| Neuquensaurus | |
|---|---|
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| Neuquensaurus skeletal mount in theDinosaurios más allá de la extinción exhibition | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Clade: | †Titanosauria |
| Family: | †Saltasauridae |
| Tribe: | †Saltasaurini |
| Genus: | †Neuquensaurus Powell,1992 |
| Type species | |
| †Titanosaurus australis Lydekker, 1893 | |
| Species | |
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| Synonyms | |
Genus synonymy
Species synonymy
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Neuquensaurus (meaning "Neuquén lizard") is agenus ofsaltasauridsauropoddinosaur that lived in the LateCretaceous, about 80 million years ago inArgentina in South America. Its fossils were recovered from outcrops of theAnacleto Formation aroundCinco Saltos, near the Neuquén river from which its name is derived.
In 1893,Richard Lydekker namedTitanosaurus australis, based on a series of caudal vertebrae and limb elements. The remains had been found bySantiago Roth and F. Romero in theNeuquén Province ofArgentina at the Neuquén River, and were by Lydekker assigned to a single individual.[1] Six caudal vertebrae, with the inventory numbers MLP Ly 1-6-V-28-1, were theholotype of the species. They had probably been found in a layer of theAnacleto Formation.
Some elements that had been referred toTitanosaurus australis were reassigned toLaplatasaurus araukanicus byFriedrich von Huene in 1929.[1] The same year, von Huene named aTitanosaurus robustus, and claimed it differed fromT. australis in the limb material. Von Huene described all the slender limb material toT. australis, but did not identify any differentiating features between the vertebrae.[2] When describingT. robustus, von Huene did not really compare other genera and species to it.[1] From thesyntype material assigned by von Huene toT. robustusJosé Fernando Bonaparteet al. in 1978 chose fourlectotypes, specimens MLP 26-250, MLP 26-252, MLP 26-254, and MLP 26-259, a left femur, both ulnae, and a left radius.[3][1]
In 1986,Jaime Eduardo Powell, concluding thatTitanosaurus australis was less similar thanLaplatasaurus araukanicus toTitanosaurus indicus, named a separate genus:Neuquensaurus.[4] However, he did so in an unpublished dissertation which causedNeuquensaurus australis andNeuquensaurus robustus to remain invalidnomina ex dissertatione. In 1990, the two species were assigned toSaltasaurus byJohn Stanton McIntosh, as aSaltasaurus australis and aSaltasaurus robustus, claiming that the features found by Bonaparte were not of sufficient taxonomic importance to justify a generic separation.[1]
In 1992 Powell validly namedNeuquensaurus, with astype speciesTitanosaurus australis of which thecombinatio nova then isNeuquensaurus australis. He also foundTitanosaurus robustus to be assignable to the new genus, but considered it non-diagnostical, and so anomen dubium.[5]
This dinosaur is believed to have possessed armor-like osteoderms. A relatively small sauropod, with a femur only 0.75 metres (2.5 ft) long. It is one of the most completely known of Patagonian sauropods,[1] measuring 7–9 metres (23–30 ft) long and weighing 1.8–3.5 metric tons (2.0–3.9 short tons).[6][7] 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).[8]
Cervical vertebrae are known from multiple specimens ofNeuquensaurus, although few are definitively associated with any other material. The centra are elongate, compressed vertically, and stronglyopisthocoelous, with an ovoidpleurocoel and rounded neural spine. Diagnostic ofSaltasaurinae, theprezygapophyses are shortened and robust and thepostzygapophyses extend far posteriorly to compensate. The lateral projections of the neural arch (transverse processes) are far more robust than inIsisaurus.[8] 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 ofNeuquensaurus are proportionally taller than inTrigonosaurus orLirainosaurus. 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 thehyposphene-hypantrum articulations of non-titanosaurs that limit vertebral motion. Two accessorylaminae are present in the dorsals ofNeuquensaurus that are absent even in the close relativesSaltasaurus andRocasaurus. Unique among all sauropods, thesacrum ofNeuquensaurus is composed of seven vertebrae. The last vertebra is convex anteriorly and posteriorly, and diagnostically the middle vertebrae are strongly compressed in width.[8] Like other derived titanosaurs, allcaudal vertebrae ofNeuquensaurus are stronglyprocoelous and vertically compressed. There is a prominent ventral depression like inSaltasaurus andRocasaurus, 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.[8]
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 inOpisthocoelicaudia. In general aspect, the scapula resemblesSaltasaurus,Opisthocoelicaudia,Lirainosaurus, andAlamosaurus. The coracoids of the scapulae are roughly quadrangular in shape, and are alikeSaltasaurus andLirainosaurus, but notOpisthocoelicaudia,Rapetosaurus, orIsisaurus, all of which have a rounded coracoid.[1]
Many characters distinguishNeuquensaurus 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.[1]
Neuquensaurus is a derivedsaltasaurine. Its closest relatives wereSaltasaurus,Rocasaurus, andBonatitan, and together they made up Saltasaurinae.[1]
The cladogram from Rubilar-Rogerset al. (2021) is shown below:[9]
Neuquensaurus is known from fossils from theAnacleto Formation.[1]
