazilotitan and Baalsaurus were described as a titanosaurs, closely related to A. wichmannianus.
The back of the skull and the remainder of the skeleton are usually regarded as titanosaurian by researchers, although they do not necessarily belong to the same type of titanosaur. In 2005, Jeffrey Wilson considered the braincase as being referable to Nemegtosauridae but noted that other skull remains require further study. A study, published in 2012 by Ariana Paulina Carabajal, CT scanned the A. wichmannianus braincase which revealed the complete brain endocast and the inner ear structures. The brain endocast and inner ear share several features with other titanosaurids such as short olfactory tracts and olfactory bulbs that are horizontally projected.
Powell compared the width of the cranium to the length of the limb bones of both A. wichmannianus and Saltasaurus; this led him to conclude that the skull was proportionally small in A. wichmannianus, this might imply that the skull and limb elements could belong to different individuals or a different taxa. He noted, however, that the comparison was potentially misleading because the overall anatomy of Saltasaurus is shorter and stouter which might facilitate a bigger skull.
Von Huene assigned two tarsal (ankle) bones to A. wichmannianus, which he described as an astragalus and a calcanium. Powell suggested it's possible that the calcanium described by von Huene is actually the astragalus of a smaller individual. He also noted that the astragalus seems too small to belong to the same individual as the tibia, being only about half the width.
Von Huene described a caudal vertebra which was found close to the skull material. This vertebra was the first caudal, belonging to the base of the tail just after the sacrum (vertebrae attached to the hip). The vertebra features a biconvex centrum, a feature shared with other titanosaurs. Von Huene noted that the first caudal could possibly belong to Laplatasaurus.
With the exception of an incomplete cervical vertebra and the questionable first caudal, there are no vertebrae that link the skull to the limb material. There is a lack of field documentation to aid in the referral of all the material to one individual. Powell thought it was probable that von Huene correctly assigned the material to A. wichmannianus, arguing that von Huene would have been able to communicate with the discoverers and would have had access to photographs of the discovery site.
The type specimen of A. giganteus, MLP 26-316, includes a left and right femur, a partial left and right pubis, the distal end of a damaged tibia, numerous rib and distal caudal vertebrae fragments, and six large and unidentifiable bones. The two gigantic femora measure 2.35 meters (7.7 ft) in length, which are among the largest of any known sauropod. Even though the femurs are large, they are also somewhat gracile in construction.
A reconstruction of A. giganteus, published in 1956 by Carlos Rusconi, was given a length around 30 meters (98 ft). In 1969, van Valen considered it as similar in size to Giraffatitan brancai (then called Brachiosaurus brancai). Based on an earlier mass estimate of G. brancai by Edwin Harris Colbert in 1962, van Valen gave A. giganteus an estimated mass of about 80 metric tons (88 short tons). In 1994, Gregory S. Paul estimated the weight of both A. giganteus and Argentinosaurus at between 80 and 100 metric tons (88 and 110 short tons) and lengths of 30 to 35 meters (98 to 115 ft) long. Extrapolating from the femur's dimensions, a 2004 study by Gerardo Mazzetta and colleagues estimated the mass of A. giganteus at approximately 69 metric tons (76 short tons); slightly smaller than Argentinosaurus which in the same study was estimated at nearly 73 metric tons (80 short tons). This would make A. giganteus among the heaviest known land animals. In 2006, Kenneth Carpenter used the short-necked Saltasaurus as a guide and estimated a shorter length of 23 meters (75 ft) long. Due to the incompleteness of the remains, any size estimates are subject to a large amount of error.
"Antarctosaurus" jaxarticus and "Antarctosaurus" brasiliensis are both known from very fragmentary remains.
"Antarctosaurus" jaxarticus is known from a single femur which was briefly reported as resembling a femur attributed to Jainosaurus (then called "Antarctosaurus" septentrionalis). Paleontologist Teresa Maryańska noted that, whilst A. jaxarticus was named, it was not properly described or diagnosed. The femur possibly belongs to the titanosaur clade Lithostrotia.
The type specimen of "Antarctosaurus" brasiliensis is only known from three fragmentary bones that are titanosaurian in nature; a partial left femur GP-RD-2, a partial right humerus GP-RD-3, and an incomplete dorsal vertebra (backbone) GP-RD-4. The femur is 1.15 meters (3.8 ft) preserved and was estimated at 1.55 meters (5.1 ft) if it were completed. The humerus is 65 centimeters (2.13 ft) preserved and estimated at 95 centimeters (3.12 ft) completed. The dorsal vertebra centrum is 17 centimeters (6.7 in) long.
Argyrosaurus ( AR-jy-ro-SOR-əs) is a genus of herbivorous titanosaurian sauropod dinosaur that lived about 90 million years ago, during the Late Cretaceous Period of what is now Argentina.Baalsaurus
Baalsaurus (named after the dinosaur fossil site Baal in Argentina, which in turn is named after the ancient Phoenician god Baal) is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous of Neuquén Province, Patagonia, Argentina. The type and only known species is B. mansillai, with the specific name honoring the discoverer Juan Eduardo Mansilla, a museum technician at the Geology and Paleontology Museum of the National University of Comahue.
The holotype specimen, MUCPv-1460, is a mostly complete right dentary that was found in rocks of the upper Portezuelo Formation. The dentary is squared-off instead of curved when viewed from above or below, with the teeth crowded into the front of the jaw, making it similar to the jaw of Antarctosaurus, Brasilotitan, and to a lesser extent Bonitasaura. The specimen is currently held at the Geology and Paleontology Museum of the National University of Comahue, Parque Natural Geo-Paleontológico Proyecto Dino, Barreales Lake.Baurutitan
Baurutitan is a genus of sauropod dinosaur that lived during the Late Cretaceous in what is now Brazil. The type species, Baurutitan britoi, was described in 2005 by Kellner and colleagues, although the fossil remains had already been discovered in 1957. Baurutitan is classified as a lithostrotian titanosaur, and is distinguished from related genera based on its distinctive caudal vertebrae. This South American dinosaur was found in the Marília Formation near Uberaba, in the Brazilian state of Minas Gerais.Bonitasaura
Bonitasaura is a 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, Argentina. The remains, consisting of a partial sub-adult skeleton jumbled in a small area of fluvial sandstone, including lower jaw with teeth, partial vertebrae series and limb bones, were described by Sebastian Apesteguía in 2004.
The genus name Bonitasaura refers to the fossil quarry’s name, "La Bonita", while the name of the type species, B. salgadoi, pays homage to Leonardo Salgado, a renowned Argentine palaeontologist.Brasilotitan
Brasilotitan is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous (early Maastrichtian) Adamantina Formation of Brazil. The type species is Brasilotitan nemophagus.Daxiatitan
Daxiatitan is a genus of titanosaur dinosaur from the Lower Cretaceous of Lanzhou Basin, Gansu Province, northwestern China. It is known from fossils including several neck vertebrae, a shoulder blade, and a thigh bone.It was a very large dinosaur, estimated at 23–30 meters (75–98 feet). Like both Euhelopus and Huanghetitan, it had an enormously long neck.Elaltitan
Elaltitan is an extinct genus of large lithostrotian titanosaur sauropod known from the Late Cretaceous (mid Cenomanian to Turonian stage) of Chubut Province, southern Argentina. It contains a single species, Elaltitan lilloi.Epachthosaurus
Epachthosaurus (meaning "heavy lizard") was a genus of dinosaur from the Late Cretaceous. It was a titanosaurid sauropod. Its fossils have been found in Central and Northern Patagonia in South America.Flagellicaudata
Flagellicaudata is a clade of Dinosauria. It belongs to Sauropoda and includes two families, the Dicraeosauridae and the Diplodocidae.Gravisauria
Gravisauria is a clade of sauropod dinosaurs consisting of some genera, Vulcanodontidae and Eusauropoda.Huangshanlong
Huangshanlong is a genus of mamenchisaurid dinosaurs native to the Anhui province of China. It contains a single species, Huangshanlong anhuiensis. H. anhuiensis represents, along with Anhuilong and Wannanosaurus, one of three dinosaurs fround in Anhui province.Indroda Dinosaur and Fossil Park
The Indroda Dinosaur and Fossil Park in Ahmedabad in the state of Gujarat, India, is a park which houses the fossilized remains and the petrified eggs of the dinosaurs. It is technically a man made fossil park and not the actual nesting grounds where the dinosaurs lived. The eggs and fossils on display here are actually from the world's 3rd largest dinosaur fossil excavation site and 2nd largest hatchery located at Raiyoli, Balasinor, Gujarat. The Park was set up by the Geological Survey of India and is the only dinosaur museum in the country.The Park is run by the Gujarat Ecological and Research Foundation (GEER) and has been called India's Jurassic Park. The oldest record of dinosaur bone fossils is of middle Jurassic period and they are found from Parcham formation of Kutch basin. The fossils which were found in Upper Cretaceous formations in the region date back 66 million years ago. The eggs are of different sizes, some the size of cannon balls. Fossil trackways of these gargantuan animals are also on display in the park.Dinosaurs that are on display include Tyrannosaurus rex, Megalosaurus, Titanosaurus, Barapasaurus, Brachiosaurus, Antarctosaurus, Stegosaurus and Iguanodon. The park displays life-size models of the dinosaurs along with details of each period in which they existed and characteristics of the animals.The fossils were found in the Songhir Bagh Basin, the Himatnagar basin of Balasinor, south-eastern parts of Kheda, Panchmahal and Vadodara districts of the state.Isisaurus
Isisaurus (named after the Indian Statistical Institute) is a genus of dinosaur from the Late Cretaceous Period. Isisaurus was a sauropod (specifically a titanosaur), which lived in what is now India.Jainosaurus
Jainosaurus is a large titanosaurian dinosaur of India and wider Asia, which lived in the Maastrichtian (approximately 68 million years ago). A herbivorous quadruped, an adult Jainosaurus would have measured around eighteen metres long and held its head six metres high. No accurate estimate of the weight has yet been made. The humerus of the type specimen is 134 centimetres long.Kaijutitan
Kaijutitan (meaning "Kaiju titan" after the type of Japanese movie monsters) is a genus of basal titanosaur dinosaur from the Sierra Barrosa Formation from Neuquén Province in Argentina. The type and only species is Kaijutitan maui.Laplatasaurus
Laplatasaurus (meaning "La Plata lizard", named for La Plata, Argentina) is a genus of titanosaurian sauropod dinosaur that lived during the Late Cretaceous in South America.
The genus was named in 1927 by Friedrich von Huene, but without a description, so that it remained a nomen nudum. In 1929 the type species, Laplatasaurus araukanicus, was described by Huene. The generic name refers to La Plata. The specific name is derived from the Araucanos or Mapuche. By accident Huene in 1929 also mentioned a "Laplatasaurus wichmannianus" but that was a lapsus calami for Antarctosaurus wichmannianus. In 1933 however, he and Charles Alfred Matley renamed Titanosaurus madagascariensis to Laplatasaurus madagascariensis. This last species is today commonly referred to the original Titanosaurus.
Huene based Laplatasaurus on fragmentary material found in three locations in Argentina, in strata of the Allen Formation, dating from the Campanian faunal stage. It consisted of limb elements, some dorsal vertebrae and a series of caudal vertebrae. Part of the finds had earlier been referred by Richard Lydekker to Titanosaurus australis. Huene never assigned a holotype, but in 1979 José Fernando Bonaparte chose MLP 26-306 as the lectotype, a specimen consisting of a tibia and a fibula that perhaps originate from different individuals.
Huene assigned those fossils to Laplatasaurus that seemed to indicate a rather large yet at the same time elegantly built sauropod. The about eighteen metres (60 ft) long Laplatasaurus was perhaps similar to Saltasaurus. Osteoderms forming an armored plating on the back, have been referred to Laplatasaurus but the association is uncertain. These plates had much smaller ridges than those of Saltasaurus.
Huene placed Laplatasaurus in the Titanosauridae, which is still a common classification. In his 2003 review of South American titanosaurs, Jaime Eduardo Powell assigned Laplatasaurus to Titanosaurus, creating the new combination Titanosaurus aurakanicus. Others however, continued to treat Laplatasaurus as valid genus separate from Titanosaurus.A 2015 re-assessment of Laplatasaurus found it to be closely related to Bonitasaura, Futalognkosaurus, Mendozasaurus, and Uberabatitan. The genus was restricted to the lectotype, and the material from Rancho de Avila was assigned to cf. Bonitasaura sp.Lithostrotia
Lithostrotia is a clade of derived titanosaur sauropods that lived during the Early Cretaceous and Late Cretaceous. The group was defined by Unchurch et al. in 2004 as the most recent common ancestor of Malawisaurus and Saltasaurus and all the descendants of that ancestor. Lithostrotia is derived from the Ancient Greek lithostros, meaning "inlaid with stones", referring to the fact that many known lithostrotians are preserved with osteoderms. However, osteoderms are not a distinguishing feature of the group, as the two noted by Unchurch et al. include caudal vertebrae with strongly concave front faces (procoely), although the farthest vertebrae are not procoelous.Sohan Lal Jain
Sohan Lal Jain is an Indian paleontologist, who worked for many years at the Indian Statistical Institute, Kolkata. The large herbivorous sauropod dinosaur genus Jainosaurus, was named in his honour after it was identified as a distinct genus although initially thought to be a species of Antarctosaurus. His other major contributions to paleontology were in the study of sauropod braincases and some fossil turtles.Tambatitanis
Tambatitanis is an extinct genus of titanosauriform dinosaur from the Early Cretaceous (probably early Albian) of Japan. It is known from a single type species, Tambatitanis amicitiae. It was probably around 14 meters long and its mass was estimated at some 4 tonnes. It was a basal titanosauriform and possibly belonged to the Euhelopodidae.