Eutitanosauria is a clade of

titanosaurs Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still th ...

, encompassing the more derived members of the group and characterized by the absence of the

hyposphene-hypantrum articulation The hyposphene-hypantrum articulation is an accessory joint found in the vertebrae of several fossil reptiles of the group Archosauromorpha. It consists of a process on the backside of the vertebrae, the hyposphene, that fits in a depression in the ...

and possibly the presence of

osteoderms Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct ...

. The group was first named by Sanz and colleagues in 1999, who used it to unite the group of '' Argyrosaurus'', ''

Lirainosaurus ''Lirainosaurus'' (meaning "slender lizard"; from the Basque ''lirain'', meaning "slender", and the Greek ''sauros'', meaning "lizard")is a genus of titanosaur sauropod which lived in what is now Spain. The type species, ''Lirainosaurus astibiae ...

'', ''

Saltasaurus ''Saltasaurus'' (which means "lizard from Salta") is a genus of saltasaurid dinosaur of the Late Cretaceous period of Argentina. Small among sauropods, though still heavy by the standards of modern creatures, ''Saltasaurus'' was characterized by ...

'' and the Peiropolis titanosaur. However, this definition was not used as it made the group equivalent to

Saltasauridae Saltasauridae (named after the Salta region of Argentina where they were first found) is a family of armored herbivorous sauropods from the Upper Cretaceous. They are known from fossils found in South America, Asia, North America, and Europe. Th ...

, so Saldago redefined it in 2003 to be all titanosaurs closer to ''Saltasaurus'' than ''

Epachthosaurus ''Epachthosaurus'' (meaning "heavy lizard") was a genus of titanosaurian sauropod dinosaur from the Late Cretaceous. It was a basal lithostrotian titanosaur. Its fossils have been found in Central and Northern Patagonia in South America. Discov ...

''. This definition created Eutitanosauria as the sister group to Epachthosaurinae (''Epachthosaurus'' but not ''Saltasaurus''), but was problematic due to the variable nature of ''Epachthosaurus''. Eutitanosauria was often broadly similar to Lithostrotia, and has often been unused or unlabelled on phylogenies. Sometimes ''Epachthosaurus'' would be more primitive than ''Malawisaurus'', making Eutitanosauria more encompassing than Lithostrotia, or ''Epachthosaurus'' could nest close to Colossosauria and limit Eutitanosauria to a smaller group of saltasauroids. Because of the flexible nature of ''Epachthosaurus'' in basal titanosaur phylogeny, Carballido and colleagues redefined the group in 2022 to include the smallest clade of both ''

Patagotitan ''Patagotitan'' is a genus of titanosaurian sauropod dinosaur from the Cerro Barcino Formation in Chubut Province, Patagonia, Argentina. The genus contains a single species known from multiple individuals: ''Patagotitan mayorum'', first announc ...

'', a colossosaur, and ''Saltasaurus'', creating a node-stem clade with Colossosauria and Saltasauroidea, presenting the informal cladogram of stable titanosaur clades below.

References

{{Taxonbar, from=Q515777 Titanosaurs Late Cretaceous dinosaurs