Neuquensaurus Australis
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''Neuquensaurus'' (meaning "
Neuquén Neuquén (; arn, Nehuenken) is the capital city of the Argentine province of Neuquén and of the Confluencia Department, located in the east of the province. It occupies a strip of land west of the confluence of the Limay and Neuquén rivers w ...
lizard") is a
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
saltasaurid 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, Asia, North America, and Europe. Th ...
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 bo ...
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
that lived in the Late
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
, about 80 million years ago in
Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
and
Uruguay Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental del Uruguay), is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast; while bordering ...
in South America. Its fossils were recovered from outcrops of the
Anacleto Formation The Anacleto Formation is a geologic formation with outcrops in the Argentina, Argentine Patagonia, Patagonian provinces of Mendoza Province, Mendoza, Río Negro Province, Río Negro, and Neuquén Province, Neuquén. It is the youngest formation w ...
around
Cinco Saltos Cinco Saltos is a city in the provinces of Argentina, province of Río Negro Province, Río Negro, Argentina, located on the eastern side of the valley of the Neuquén River, near the Pellegrini Lake, about from northwest of Neuquén and from All ...
, near the Neuquén river from which its name is derived.


History

In 1893,
Richard Lydekker Richard Lydekker (; 25 July 1849 – 16 April 1915) was an English naturalist, geologist and writer of numerous books on natural history. Biography Richard Lydekker was born at Tavistock Square in London. His father was Gerard Wolfe Lydekker, ...
named ''
Titanosaurus ''Titanosaurus'' (; ) is a dubious genus of sauropod dinosaurs, first described by Richard Lydekker in 1877.R. Lydekker. (1877). Notices of new and other Vertebrata from Indian Tertiary and Secondary rocks. ''Records of the Geological Survey of I ...
australis'', based on a series of caudal vertebrae and limb elements. The remains had been found by
Santiago Roth Santiago Roth (14 June 1850 – 4 August 1924) was a Swiss Argentine paleontologist and academic known for his fossil collections and Patagonian expeditions. Life Kaspar Jakob (Spanish: Santiago) was born and raised in Herisau, Canton Appenzell ...
and F. Romero in the
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. It also meets La Pampa Province a ...
of
Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
at the Neuquén River, and were by Lydekker assigned to a single individual. Six caudal vertebrae, with the inventory numbers MLP Ly 1-6-V-28-1, were the
holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...
of the species. They had probably been found in a layer of the
Anacleto Formation The Anacleto Formation is a geologic formation with outcrops in the Argentina, Argentine Patagonia, Patagonian provinces of Mendoza Province, Mendoza, Río Negro Province, Río Negro, and Neuquén Province, Neuquén. It is the youngest formation w ...
. Some elements that had been referred to ''Titanosaurus australis'' were reassigned to '' Laplatasaurus araukanicus'' by
Friedrich von Huene Friedrich von Huene, born Friedrich Richard von Hoinigen, (March 22, 1875 – April 4, 1969) was a German paleontologist who renamed more dinosaurs in the early 20th century than anyone else in Europe. He also made key contributions about v ...
in 1929. The same year, von Huene named a ''Titanosaurus robustus'', and claimed it differed from ''T. australis'' in the limb material. Von Huene described all the slender limb material to ''T. australis'', but did not identify any differentiating features between the vertebrae. When describing ''T. robustus'', von Huene did not really compare other genera and species to it. From the
syntype In biological nomenclature, a syntype is any one of two or more biological types that is listed in a description of a taxon where no holotype was designated. Precise definitions of this and related terms for types have been established as part of ...
material assigned by von Huene to ''T. robustus'' José Fernando Bonaparte ''et al.'' in 1978 chose four
lectotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...
s, specimens MLP 26-250, MLP 26-252, MLP 26-254, and MLP 26-259, a left femur, both ulnae, and a left radius. In 1986, Jaime Eduardo Powell, concluding that ''Titanosaurus australis'' was less similar than ''Laplatasaurus araukanicus'' to ''Titanosaurus indicus'', named a separate genus: ''Neuquensaurus''. However, he did so in an unpublished dissertation which caused ''Neuquensaurus australis'' and ''Neuquensaurus robustus'' to remain invalid ''nomina ex dissertatione''. In 1990, the two species were assigned to ''
Saltasaurus ''Saltasaurus'' (which means "lizard from Salta") is a genus of saltasaurid dinosaur of the Late Cretaceous period of Argentina. Small among sauropods, though still heavy by the standards of modern creatures, ''Saltasaurus'' was characterized by ...
'' by
John Stanton McIntosh John is a common English name and surname: * John (given name) * John (surname) John may also refer to: New Testament Works * Gospel of John, a title often shortened to John * First Epistle of John, often shortened to 1 John * Second E ...
, as a ''Saltasaurus australis'' and a ''Saltasaurus robustus'', claiming that the features found by Bonaparte were not of sufficient taxonomic importance to justify a generic separation. In 1992 Powell validly named ''Neuquensaurus'', with as
type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...
''Titanosaurus australis'' of which the ''
combinatio nova ''Combinatio nova'', abbreviated ''comb. nov.'' (sometimes ''n. comb.''), is Latin for "new combination". It is used in taxonomic biology literature when a new name is introduced based on a pre-existing name. The term should not to be confused wi ...
'' then is ''Neuquensaurus australis''. He also found ''Titanosaurus robustus'' to be assignable to the new genus, but considered it non-diagnostical, and so 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 s ...
''.J.E. Powell, 1992, "Osteologia de ''Saltasaurus loricatus'' (Sauropoda - Titanosauridae) del Cretácico Superior del noroeste Argentino" In: J.L. Sanz & A.D. Buscalioni (eds.), ''Los Dinosaurios y Su Entorno Biotico: Actas del Segundo Curso de Paleontologia in Cuenca. Institutio "Juan de Valdes", Cuenca, Argentina'' pp 165-230


Description

This dinosaur is believed to have possessed armor-like osteoderms. A relatively small sauropod, with a femur only long. It is one of the most completely known of Patagonian sauropods. In addition to the original fossils described by Lydekker in 1893, it is represented by fossils collected in the early twentieth century, and more recent material, including a well preserved and partially articulated specimen described in 2005 (with two associated osteoderms).
Cervical vertebrae In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...
are known from multiple specimens of ''Neuquensaurus'', although few are definitively associated with any other material. The centra are elongate, compressed vertically, and strongly , with an ovoid and rounded neural spine. Diagnostic of
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 ne ...
, the are shortened and robust and the extend far posteriorly to compensate. The lateral projections of the neural arch (transverse processes) are far more robust than in ''
Isisaurus ''Isisaurus'' (named after the Indian Statistical Institute) is a genus of titanosaurian dinosaur from the Late Cretaceous Lameta Formation of India. The genus contains a single species, ''Isisaurus colberti''. Discovery and Naming The type spe ...
''. As in the cervicals, the dorsal vertebrae bear strongly opisthocoelous centra with lateral pneumatic openings. In the dorsals, however, the pleurocoels are posteriorly pinched and internally subdivided, a regular feature of titanosaurs. The pleurocoels of ''Neuquensaurus'' are proportionally taller than in '' Trigonosaurus'' or ''
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 ...
''. A ventral keel is lost throughout the dorsal series of probably 10 vertebrae, although the total count is uncertain. The vertebrae also lean less posteriorly towards the pelvis, initially inclined far beyond their individual centrum. However, they lack the of non-titanosaurs that limit vertebral motion. Two accessory are present in the dorsals of ''Neuquensaurus'' that are absent even in the close relatives ''Saltasaurus'' and ''
Rocasaurus ''Rocasaurus'' (meaning "General Roca lizard") is a genus of titanosaurian sauropod that lived in South America. ''Rocasaurus'' was discovered in Argentina in 2000, within the Allen Formation which is dated to be middle Campanian to early Maastr ...
''. Unique among all sauropods, the
sacrum The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part ...
of ''Neuquensaurus'' is composed of seven vertebrae. The last vertebra is convex anteriorly and posteriorly, and diagnostically the middle vertebrae are strongly compressed in width. Like other derived titanosaurs, all
caudal vertebrae The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
of ''Neuquensaurus'' are strongly and vertically compressed. There is a prominent ventral depression like in ''Saltasaurus'' and ''Rocasaurus'', but contrasting the other genera there is no ridge dividing this depression. Additionally, the neural spines of vertebrae become progressively more reclined, and a prespinal lamina is present in all vertebrae. ''Neuquensaurus'' has an almost complete skeleton. Among the preserved elements are a scapula. The scapula is co-ossified with the coracoid, a feature also found in ''
Opisthocoelicaudia ''Opisthocoelicaudia'' is a genus of sauropod dinosaur of the late Cretaceous, Late Cretaceous Period discovered in the Gobi Desert of Mongolia. The type species is ''Opisthocoelicaudia skarzynskii''. A well-preserved skeleton lacking only the ...
''. In general aspect, the scapula resembles ''Saltasaurus'', ''Opisthocoelicaudia'', ''
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 ''
Alamosaurus ''Alamosaurus'' (; meaning "Ojo Alamo lizard") is a genus of opisthocoelicaudiine titanosaurian sauropod dinosaurs, containing a single known species, ''Alamosaurus sanjuanensis'', from the late Cretaceous Period of what is now southern North Am ...
''. The coracoids of the scapulae are roughly quadrangular in shape, and are alike ''Saltasaurus'' and ''Lirainosaurus'', but not ''Opisthocoelicaudia'', ''
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 ...
'', or ''
Isisaurus ''Isisaurus'' (named after the Indian Statistical Institute) is a genus of titanosaurian dinosaur from the Late Cretaceous Lameta Formation of India. The genus contains a single species, ''Isisaurus colberti''. Discovery and Naming The type spe ...
'', all of which have a rounded coracoid. Many characters distinguish ''Neuquensaurus'' from other titanosaurians. The features found by Otero in 2010 are: the possession of posterior caudal centra that are dorsoventrally flattened, and strongly developed fibular lateral tuberosity.


Classification

''Neuquensaurus'' is a derived saltasaurine. Its closest relatives were ''
Saltasaurus ''Saltasaurus'' (which means "lizard from Salta") is a genus of saltasaurid dinosaur of the Late Cretaceous period of Argentina. Small among sauropods, though still heavy by the standards of modern creatures, ''Saltasaurus'' was characterized by ...
'', ''
Rocasaurus ''Rocasaurus'' (meaning "General Roca lizard") is a genus of titanosaurian sauropod that lived in South America. ''Rocasaurus'' was discovered in Argentina in 2000, within the Allen Formation which is dated to be middle Campanian to early Maastr ...
'', and ''
Bonatitan ''Bonatitan'' is a genus of titanosaurian dinosaur from the Late Cretaceous Allen Formation of Argentina. It was named in 2004. Description The type species is ''Bonatitan reigi'', first described by Martinelli and Forasiepi in 2004. The speci ...
'', and together they made up Saltasaurinae. The cladogram from Rubilar-Rogers ''et al.'' (2021) is shown below:


Paleoecology

''Neuquensaurus'' is known from fossils from the
Anacleto Formation The Anacleto Formation is a geologic formation with outcrops in the Argentina, Argentine Patagonia, Patagonian provinces of Mendoza Province, Mendoza, Río Negro Province, Río Negro, and Neuquén Province, Neuquén. It is the youngest formation w ...
.


References


External links

{{Taxonbar, from=Q284931 Saltasaurids Late Cretaceous dinosaurs of South America Anacleto Formation Cretaceous Argentina Fossils of Argentina Cretaceous Uruguay Fossils of Uruguay Fossil taxa described in 1992 Taxa named by Jaime Powell