Rinconsauria
A clade of small titanosaurs with highly unstable membership.
Rinconsauria is an extinct group of titanosaurian sauropods that lived during the late Cretaceous in what is now Argentina. Compared to the largest titanosaurs, all members of this clade were relatively small, measuring less than about 11 meters (36 feet) in length. Which dinosaurs belong to Rinconsauria is a matter of ongoing debate: some phylogenetic studies limit the group to just the two genera that define it—*Rinconsaurus* and *Muyelensaurus*—while other analyses have placed more than twenty additional titanosaur genera within the clade.
The clade was first named in 2007 by Calvo and colleagues to include *Muyelensaurus* and *Rinconsaurus*. Later work has produced conflicting results. For instance, Santucci and Arruda-Campos (2011), Franca et al. (2016), and Silva et al. (2019) all recovered Rinconsauria as part of Aeolosaurini. However, analyses by Gonzalez-Riga et al. (2019) and Mannion et al. (2019) placed *Aeolosaurus* in a different phylogenetic position, with Rinconsauria instead as the sister group to Lognkosauria within the larger clade Colossosauria. Not all studies even agree that *Muyelensaurus* and *Rinconsaurus* are close relatives: Santucci and Campos (2011) linked *Rinconsaurus* with *Aeolosaurus* while placing *Muyelensaurus* as a more basal titanosaur; Mannion et al. (2019) found *Rinconsaurus* to be a non-lithostrotian and *Muyelensaurus* a lithostrotian close to *Antarctosaurus* and *Mendozasaurus*; and Gallina and Otero (2015) found *Muyelensaurus* closer to a clade including *Futalognkosaurus*, *Mendozasaurus*, *Bonitasaura*, *Laplatasaurus*, and *Uberabatitan* than to *Rinconsaurus*. The relationship between Rinconsauria and Aeolosaurini is also unsettled: some analyses place Aeolosaurini within Rinconsauria, while others keep them separate.
A long list of genera have been included in Rinconsauria by various studies, but their membership is often inconsistent between analyses.
Quick Facts
- Taxon
- Rinconsauria
Facts from the source article.
Lore & Background
Rinconsauria was coined by Calvo et al. (2007) to include their new titanosaur Muyelensaurus and the previously described Rinconsaurus. Santucci and Arruda-Campos (2011) recovered Rinconsauria as part of Aeolosaurini, as did Franca et al. (2016) and Silva et al. (2019). However, cladistic analyses by Gonzalez-Riga et al. (2019) and Mannion et al. (2019) found Aeolosaurus to be in a phylogenetically disparate position than Rinconsauria, with Rinconsauria as sister to Lognkosauria in the clade Colossosauria.
The membership of Rinconsauria has varied considerably between different phylogenetic analyses. As originally proposed by Calvo and colleagues, the clade included only two genera, Rinconsaurus and Muyelensaurus, which were defined to be members of the clade. Not all phylogenetic analyses have recovered Muyelensaurus and Rinconsaurus as close relatives: Santucci and Campos (2011) linked Rinconsaurus with Aeolosaurus while placing Muyelensaurus as a more basal titanosaur; Mannion et al. (2019) found Muyelensaurus to be a non-lithostrotian and Rinconsaurus a lithostrotian close to Antarctosaurus and Mendozasaurus; and Gallina and Otero (2015) found Muyelensaurus closer to a clade including Futalognkosaurus, Mendozasaurus, Bonitasaura, Laplatasaurus, and Uberabatitan than to Rinconsaurus.
Reader's Guide
Rinconsauria represents a problematic but important clade within titanosaurian sauropods, primarily because its membership has been highly unstable across different phylogenetic analyses. Originally defined to include only Rinconsaurus and Muyelensaurus, over twenty other titanosaur genera have been placed within Rinconsauria by various studies, including Adamantisaurus, Aeolosaurus, Argyrosaurus, Arrudatitan, Baurutitan, Bonitasaura, Brasilotitan, Bravasaurus, Chadititan, Gondwanatitan, Maxakalisaurus, Narambuenatitan, Ninjatitan, Normanniasaurus, Overosaurus, Panamericansaurus, Pitekunsaurus, Punatitan, Rukwatitan, Shingopana, Trigonosaurus, and Uberabatitan. This instability reflects ongoing debates about titanosaur phylogeny, with some analyses placing Rinconsauria within Aeolosaurini and others separating them. The clade's significance lies in its potential to clarify evolutionary relationships among Cretaceous sauropods from South America, though consensus remains elusive. Its members are notable for being relatively small titanosaurs, all under 11 metres in length, contrasting with the gigantic sizes reached by other titanosaurs.
Did You Know?
- All members of Rinconsauria are less than around 11 metres (36 ft) long.
- Some analyses have found Rinconsauria to be sister to Lognkosauria within the clade Colossosauria.
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