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.[1] 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.

Saltasauridae
Temporal range: Late Cretaceous, 85.8–66 Ma
Saltasaurus dinosaur
Restoration of Saltasaurus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Sauropodomorpha
Clade: Sauropoda
Clade: Titanosauria
Clade: Lithostrotia
Family: Saltasauridae
Sereno, 1998
Genera
Synonyms
  • Balochisauridae Malkani, 2006

Description

As sauropods, the Saltasauridae are herbivorous saurischians with the characteristic body plan of a small head, long neck, four erect legs, and a counterbalancing tail. Most sauropods are from the clade Neosauropoda, which is further split into the narrow-toothed Diplodocoidea and the broad-toothed Macronaria. The Macronarians emerged in the Jurassic and a subclade, the Titanosauria, survived into the Cretaceous and spread across the continents. Because of their diversity, wide distribution, and the fragmentary or incomplete nature of most specimens, little is known about the titanosaurs beyond their size and tendency to have scutes.[2]

The saltasaurids, one of the several titanosaur families, are recognized by the convexities in certain caudal vertebrae and the markings on their coracoid bones.[3] All saltasaurids have thirty-five or fewer caudal vertebrae,[4] each of which is convex on both sides of its centrum, and the one closest to the tail is shorter than the others.[5] Their coracoid bones have rectangular margins on the anteroventral side, as well as a lip where they meet the infraglenoid. The Opisthocoelicaudiinae, a subfamily of the saltasaurids, are unique in that they lack phalanges in their forelimbs.[4][6] Although Saltasaurus is known to possess dorsal osteoderms, scutes have not been discovered in all saltasaurids, and it is unclear when and where the evolution of osteoderms occurred in saltasaurids and titanosaurs in general.[7]

History of study

The first saltasaurid to be discovered was Alamosaurus, found by paleontologist Charles Gilmore in Utah in 1922. The next species would not be described until Opisthocoelicaudia was named by Magdalena Borsuk-Bialynicka from a postcranial material in Mongolia in 1977. In 1980, Jose Bonaparte and Jaime Powell discovered Saltasaurus in Argentina. This was the first sauropod to be discovered with armor and proved that sauropods had thrived in Cretaceous South America. Paul Sereno eventually recognized a cladistic relationship between Opisthocoelicauda and Saltasaurus to create the family Saltasauridae.[8]

Classification

The group is defined by the characteristics shared by all with the two best-known members, Saltasaurus and Opisthocoelicaudia. Paleontologists J Wilson and P Upchurch defined the Saltasauridae in 2003 as the least inclusive clade containing Opisthocoelicaudia skarzynskii, and Saltasaurus loricatus, their most recent common ancestor, and all that species’ descendants.

Taxonomy

This taxonomy is based on those of González Riga et al. (2009) and Curry Rogers & Wilson (2005).[9][10]

Phylogeny

The family is then further divided into two subfamilies. Wilson and Upchurch defined Saltasaurinae in 2003 as the least-inclusive clade containing Saltasaurus but not Opisthocoelicaudia. The same paleontologists defined Opisthocoelicaudiinae as the inverse: the least-inclusive clade containing Opisthocoelicaudia but not Saltasaurus. Some species, due to the incompleteness of their skeletons, cannot yet be placed in either subfamily.

Paleobiology

Geographic range

Many fragmentary saltasaurids have been discovered since 1980, placing members of the family in territories as widely dispersed as today’s Australia, Madagascar, and France, in addition to their earlier-known residencies in North and South America. Like the other titanosaurs, the saltasaurids where a widespread, successful group that colonized all continents in the Cretaceous.[11]

Feeding habits

Like all titanosaurs, the saltasaurids possessed small, peg-like teeth that were not usable for chewing. Coproliths from an unidentified titanosaur found in India suggest a diet of conifers, cycads, and early species of grasses.[12] Unable to chew and probably lacking gastroliths, sauropods survived by retaining plant matter in their stomachs for long periods of time, fermenting it to extract as many resources as possible. Their long necks allowed them to graze over a large area while standing, reducing energy use.

Osteoderms

The osteoderms of Saltasaurus consisted of numerous, large bony plates embedded in the dorsal skin, each surrounded by a pattern of smaller plates. The large osteoderms contained some hollow spaces for blood vessels and spongy trabecular bone, while the small ones were solid.[13] Patches of skin from unidentified Cretaceous titanosaurs have revealed similar scale patterns in embryos (a large scale surrounded by ten smaller ones) but no bone or mineralized structure, suggesting that, like crocodiles, those saltasaurids that possessed armor only developed it some time after hatching. Analysis of the osteoderms of the titanosaur Rapetosaurus (not a member of Saltasauridae) revealed that the bones were hollow in adults, while those of juveniles were solid pieces similar to those in crocodiles. Paleontologist Kristina Curry Rogers, who made this discovery, theorized that the adult animals used their hollow osteoderms to store minerals during lean times. It is unknown whether any of the Saltasauridae used their osteoderms in a similar manner.[14]

Reproduction and development

The same Argentine dig site, Auca Mahuevo, that provided information on embryonic skin, has also yielded information on the nesting habits of titanosaurs, but not saltasaurids specifically. The nests were constructed on the surface by piling debris in a ring around the eggs, with the eggs themselves left uncovered. Each egg was porous and spherical, about 14 cm in diameter, and they were laid in clutches. The embryos show smaller rostrum and nares close to the anterior portion of the face compared to adult titanosaurs, suggesting that the nostrils may have moved towards the back of the head as the animal grew.[15]

References

  1. ^ Fastovsky, David; Weishampel, David; Sibbick, John (2009). Dinosaurs: a concise natural history. Cambridge: Cambridge University Press. Pg. 162-184.
  2. ^ Strauss, Bon (2016). Titanosaurs -- The Last of the Sauropods. About Education. Accessed May 17, 2016. <http://dinosaurs.about.com/od/typesofdinosaurs /a/titanosaurs.htm>
  3. ^ d'Emic, Michael D. (2012). "The early evolution of titanosauriform sauropod dinosaurs". Zoological Journal of the Linnean Society. 166 (3): 624–71. doi:10.1111/j.1096-3642.2012.00853.x.
  4. ^ a b Wilson, Jeffreya. (2002). "Sauropod dinosaur phylogeny: Critique and cladistic analysis". Zoological Journal of the Linnean Society. 136 (2): 215–75. doi:10.1046/j.1096-3642.2002.00029.x.
  5. ^ Wilson, Jeffrey A.; Martinez, Ricardo N.; Alcober, Oscar (1999). "Distal tail segment of a titanosaur (Dinosauria: Sauropoda) from the Upper Cretaceous of Mendoza, Argentina". Journal of Vertebrate Paleontology. 19 (3): 591–4. doi:10.1080/02724634.1999.10011168. JSTOR 4524019.
  6. ^ Tidwell, Virginia and Carpenter, Kenneth (2005). Thunder-Lizards: The Sauropodomorph Dinosaurs. Bloomington, Indiana: Indiana University Press. Pg. 339. ISBN 0-253-34542-1
  7. ^ Coria, Rodolfo A.; Chiappe, Luis M. (2007). "Embryonic Skin from Late Cretaceous Sauropods (Dinosauria) of Auca Mahuevo, Patagonia, Argentina". Journal of Paleontology. 81 (6): 1528–32. doi:10.1666/05-150.1. JSTOR 4541270.
  8. ^ P. C. Sereno. 1998. A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 210(1):41-83.
  9. ^ González Riga, Bernardo J.; Previtera, Elena; Pirrone, Cecilia A. (2009). "Malarguesaurus florenciae gen. Et sp. Nov., a new titanosauriform (Dinosauria, Sauropoda) from the Upper Cretaceous of Mendoza, Argentina". Cretaceous Research. 30 (1): 135–48. doi:10.1016/j.cretres.2008.06.006.
  10. ^ Curry Rogers, Kristina and Wilson, Jeffrey (2005). The Sauropods: Evolution and Paleobiology. University of California Press. Pg 38. https://books.google.com/books?id=X5j2lqAZqwIC&pg=PA346&lpg=PA346&dq=saltasauridae+phylogeny&source=bl&ots=FD57ZtLcW8&sig=UBzgi_EHIfChzDfxlGHdJHJgxbs&hl=en&sa=X&ved=0ahUKEwjajd7kqeDMAhXDFz4KHd6sC-QQ6AEILjAC#v=onepage&q=saltasauridae%20phylogeny&f=false
  11. ^ Prasad, V.; Strömberg, Caroline A. E.; Alimohammadian, Habib; Sahni, Ashok (2005). "Dinosaur Coprolites and the Early Evolution of Grasses and Grazers". Science. 310 (5751): 1177–80. Bibcode:2005Sci...310.1177P. doi:10.1126/science.1118806. PMID 16293759.
  12. ^ Cerda, Ignacio A.; Powell, Jaime E. (2010). "Dermal Armor Histology of Saltasaurus loricatus,an Upper Cretaceous Sauropod Dinosaur from Northwest Argentina". Acta Palaeontologica Polonica. 55 (3): 389–98. doi:10.4202/app.2009.1101.
  13. ^ Chiappe, Luis M.; Coria, Rodolfo A.; Dingus, Lowell; Jackson, Frankie; Chinsamy, Anusuya; Fox, Marilyn (1998). "Sauropod dinosaur embryos from the Late Cretaceous of Patagonia". Nature. 396 (6708): 258–61. Bibcode:1998Natur.396..258C. doi:10.1038/24370.
  14. ^ Curry Rogers, Kristina and Wislon, Jeffrey (2005). The Sauropods: Evolution and Paleobiology. University of California Press. Pg 293. https://books.google.com/books?hl=en&lr=&id=X5j2lqAZqwIC&oi=fnd&pg=PA285&dq=saltasaurus+nest&ots=FD57_vTdVc&sig=3QOW9yxhPufN7vgmDXJnwdv_Pd4#v=onepage&q=saltasaurus%20nest&f=false
  15. ^ Sander, P. Martin; Christian, Andreas; Clauss, Marcus; Fechner, Regina; Gee, Carole T.; Griebeler, Eva-Maria; Gunga, Hanns-Christian; Hummel, Jürgen; Mallison, Heinrich; Perry, Steven F.; Preuschoft, Holger; Rauhut, Oliver W. M.; Remes, Kristian; Tütken, Thomas; Wings, Oliver; Witzel, Ulrich (2011). "Biology of the sauropod dinosaurs: The evolution of gigantism". Biological Reviews. 86 (1): 117–55. doi:10.1111/j.1469-185X.2010.00137.x. PMC 3045712. PMID 21251189.
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.

Alamosaurus

Alamosaurus (; meaning "Ojo Alamo lizard") is a genus of titanosaurian sauropod dinosaurs, containing a single known species, Alamosaurus sanjuanensis, from the late Cretaceous Period of what is now southern North America. Isolated vertebrae and limb bones indicate that it reached sizes comparable to Argentinosaurus and Puertasaurus, which would make it the largest dinosaur known from North America. Its fossils have been recovered from a variety of rock formations spanning the Maastrichtian age of the late Cretaceous period. Specimens of a juvenile Alamosaurus sanjuanensis have been recovered from only a few meters below the Cretaceous-Paleogene boundary in Texas, making it among the last surviving non-avian dinosaur species.

Balochisaurus

Balochisaurus (meaning "Balochi lizard", for the Baloch tribes of Pakistan) is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous of Pakistan. The type species is B. malkani. The discovery was made (along with other dinosaur specimens) near Vitariki by a team of paleontologists from the Geological Survey of Pakistan. Formally described in 2006 by M.S. Malkani, the genus is based on seven tail vertebrae found in the Maastrichtian-age Vitakri Member of the Pab Formation, with additional vertebrae and a partial skull assigned to it. Balochisaurus was assigned to the family Balochisauridae along with Marisaurus, although the family was used as a synonym of older Saltasauridae.

Baotianmansaurus

Baotianmansaurus is a genus of titanosaur sauropod dinosaur. Its fossils have been found in Upper Cretaceous rocks in Henan, China, within the Gaogou Formation. The type species is B. henanensis, described in 2009. The holotype is 41H III-0200. Remains of the fossils were vertebrae, ribs and scapula fragments. It was probably a close relative of Opisthocoelicaudia and Dongyangosaurus in Saltasauridae.

Bonatitan

Bonatitan is a genus of titanosaurian dinosaur from the Late Cretaceous Allen Formation of Argentina.

Diamantinasaurus

Diamantinasaurus is an extinct genus of non-lithostrotian titanosaurian sauropod from Australia that lived during the early Late Cretaceous, about 94 million years ago. The type species of the genus is D. matildae, first described and named in 2009 by Scott Hocknull and colleagues. Meaning "Diamantina lizard", the name is derived from the location of the nearby Diamantina River and the Greek word sauros, "lizard". The specific epithet is from the Australian song Waltzing Matilda, also the locality of the holotype and paratype. The known skeleton includes most of the forelimb, shoulder girdle, pelvis, hindlimb and ribs of the holotype, and one shoulder bone, a radius and some vertebrae of the paratype.

Dongyangosaurus

Dongyangosaurus is a genus of saltasaurid sauropod dinosaur from the early Late Cretaceous. The only species is Dongyangosaurus sinensis, from which only a single fragmentary skeleton is known, coming from the Zhejiang province of eastern China. It was described and named by Lü Junchang and colleagues Like other sauropods, Dongyangosaurus would have been a large quadrupedal herbivore.

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.

Futalognkosaurus

Futalognkosaurus ( FOO-tə-long-ko-SAW-rəs; meaning "giant chief lizard") is a genus of titanosaurian dinosaur. The herbivorous Futalognkosaurus lived approximately 87 million years ago in the Portezuelo Formation, in what is now Argentina, of the Coniacian stage of the late Cretaceous Period. The fish and fossilized leaf debris on the site, together with other dinosaur remains, suggest a warm tropical climate in Patagonia during this period.

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.

Magyarosaurus

Magyarosaurus ("Magyar lizard") is a genus of dwarf sauropod dinosaur from late Cretaceous Period (early to late Maastrichtian) in Romania. It is one of the smallest-known adult sauropods, measuring only six meters in length. The type and only certain species is Magyarosaurus dacus. It has been found to be a close relative of Rapetosaurus in the family Saltasauridae in the sauropod clade Titanosauria in a 2005 study.

Marisaurus

Not to be confused with Merosaurus

Marisaurus (meaning "Mari lizard", for the Mari tribe of Pakistan) is a genus of titanosaurian sauropod from the Late Cretaceous of Balochistan, western Pakistan. The type species is M. jeffi, described by M. Sadiq Malkani in 2006, and it is based on tail vertebrae, found in the Maastrichtian-age Vitakri Member of the Pab Formation. Much additional material, including a partial skull, many vertebrae, and a few hindlimb bones, was referred to this genus. Marisaurus was assigned to Balochisauridae with Sulaimanisaurus, although the family was used as a synonym of Saltasauridae.

Microcoelus

Microcoelus is a dubius genus of small Titanosaurian sauropod dinosaur native to Argentina. It is known from only a single dorsal vertebra. A left humerus was formerly referred to this species, but it is now considered to belong to Neuquensaurus. This species may be a synonym of the contemporary sauropod Neuquensaurus australis.It was described by British paleontologist Richard Lydekker in 1893.

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.

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.

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.

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.

Volgatitan

Volgatitan is a genus of titanosaurian sauropod dinosaur from the Early Cretaceous of the Ulyanovsk Oblast, Russia. The type and only species is Volgatitan simbirskiensis, known from seven caudal vertebrae from a single individual. It is the oldest known titanosaur from the northern hemisphere, and is considered important for being related to the Lognkosauria, a group known only from South America later in the Late Cretaceous. It was first described in November 2018 by Russian palaeontologists Alexander Averianov and Vladimir Efimov.

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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