The description of the derived titanosaur Abditosaurus by Viel et al. (2022) upended the long-standing view that all titanosaur taxa described from the Campanian-Maastrichtian of the Ibero-Armorican island (now northeastern Spain and southern France) were dwarf, insular forms because known specimens of Abditosaurus kuehnei are larger than Ampelosaurus, Lirainosaurus, Magyarosaurus, and other dwarf titanosaurs from the Late Cretaceous of Europe. Now, Mocho et al. (2024) have described yet another non-dwarf titanosaur from the Late Cretacrous of Spain, Qunkasaura pintiquiniestra, which hails from the type locality of the co-eval titanosaur Lohuecotitan pandafilandi in Lo Hueco, south-central Spain. While Qunkasaura constitutes the newest addition to an already-burgeoning inventory of lithostrotian titanosaurs from the Ibero-Armorican realm, there are aspects of the phylogenetic analysis of this taxon by Mocho et al. (2024) that are quite novel and worth discussing.
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| Phylogenetic analysis of Qunkasaura pintiquiniestra by Mocho et al. (2024) showing bifurcation of Saltasauroidea into Lohuecosauria and a Rapetosaurus+Overosaurus clade. |
The most tangible taxonomic action concocted by Mocho et al. as a result of their cladistic analysis of Qunkasaura involves a shake-up of the phylogenetic nomenclature for and interrelationships of taxa outside South America assigned to Saltasauridae. The creation of the new name Lohuecosauria for a clade within Saltasauroidea comprising Lirainosaurinae, Saltasauridae, and Isisaurus by the authors constitutes a bold effort to tackle the interrelationships of Saltasaurus-like lithostrotians because the cladistic analysis by Mocho et al. (2024) differs from the phylogeny of Diez Díaz et al. (2018) in recovering Lirainosaurinae as closely related to Saltasauridae rather than as sister to Lognkosauria, suggesting that lirainosaurines may have evolved in Gondwana prior to the Maastrichtian and became the dominant titanosaur clade in Europe by the Maastrichtian. In particular, Carballido et al. (2022) noted that the Sallam et al. (2018) phylogeny recovering Opisthocoelicauda within Lirainosaurinae (which would have meant Opisthocoelicaudiinae having priority over Lirainosaurinae) in contrast to the results by Diez Díaz et al. rendered the exact cladistic position of Lirainosaurinae, and by finding Lirainosaurinae to be basal to Isisaurus and Saltasauridae, Mocho et al. do an outstanding job of tackling the question of whether Opisthocoelicaudia is closely related to members of Lirainosaurinae, because the saltasaurid Ibirania described from the late Santonian-early Campanian of southeastern Brazil by Navarro et al. (2022) is a dwarf taxon like many members of Lirainosaurinae, implying that the dwarfism evolved independently within different clades of Lohuecosauria during the Santonian-Maastrichtian interval.
The recovery of Nemegtosaurus as closely related to Lognkosauria by Mocho et al. (2024) is quite remarkable. Diez Díaz et al. (2018) and Sallam et al. (2018) also find Nemegtosaurus to be the sister taxon of Rinconsaurus, Muyelensaurus, Lognkosauria, Aeolosaurus, and Gondwanatitan, but the placement of Nemegtosaurus within Colossosauria as closely related to Lognkosauria should be taken with a grain of salt because of marginal overlap between the few postcranial elements assigned to the holotype of N. mongoliensis from the type locality of this taxon by Currie et al. (2018) and postcranial remains of lognkosaurian taxa but also the younger age of Nemegtosaurus compared to lognkosaurian taxa included in the phylogeny by Mocho et al. except Garrigatitan and Puertasaurus. Still, Mocho et al. (2024) agree with Wilson et al. (2016) and Navarro (2019) that Rapetosaurus does not group with Nemegtosaurus to the exclusion of other derived lithostrotians, especially as their cladistic analysis finds Rapetosaurus and Tapuiasaurus to be distantly related despite overlap between known skeletal elements for those taxa. As a matter of fact, cladistic analyses by Navarro et al. (2022) and Gorcsak et al. (2023) recover Nemegtosaurus and Opisthocoelicaudia within Saltasauridae, which makes sense when considering that few postcranial elements are known for Nemegtosaurus despite overlap with those of Opisthocoelicaudia.
Mocho et al.'s note of caution on the cladistic positions of Garrigatitan and Normanniasaurus as well the Algora titanosaur within Colossosauria is quite reasonable. While I agree that newly discovered titanosaur material from Cenomanian-age deposits in Algora, Spain may shift the cladistic position of the Algora taxon to a different spot within Lithostrotia, the placement of Normanniasaurus within Colossosauria could still stand because a number of topologies in Mannion et al. (2019) happen to recover Normanniasaurus as sister to Lognkosauria and Aeolosaurus despite the incompleteness of the N. genceyi holotype. Although Mocho et al. (2024) call into question the tentative referral of some specimens to Garrigatitan, making their cladistic recovery of Garrigatitan as a lognkosaurian tenuous, Garrigatitan could still be a member of Colossosauria despite being based on incomplete material because the cladistic results in Mocho et al. (2024) demonstrate the co-existence of two distinct clades of saltasauroids in the Campanian-Maastrichtian of Europe.
References:
Carballido, J.L., Otero, A., Mannion, P.D., Salgado, L., and Moreno, A.P., 2022. Titanosauria: A Critical Reappraisal of Its Systematics and the Relevance of the South American Record. pp. 269-298. In Otero, A.; Carballido, J.L.; Pol, D. (eds.). South American Sauropodomorph Dinosaurs. Record, Diversity and Evolution. Cham, Switzerland: Springer. doi:10.1007/978-3-030-95959-3.
Currie, P. J., Wilson, J.A., Fanti, F., Mainbayar, B., and Tsogtbaatar, K., 2018. Rediscovery of the type localities of the Late Cretaceous Mongolian sauropods Nemegtosaurus mongoliensis and Opisthocoelicaudia skarzynskii: Stratigraphic and taxonomic implications. Palaeogeography, Palaeoclimatology, Palaeoecology 494:5–13. doi:10.1016/j.palaeo.2017.10.035.
Díez Díaz, V., Garcia, G., Pereda-Suberbiola, X., Jentgen-Ceschino, B., Stein, K., Godefroit, P., and Valentin, X., 2018. The titanosaurian dinosaur Atsinganosaurus velauciensis (Sauropoda) from the Upper Cretaceous of southern France: New material, phylogenetic affinities, and palaeobiogeographical implications. Cretaceous Research. 91: 429–456. doi:10.1016/j.cretres.2018.06.015
Gorscak, E., Lamanna, M. C., Schwarz, D., Díez Díaz, V., Salem, B. S., Sallam, H. M., and Wiechmann, M. F., 2023. A new titanosaurian (Dinosauria: Sauropoda) from the Upper Cretaceous (Campanian) Quseir Formation of the Kharga Oasis, Egypt. Journal of Vertebrate Paleontology e2199810. doi:10.1080/02724634.2023.2199810.
Mocho, P., Escaso, F., Marcos-Fernández, F., Páramo, A., Sanz, J. L., Vidal, D., and Ortega, F., 2024. A Spanish saltasauroid titanosaur reveals Europe as a melting pot of endemic and immigrant sauropods in the Late Cretaceous. Communications Biology 7: 1016. doi:10.1038/s42003-024-06653-0
Navarro, B.A., Ghilardi, A.M., Aureliano, T., Díaz, V.D., Bandeira, K.L. N., Cattaruzzi, A.G.S., Iori, F.V., Martine, A.M., Carvalho, A.B., Anelli, L.E., Fernandes, M.A., and Zaher, H., 2022. A new nanoid titanosaur (Dinosauria: Sauropoda) from the Upper Cretaceous of Brazil. Ameghiniana 59(5): 317–354. doi:10.5710/AMGH.25.08.2022.3477
Sallam, H., Gorscak, E., O'Connor, P., El-Dawoudi, I., El-Sayed, S., and Saber, S., 2018. New Egyptian sauropod reveals Late Cretaceous dinosaur dispersal between Europe and Africa. Nature 2 (3): 445–451.
Vila, B., Sellés, A., Moreno-Azanza, M., Razzolini, N.L., Gil-Delgado, A., Canudo, J.I., and Galobart, A., 2022. A titanosaurian sauropod with Gondwanan affinities in the latest Cretaceous of Europe. Nature Ecology & Evolution 6: 288-296. doi:10.1038/s41559-021-01651-5.
Wilson, J. A., D. Pol, A. B. Carvalho, and H. Zaher. 2016. The skull of the titanosaur Tapuiasaurus macedoi (Dinosauria: Sauropoda), a basal titanosaur from the Lower Cretaceous of Brazil. Zoological Journal of the Linnean Society 178(3):611–662.
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