Opisthocoelicaudiinae

Opisthocoelicaudiinae is a subfamily of titanosaurian dinosaurs from the Late Cretaceous. It was named by John McIntosh in 1990. Opisthocoelicaudiines are known from Mongolia, Argentina, and the United States. Two genera were assigned to Opisthocoelicaudiinae by Gonzalez et al. (2009): Alamosaurus and Opisthocoelicaudia (the type genus),^[5] a conclusion also found by Díez Díaz et al. (2018).^[1] The hands of opisthocoelicaudiines lacked wrist bones and phalanges.^[6]

Opisthocoelicaudiines Temporal range: Late Cretaceous, Maastrichtian PreꞒ Ꞓ O S D C P T J K Pg N
Opisthocoelicaudia skeleton restoration in Museum of Evolution of Polish Academy of Sciences in Warsaw
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Dinosauria
Clade:	Saurischia
Clade:	†Sauropodomorpha
Clade:	†Sauropoda
Clade:	†Macronaria
Clade:	†Titanosauria
Family:	†Saltasauridae
Subfamily:	†Opisthocoelicaudiinae McIntosh, 1990
Genera[1]
†Abditosaurus?[2] †Alamosaurus †Mansourasaurus?[3] †Nemegtosaurus?[4] †Opisthocoelicaudia †Pellegrinisaurus †Quaesitosaurus?[4] †Qunkasaura[2]
Synonyms
Opisthocoelicaudiidae (McIntosh, 1990) Averianiv & Lopatin, 2022 ?Nemegtosauridae Upchurch, 1995

It was suggested by Averianov and Lopatin in 2022 that Opisthocoelicaudia was not in fact closely related to Saltasaurus, and instead to Nemegtosaurus and Quaesitosaurus, which are both also Laurasian, as well as isolated teeth from the Turonian of Uzbekistan and the Santonian of Kazakhstan. Suggesting a more distant relationship to Saltasaurus, Averianiov and Lopatin suggested using the clade name Opisthocoelicaudiidae for the group, limiting Saltasauridae to Gondwanan taxa.^[4]

Opisthocoelicaudiinae in a cladogram after Navarro et al., 2022:^[7]

Saltasauridae	Opisthocoelicaudiinae Opisthocoelicaudia Nemegtosaurus Saltasaurinae Alamosaurus Baurutitan Ibirania Bonatitan Rocasaurus Saltasaurini Neuquensaurus MACN-PV-RN 233 Saltasaurus