| Nemegtosaurids | |
|---|---|
 | |
| Cast of the skull ofNemegtosaurus, on a mountedOpisthocoelicaudia skeleton,Museum of Evolution of Polish Academy of Sciences,Warsaw | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Clade: | †Titanosauria |
| Clade: | †Eutitanosauria |
| Superfamily: | †Saltasauroidea |
| Family: | †Nemegtosauridae Upchurch, 1995 |
| Genera | |
Nemegtosauridae is afamily oftitanosauriansauropod dinosaurs based on theirdiplodocid-likeskulls.[1][2][3] Only three species are known:[4]Nemegtosaurus,Quaesitosaurus and possiblyTapuiasaurus, each from theCretaceous.
Due to the diplodocid-like nature of the taxa placed in Nemegtosauridae, the systematic position of this family in Sauropoda was disputed until recently. McIntosh (1990) included both these animals in the familyDiplodocidae, subfamilyDicraeosaurinae, as they resemble the skull ofDicraeosaurus, although differing in certain details. Although the skull ofNemegtosaurus was found in the same formation as the headless skeleton ofOpisthocoelicaudia, McIntosh (1990) keptNemegtosaurus in Diplodocoidea while keepingOpisthocoelicaudia separate from the former, a position reiterated by Upchurch (1995,[5] 1999[6]), and Upchurch et al. (2004). Acladistic analysis published in 2002 transferredNemegtosaurus andOpisthocoelicaudia fromDiplodocoidea toTitanosauria.[1]
Apesteguia (2004), in a paper describing a newPatagonian sauropod,Bonitasaura salgadoi, may have been the first to properly define the taxon, although without the use of cladistic analysis: the stemclade consisting of all titanosaurs more closely related toNemegtosaurus than toSaltasaurus. He argued for a close relationship betweenNemegtosaurus,Quaesitosaurus,Rapetosaurus, andBonitasaura and referred to the previous phylogenetic analysis and use of Nemegtosauridae by Wilson (2002).[7]
In his redescription of theNemegtosaurus holotype, Wilson (2005) elaborated on the titanosaurian nature ofNemegtosaurus, defining Nemegtosauridae as astem-based clade that includes all titanosaurs more closely related toNemegtosaurus than toSaltasaurus. He also suggested thatOpisthocoelicaudia may eventually be shown to be ajunior synonym ofNemegtosaurus.[8] For her part,Kristina Curry Rogers (see also Cuury Rogers and Forster [2001][9]) agreed with Wilson that bothNemegtosaurus andQuaesitosaurus were titanosaurs rather than diplodocoids, but rejected the validity of Nemegtosauridae and the clade concepts given under that name.Quaesitosaurus was placed in theSaltasaurinae andNemegtosaurus in a new, unnamed "Rapetosaurus clade" (which, under ICZN rules, would, if named, be termed subfamily Nemegtosaurinae or tribe Nemegtosaurini, depending on its position).Opisthocoelicaudia was placed in a separate clade, theOpisthocoelicaudiinae. All three clades are included in theSaltasauridae (= Titanosauridae).[10]
In a paper discussing new anatomical data on the skull ofTapuiasaurus, Wilson and his colleagues cast doubt on the monophyly of Nemegtosauridae, judging from a rescoring of the Zaher et al. 2011 cladistic analysis regarding cranial characters.Tapuiasaurus was recovered as basal to Lithostrotia, rendering its position within Nemegtosauridae questionable.[11] A 2014 cladistic analysis gleaning new anatomical data fromDiamantinasaurus also rendered Nemegtosauridae paraphyletic, withRapetosaurus falling out as a member of Saltasauridae closer toIsisaurus than toNemegtosaurus.[12] The cladistic analysis ofPatagotitan recoveredTapuiasaurus as the sister taxon ofRapetosaurus andIsisaurus but notNemegtosaurus.[13]
Nemegtosauridae was retained as a potentially useful clade of titanosaurs by Carballido and colleagues in 2022, who noted that it was either resolved as a small clade of titanosaurs, or an extensive group of taxa closer toNemegtosaurus thanSaltasaurus. Further work on the discovered postcrania was required to resolve the relationships ofNemegtosaurus andOpisthocoelicaudia, but it was preliminarily retained as a clade ofsaltasauroid that may end up as a synonym ofOpisthocoelicaudiinae or evenLirainosaurinae.[14]
Thecladogram below follows Zaheret al. (2011).[15]
| Lithostrotia | |
{{cite journal}}: CS1 maint: multiple names: authors list (link)
