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.
|Life restorations of a pair of Saltasaurus|
Upchurch et al., 2004
In 1895, Richard Lydekker named the family Titanosauridae to summarize sauropods with procoelous (concave on the front) caudal vertebrae. The name Titanosauridae has since been widely used, and was defined by Salgado and colleagues (1997), Gonzalaz-Riga (2003) and Salgado (2003) as node-based taxon. According to a proposal by Wilson and Upchurch (2003) looks today much of the research on the use of that name from: Wilson and Upchurch published a revision of the genus Titanosaurus and declare the type species Titanosaurus indicus as invalid because it is based only on two vertebrae of the tail, showing no diagnostically usable features. Consistently these authors consider ranking groups that are based on Titanosaurus as the nominal taxon, Titanosauridae, Titanosaurinae and Titanosauroidea - also considered invalid. In 2004 Upchurch and colleagues presented the new group Lithostrotia to describe the same group as Titanosauridae, but instead it was not based upon a specific taxon. The name Lithostrotia is not currently recognized by all researchers.
Upchurch and colleagues (2004) define the Lithostrotia as a node-based taxon that includes the last common ancestor of Malawisaurus and Saltasaurus and all descendants of that ancestor. According to this definition the Lithostrotia includes all forms that are more derived than Malawisaurus in phylogenies.
In addition to defining the group Upchurch and colleagues gave two common derived features (synapomorphies), which serve to distinguish the group from non-members. The first is that all caudal vertebrae apart from the farthest distal were procoelous, meaning their front face was concave. Also, the front (proximal) caudal vertebrae were particularly strong procoelous. This first feature is also shared with Mamenchisauridae.
Unchurch et al. named Lithostrotia based on the presence of osteoderms in many members, but the eponymous osteoderms do not represent synapomorphy, as the evolutionary history of osteoderms is unknown within the titanosaurs. It may be this trait has developed multiple times independently within the titanosaurs and Lithostrotia, as osteoderms are known in many saltasaurids, Mendozasaurus, Aeolosaurus, Ampelosaurus and various other genera both within and outside Lithostrotia with different morphologies.
Lithostrotia is a derived group of titanosaurs, excluding primitive forms such as Andesaurus and Phuwiangosaurus. The possibly equivalent clade Titanosauridae was positioned in a phylogenetic analysis by Calvo et al. (2007), where it included all titanosaurs apart from Andesaurus, though multiple primitive forms were not analyzed. Other phylogenies, by Unchurch et al. (2015), instead have found a few, non-lithostrotian titanosaurs, or nearly all non-brachiosaurid titanosauriformes within the group. Poropat et al. (2015) conducted a similar analysis to one of Unchurch et al. (2015). This analysis found that Andesaurus, Argentinosaurus and Epachthosaurus were within Titanosauria but outside Lithostrotia, and the latter group included Malawisaurus, Nemegtosaurus, Diamantinasaurus, Tapuiasaurus and Alamosaurus as basal lithostrotians outside Saltasauridae. The results of their analysis is shown below.
Adamantisaurus ( AD-ə-man-ti-SAWR-əs) is a poorly-known genus of titanosaurian sauropod dinosaur from the Late Cretaceous Period of what is now South America. It is only known from six tail vertebrae but, as a sauropod, it can be assumed that this dinosaur was a very large animal with a long neck and tail.
Like many titanosaurians, Adamantisaurus is incompletely known, making its exact relationships difficult to establish. However, similarities have been noted with Aeolosaurus and the Bauru Group titanosaurian formerly known as the "Peiropolis titanosaur", now called Trigonosaurus.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.Austroposeidon
Austroposeidon is an extinct genus of titanosaurian sauropod dinosaur from the Late Cretaceous Presidente Prudente Formation of Brazil. It contains one species, Austroposeidon magnificus.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.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.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.Gondwanatitan
Gondwanatitan (meaning "giant from Gondwana") was a titanosaurian sauropod dinosaur. Gondwanatitan was found in Brazil, at the time part of the southern supercontinent Gondwana, in the late Cretaceous Period (70 mya). Like some other sauropods, Gondwanatitan was tall and ate tough shoots and leaves off of the tops of trees. G. faustoi's closest relative was Aeolosaurus.
The type species is Gondwanatitan faustoi, formally described by Kellner and de Azevedo in 1999.Jiangshanosaurus
Jiangshanosaurus was a titanosaurian sauropod that lived approximately 105 million years ago, during the Albian stage of the Early Cretaceous. Its remains were discovered in the Jinhua Formation of Lixian Village, Jiangshan county, in the eastern Chinese province of Zhejiang. The type and only known species, Jiangshanosaurus lixianensis, was formally described by Tang Feng and others in 2001. Known material of J. lixianensis includes elements of the shoulder, back, pelvis, femur and tail. Although Jiangshanosaurus initially defied precise placement within Titanosaura, a recent paper considers it to be outside Lithostrotia.Lognkosauria
Lognkosauria is a group of giant long-necked sauropod dinosaurs within the clade Titanosauria. It includes some of the largest and heaviest dinosaurs known.Lohuecotitan
Lohuecotitan is an extinct genus of titanosaurian sauropod dinosaur which lived during the Late Cretaceous in Spain. The only species known in the genus is Lohuecotitan pandafilandi, described and named in 2016.Narambuenatitan
Narambuenatitan is a genus of lithostrotian titanosaur sauropod from late Cretaceous (lower-middle Campanian stage) deposits of northern Patagonia of Argentina. Narambuenatitan is known from the holotype MAU-Pv-N-425, an incomplete skeleton. It was collected in 2005 and 2006 from the Anacleto Formation (Neuquén Group) in northern Patagonia. It was first named by Leonardo S. Filippi, Rodolfo A. García and Alberto C. Garrido in 2011 and the type species Narambuenatitan palomoi. The generic name refers to Puesto Narambuena. The specific name honours the discoverer, Salvador Palomo.Narmabuenatitan was assigned to the clade Lithostrotia in a trichotomy with Epachthosaurus and the more derived clade Eutitanosauria.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.Notocolossus
Notocolossus is a genus of herbivorous lithostrotian titanosaur sauropod dinosaur from late Cretaceous strata of Mendoza Province, Argentina.Overosaurus
Overosaurus is an extinct genus of sauropod dinosaurs, containing only a single species, Overosaurus paradasorum. This species lived approximately 84 to 78 million years ago during the latter part of the Cretaceous Period in what is now Patagonia (in southern Argentina). Overosaurus paradasorum was relatively small compared to other sauropods from Patagonia, like the saltasaurids and other aeolosaurines. It was a ground-dwelling herbivore, that could grow up to 8.6 m (28.2 ft) long.Ruyangosaurus
Ruyangosaurus (Ruyang County lizard) is a genus of titanosauriform sauropod dinosaur recovered from the Early Cretaceous Haoling Formation of China. The type species is R. giganteus, described in 2009 by Lü Junchang et al. Along with Huanghetitan and Daxiatitan, Ruyangosaurus is among the largest dinosaurs discovered in Cretaceous Asia.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.Tengrisaurus
Tengrisaurus (meaning "Tengri lizard") is a genus of lithostrotian sauropod, from the Early Cretaceous (Barremian-Aptian), of the Murtoi Formation, Russia. It was described in 2017 by Averianov & Skutschas. The type species is T. starkovi.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.