Saltasaurus

Saltasaurus (which means "lizard from Salta") is a genus of titanosaurid sauropod dinosaur of the Late Cretaceous Period of Argentina. Small among sauropods, though still heavy by the standards of modern creatures, Saltasaurus was characterized by a short neck and stubby limbs. It was the first genus of sauropod known to possess armour of bony plates embedded in its skin. Such small bony plates, called osteoderms, have since been found on other titanosaurids.

Saltasaurus
Temporal range: Late Cretaceous, 85-70 Ma
Saltasaurus dinosaur
Life restoration
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Sauropodomorpha
Clade: Sauropoda
Clade: Titanosauria
Clade: Lithostrotia
Family: Saltasauridae
Genus: Saltasaurus
Bonaparte & Powell, 1980
Species:
S. loricatus
Binomial name
Saltasaurus loricatus
Bonaparte & Powell, 1980
Synonyms

Discovery

Saltasaurus
A large osteoderm

The fossils of Saltasaurus were excavated by José Fernando Bonaparte, Martín Vince and Juan C. Leal between 1975 and 1977 at the Estancia "El Brete". The find was in 1977 reported in the scientific literature.[1]

Saltasaurus was named and described by Bonaparte and Jaime E. Powell in 1980. The type species is Saltasaurus loricatus. Its generic name is derived from Salta Province, the region of north-west Argentina where the first fossils were recovered. The specific name means "protected by small armoured plates" in Latin.[2]

The holotype, PVL 4017-92, was found in a layer of the Lecho Formation dating from the early Maastrichtian stage of the Upper Cretaceous period, about seventy million years old. It consists of a sacrum connected to two ilia. Under the inventory number PVL 4017 over two hundred additional fossils have been catalogued. These include rear skull elements, teeth, vertebrae of the neck, back, hip and tail, parts of the shoulder girdle and the pelvis, and limb bones — plus various pieces of armour. These bones represent a minimum of five individuals, two adults and three juveniles or subadults.[3]

Currently the only recognised species of Saltasaurus is S. loricatus. A S. robustus and a S. australis have been suggested but these are now considered to belong to a separate genus, Neuquensaurus. Earlier, armour plates from the area had been named as Loricosaurus by Friedrich von Huene who assumed them to be from an armoured ankylosaurian. It has been suggested these plates were in fact from Saltasaurus.

Description

Saltasaurus environment
Saltasaurus herd passes Quilmesaurus and Noasaurus

Saltasaurus is very small compared to most other members of the Sauropoda. Powell estimated the adult length at six metres. In 2010, Gregory S. Paul estimated the maximum length at 8.5 metres, the weight at 2.5 tonnes.[4] However, Donald Henderson in 2013 estimated the animal at 12.8 metres (42 ft) in length and 6.87 tonnes (7.57 short tons) in weight.[5]

The teeth of Saltasaurus were cylindrical, with spatulate points. Saltasaurus had a relatively short neck with shortened neck vertebrae. The vertebrae from the middle part of its tail had elongated centra.[6] Saltasaurus had vertebral lateral fossae, pleurocoels, that resembled shallow depressions.[7] Fossae that similarly resemble shallow depressions are known from Malawisaurus, Alamosaurus, Aeolosaurus, and Gondwanatitan.[7] Venenosaurus also had depression-like fossae, but its pleurocoels penetrated deeper into the vertebrae, were divided into two chambers, and extend farther into the vertebral columns.[7] In Saltasaurus, the vertebral bone was generally cancellous and there were larger air chambers present as well. The limbs were short and stubby with especially short hands and feet. Saltasaurus had more robust radii than Venenosaurus.[8] The belly was extremely wide.

The osteoderms came in two types. There were larger oval plates with a length of up to twelve centimetres. These were keeled or spiked and perhaps were ordered in longitudinal rows along the back. The second type consists of small ossicles, rounded or pentagonal, about seven millimetres in diameter, that formed a continuous armour between the plates. A study in 2010 concluded that the larger plates had cancellous bone but that the ossicles had a denser bone tissue.[9]

Palaeobiology

Like all sauropods, Saltasaurus was herbivorous. Because of its barrel-like rump, shaped like a hippopotamus, Powell suggested that Saltasaurus was aquatic. Despite its small stature, Saltasaurus was still graviportal like other sauropods, meaning it could not run because its hindlimbs had to be held straight at the load-bearing phase of their walking cycle. Powell assumed adult individuals were protected against predators by their body armour, while juveniles were protected by the herd as a whole.[3]

In the Cretaceous Period, sauropods in North America were no longer the dominant group of herbivorous dinosaurs, with the ornithopod and ceratopsian dinosaurs, such as Edmontosaurus and Triceratops, becoming the most abundant (this being most evident by the Late Cretaceous epoch). However, on other landmasses such as South America and Africa (which were island continents much like modern Australia) sauropods, in particular the titanosaurs continued to be the dominant herbivores.

Saltasaurus was one such titanosaur sauropod, and lived around 70 million years ago. When it was first discovered, in 1975, it forced palaeontologists to reconsider some assumptions about sauropods as Saltasaurus possessed crocodile-like armour (osteoderms) 10 to 12 centimetres (4 to 5 in) in diameter. Previously, it had been assumed that size alone was sufficient defence for the massive sauropods. Since then, palaeontologists have investigated the possibility that other sauropods may also have had armour; for example, the Argentinian Laplatasaurus.

A new discovery, from another formation, may shed light on the nesting habits of Saltasaurus. A large titanosaurid nesting ground was discovered in Auca Mahuevo, in Patagonia, Argentina (another titanosaur nesting site has reportedly been discovered in Spain). Several hundred female saltasaurines 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 eggs, about 11–12 cm (4–5 in) in diameter, contained fossilised embryos, complete with skin impressions showing a mosaic armour of small bead-like scales. The armour pattern resembled that of Saltasaurus.[10]

Footnotes

  1. ^ J.F. Bonaparte, J.A. Salfity, G. Bossi & J.E. Powell, 1977, "Hallazgo de dinosaurios y aves cretacicas en la Formación Lecho de El Brete (Salta), proximo al limite con Tucumán", Acta Geològica Lilloana 14: 5-17
  2. ^ J.F. Bonaparte and J.E. Powell, 1980, "A continental assemblage of tetrapods from the Upper Cretaceous beds of El Brete, northwestern Argentina (Sauropoda-Coelurosauria-Carnosauria-Aves)," Mémoires de la Société Géologique de France, Nouvelle Série 139: 19-28
  3. ^ a b Powell, J.E., 1992, "Osteología de Saltasaurus loricatus (Sauropoda Titanosauridae) del Cretácico Superior del noroeste Argentino" In: Sanz, J., Buscalioni, A. (Eds.), Los dinosaurios y su entorno biótico: Actas del Segundo Curso de Paleontología in Cuenca, pp. 165-230
  4. ^ Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 213
  5. ^ Henderson, Donald (2013). "Sauropod Necks: Are They Really for Heat Loss?". PLoS ONE. 8 (10): e77108. Bibcode:2013PLoSO...877108H. doi:10.1371/journal.pone.0077108. PMC 3812985. PMID 24204747.
  6. ^ "Caudal Vertebrae," Tidwell, Carpenter, and Meyer (2001). Page 145.
  7. ^ a b c "Caudal Vertebrae," Tidwell, Carpenter, and Meyer (2001). Page 147.
  8. ^ "Forelimb," Tidwell, Carpenter, and Meyer (2001). Page 148.
  9. ^ Ignacio A. Cerda and Jaime E. Powell, 2010, "Dermal Armor Histology of Saltasaurus loricatus, an Upper Cretaceous Sauropod Dinosaur from Northwest Argentina", Acta Palaeontologica Polonica, 55(3): 389-398
  10. ^ Coria and Chiappe (2007).

References

Further reading

  • Walking on Eggs: The Astonishing Discovery of Thousands of Dinosaur Eggs in the Badlands of Patagonia, by Luis Chiappe and Lowell Dingus. June 19, 2001, Scribner. ISBN 0-7432-1211-8.

External links

Aeolosaurini

Aeolosaurini is an extinct clade of titanosaurian dinosaurs known from the late Cretaceous period of Argentina and Brazil. Thomas Holtz (2011) assigned Adamantisaurus, Aeolosaurus, Gondwanatitan, Muyelensaurus, Panamericansaurus, Pitekunsaurus and Rinconsaurus to Aeolosauridae. Rodrigo M. Santucci and Antonio C. de Arruda-Campos (2011) in their cladistic analysis found Aeolosaurus, Gondwanatitan, Maxakalisaurus, Panamericansaurus and Rinconsaurus to be aeolosaurids.

Camarasauridae

Camarasauridae (meaning "chambered lizards") is a family of neosauropod dinosaurs within the clade Macronaria, the sister group to Titanosauriformes. 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 jaw. Based on cervical vertebrae and cervical rib biomechanics, camarasaurids most likely moved their necks in a vertical, rather than horizontal, sweeping motion, in contrast to most diplodocids. Cladistically, they are defined to be all sauropods more closely related to Camarasaurus supremus than to Saltasaurus loricatus.

Dinosaur Planet (TV series)

Dinosaur Planet is a four-part American nature documentary that aired on the Discovery Channel as a special-two night event on December 14 and 16, 2003. It is hosted by paleontologist Scott Sampson and narrated by actor Christian Slater. It was released on DVD as a two-disc pack on February 17, 2004, and was also released on VHS around the same time.

The format is similar to Discovery's earlier series When Dinosaurs Roamed America. Each episode tells a fictionalized account of a dinosaur from the Late Cretaceous period. The animals are recreated with computer-generated imagery and composited into present-day filmed locations that approximate prehistoric Earth. Periodic interludes (three in each episode) feature Scott Sampson explaining the scientific findings behind the story, also similar to When Dinosaurs Roamed America, but has improved in quality.

Dinosaur classification

Dinosaur classification began in 1842 when Sir Richard Owen placed Iguanodon, Megalosaurus, and Hylaeosaurus in "a distinct tribe or suborder of Saurian Reptiles, for which I would propose the name of Dinosauria." In 1887 and 1888 Harry Seeley divided dinosaurs into the two orders Saurischia and Ornithischia, based on their hip structure. These divisions have proved remarkably enduring, even through several seismic changes in the taxonomy of dinosaurs.

The largest change was prompted by entomologist Willi Hennig's work in the 1950s, which evolved into modern cladistics. For specimens known only from fossils, the rigorous analysis of characters to determine evolutionary relationships between different groups of animals (clades) proved incredibly useful. When computer-based analysis using cladistics came into its own in the 1990s, paleontologists became among the first zoologists to almost wholeheartedly adopt the system. Progressive scrutiny and work upon dinosaurian interrelationships, with the aid of new discoveries that have shed light on previously uncertain relationships between taxa, have begun to yield a stabilizing classification since the mid-2000s. While cladistics is the predominant classificatory system among paleontology professionals, the Linnean system is still in use, especially in works intended for popular distribution.

Diplodocimorpha

Diplodocimorpha is a clade of extinct sauropod dinosaurs, existing from the Early Jurassic until the Late Cretaceous. The group includes three main families and some other genera, Rebbachisauridae, Dicraeosauridae and Diplodocidae, the latter two forming Flagellicaudata. The name was first used by Calvo & Salgado (1995), who defined it as "Rebbachisaurus tessonei sp. nov., Diplodocidae, and all descendants of their common ancestor." The group was not used often, and was synonymized with Diplodocoidea as the groups were often found to have the same content. In 2005, Mike P. Taylor and Darren Naish reviewed diplodocoid phylogeny and taxonomy, and realized that Diplodocimorpha could not be synonymized with Diplodocoidea. Whereas the former was defined node-based, the latter was branch-based. In 2015, Emanuel Tschopp, Octavio Mateus and Roger Benson published a specimen-based phylogeny on diplodocid interrelationships, and supported the separation of Diplodocimorpha. Haplocanthosaurus was found to be more basal than rebbachisaurids, and therefore outside Diplodocimorpha, but closer to Diplodocus than Saltasaurus, and therefore within Diplodocoidea. The below cladogram follows the findings of Tschopp et al.

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.

Maxakalisaurus

Maxakalisaurus is a genus of aeolosaurid dinosaur, found in the Adamantina Formation of Brazil, 45 kilometers (28 miles) from the city of Prata, in the state of Minas Gerais in 1998. It was related to Saltasaurus, a sauropod considered unusual because it had evolved apparently defensive traits, including bony plates on its skin and vertical plates along its spine; such osteoderms have also been found for Maxakalisaurus. The genus name is derived from the tribe of the Maxakali; Topa is one of their divinities.The type specimen of Maxakalisaurus belonged to an animal about 13 meters (43 feet) long, with an estimated weight of 9 tons, although, according to paleontologist Alexander Kellner, it could have reached a length of approximately 20 meters (66 feet). It had a long neck and tail, ridged teeth (unusual among sauropods) and lived about 80 million years ago. Because sauropods seem to have lacked significant competition in South America, they evolved there with greater diversity and more unusual traits than elsewhere in the world."This is the biggest dinosaur yet described in Brazil," said Alexander Kellner, lead author of the scientific description. "We have found the bones of what appear to be larger dinosaurs, but we still haven't been able to put them together for scientific descriptions."In 2016, a new specimen comprising a dentary and teeth was described as belonging to Maxakalisaurus. The phylogenetic analysis recovered Maxakalisaurus as an aeolosaurine along with Aeolosaurus and Gondwanatitan.A reconstructed Maxikalisaurus skeleton was on display in the National Museum of Brazil. It is currently unknown if it was damaged by the National Museum of Brazil fire on 2 September 2018.

Nemegtosauridae

Nemegtosauridae is a family of titanosaurian sauropod dinosaurs based originally on two late Cretaceous Mongolian species known only from their diplodocid-like skulls: Nemegtosaurus and Quaesitosaurus.

Nemegtosaurus

Nemegtosaurus (meaning 'Reptile from the Nemegt') was a sauropod dinosaur from Late Cretaceous Period of what is now Mongolia. Nemegtosaurus was named after the Nemegt Basin in the Gobi Desert, where the remains — a single skull — were found. The skull resembles diplodocoids in being long and low, with pencil-shaped teeth. However, recent work has shown that Nemegtosaurus is in fact a titanosaur, closely related to animals such as Saltasaurus, Alamosaurus and Rapetosaurus.

Neosauropoda

Neosauropoda is a clade within Dinosauria, coined in 1986 by Argentine paleontologist José Bonaparte and currently described as Saltasaurus loricatus, Diplodocus longus, and all animals directly descended from their most recent common ancestor. The group is composed of two subgroups: Diplodocoidea and Macronaria. Arising in the early Jurassic and persisting until the Cretaceous-Paleogene extinction event, Neosauropoda contains the majority of sauropod genera, including genera such as Apatosaurus, Brachiosaurus, and Diplodocus. It also includes giants such as Argentinosaurus, Patagotitan and Sauroposeidon, and its members remain the largest land animals ever to have lived.When Bonaparte first coined the term Neosauropoda in 1986, he described the clade as comprising “end-Jurassic” sauropods. While Neosauropoda does appear to have originated at the end of the Jurassic period, it also includes members through the end of the Cretaceous. Neosauropoda is currently delineated by specific shared, derived characteristics rather than the time period in which its members lived. The group was further refined by Upchurch, Sereno, and Wilson, who have identified thirteen synapomorphies shared among neosauropods. As Neosauropoda is a subgroup of Sauropoda, all members also display basic sauropod traits such as large size, long necks, and columnar legs.

Neuquensaurus

Neuquensaurus (meaning "Neuquén lizard") is a genus of saltasaurid sauropod dinosaur that lived in the Late Cretaceous, about 80 million years ago in Argentina and Uruguay in South America. Its fossils were recovered from outcrops of the Anacleto Formation around Cinco Saltos, near the Neuquén river from which its name is derived.

Rocasaurus

Rocasaurus (meaning "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 Maastrichtian in age (75 to 70 million years ago in the Late Cretaceous). This genus grew up to 8 metres (26 ft) long, making it one of the smaller sauropods. It seems to be closely related to saltasaurid dinosaurs, like Saltasaurus and Neuquensaurus.

The type species, Rocasaurus muniozi, was formally described by Leonardo Salgado and Azpilicueta in 2000.

Saltasauridae

Saltasauridae (named after the Salta region of Argentina where they were first found) — a family of armored herbivorous sauropods from the Upper Cretaceous. They are known from fossils found in South America, Asia, North America, and Europe. They are characterized by their vertebrae and feet, which are similar to those of Saltasaurus, the first of the group to be discovered and the source of the name. The last and largest of the group and only one found in North America, Alamosaurus, was thirty-four metres (112 feet) in length and the last sauropod to go extinct.

Most of the saltasaurids were smaller, around fifteen metres (49 feet) in length, and one, Rocasaurus, was only eight metres (26 feet) long. Like all sauropods, the saltasaurids were quadrupeds, their necks and tails were held almost parallel to the ground, and their small heads had only tiny, peg-like teeth. They were herbivorous, stripping leaves off of plants and digesting them in their enormous guts. Although large animals, they were smaller than other sauropods of their time, and many possessed distinctive additional defenses in the form of scutes along their backs.

Saltasaurinae

Saltasaurinae is a subfamily of titanosaurian sauropods known from the late Cretaceous period of South America, India and Madagascar. They are considered to be the most derived of all sauropods.

Somphospondyli

Somphospondylans are an extinct clade of titanosauriform sauropods that lived throughout the world from the Late Jurassic through the Cretaceous in North America, South America, Europe, Asia, Africa and Australia. The group can be defined as "the most inclusive clade that includes Saltasaurus loricatus but excludes Brachiosaurus altithorax". Features found as diagnostic of this clade by Mannion et al. (2013) include the possession of at least 15 cervical vertebrae; a bevelled radius bone end; sacral vertebrae with camellate internal texture; convex posterior articular surfaces of middle to posterior caudal vertebrae; biconvex distal caudal vertebrae; humerus anterolateral corner "squared"; among multiple others.

Titanosauria

Titanosaurs (members of the group Titanosauria) were a diverse group of sauropod dinosaurs which included Saltasaurus and Isisaurus of Africa, Asia, South America, Europe and Australia. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still thriving at the time of the extinction event at the end of the Cretaceous. The group includes the largest land animals known to have existed, such as Patagotitan—estimated at 37 m (121 ft) long with a weight of 69 tonnes (76 tons)—and the comparably sized Argentinosaurus and Puertasaurus from the same region. The group's name alludes to the mythological Titans of Ancient Greece, via the type genus (now considered a nomen dubium) Titanosaurus. Together with the brachiosaurids and relatives, titanosaurs make up the larger clade Titanosauriformes.

Zhuchengtitan

Zhuchengtitan (meaning "Zhucheng titan") is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous of Shandong, China. It contains a single species, Z. zangjiazhuangensis, named by Mo Jinyou and colleagues in 2017 from a single humerus. Zhuchengtitan can be identified by the extreme width of the top end of its humerus, as well as the expansion of the deltopectoral crest on its humerus; both of these characteristics indicate that it was likely closely related to Opisthocoelicaudia. However, it differs from the latter by the flatter bottom articulating surface of its humerus. Zhuchengtitan lived in a floodplain environment alongside Shantungosaurus, Zhuchengtyrannus, and Sinoceratops.

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