Lithostrotia

In 1895, Richard Lydekker named the family Titanosauridae to summarize sauropods with procoelous (concave on the front) caudal vertebrae. 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. These authors consistently consider ranking groups that are based on Titanosaurus as the nominal taxon, Titanosauridae, Titanosaurinae and Titanosauroidea - also deemed 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. ==Definition and synapomorphies==

'' Upchurch and colleagues (2004) define the Lithostrotia as a node-based taxon which 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. ==Systematics==

Lithostrotia is a derived group of titanosaurs, excluding primitive forms such as Andesaurus and Phuwiangosaurus. 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. Another phylogenetic analysis by Poropat and colleagues in 2016, partially reproduced below, found Diamantinasaurus as a non-lithostrotian titanosaur and the sister taxon of the contemporary Savannasaurus. The cladogram below follows Mocho et al. (2019) with the new subgroup called Lirainosaurinae. 'Poropat et al. (2016)' }} 'Mocho et al. (2019)' }} While the clade Lithostrotia has been used in many different phylogenetic analyses as a description for a clade of titanosaurs, its use is not universal. The clade has been omitted from results as it has been considered a synonym of Titanosauria, or it has been used as either a very large clade encompassing almost all titanosaurs, or a smaller clade that excludes the taxa of Colossosauria. These incongruent results are because of the instability of the defining taxon Malawisaurus, which may in fact represent a chimaeric assemblage of remains and requires re-evaluation to determine what Lithostrotia includes. ==References==