The lithostrotian titanosaur Magyarosaurus has long been significant for demonstrating the presence of dwarf titanosaurs in the latest Cretaceous of Europe, but until recently an up-to-date re-appraisal of the titanosaur material referred to Magyarosaurus in the past was lacking, although the description of the similarly dwarf-sized Paludititan by Csiki et al. (2010) signaled that more than one taxon of titanosaur existed in the Late Cretaceous of Romania. Now, Diez Diaz et al. (2025) have come out with the long-overdue revision of nominal titanosaur taxa assigned to Magyarosaurus from the latest Cretaceous of Transylvania, confirming suspicions about more than one genus being represented in the material referred to Magyarosaurus by von Huene (1932).
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| Lectotype and paralectotype of Petrustitan hungaricus (NHMUK R.3853) (from Diez Diaz et al. 2025) |
As a prelude to the "Systematic palaeontology" section of their paper, Diez Diaz et al. provide a relatively short overview of a number of publications making the case for the existence of more than one titanosaur species in Transylvania, including Stein et al. (2010) and the paper by Csiki et al. (2010) describing the new titanosaur taxon Paludititan nalatzensis. They note that McIntosh (1990) found it conceivable that more than one taxon is represented in the titanosaur material assigned by von Huene (1932) to Magyarosaurus, and the paper by Mocho et al. (2023) identifying four distinct titanosaur caudal morphotypes from the Hațeg Island region provides the authors with an impetus to clarify the taxonomy of Transylvanian titanosaurs based on overlap and shared characters between type specimens and referred material for Magyarosaurus dacus, M. hungaricus, and M. transsylvanicus.
The assortment by Diez Diaz et al. of name-bearing and "Rosetta Stone" Transylvanian titanosaur specimens into "individuals" and "assemblages" in quite creative. The authors rely on locality data for these specimens and specimen preservation and registry notes when labeling the type material of Magyarosaurus dacus as an assemblage and the type remains of Petrustitan hungaricus as an individual while referring to a number of non-type specimens from select localities with duplicate elements as assemblages. This is important because the type material of P. hungaricus comprises only a left fibula and tibia, the former which nevertheless allowed for Diez Diaz et al. (2025) to compare NHMUK R.3853 to Magyarosaurus dacus by overlapping with the fibulae included in type material for M. dacus. Paradoxically, Diez Diaz et al. neglect to designate one of the fibulae included in the hypodigm for Magyarosaurus transsylvanicus by von Huene (1932) as the lectotype of transsylvanicus even though they demonstrate that the hypodigm for this species is a composite of Magyarosaurus and indeterminate titanosaur remains, with the fibulae belonging to M. dacus and the vertebrae and forelimb remains being indeterminate beyond Titanosauria.
The phylogenetic analysis of Transylvanian titanosaurs by Diez Diaz et al. (2025) is quite breathtaking. Although Cury Rogers (2005) recovered Magyarosaurus as a lithostrotian titanosaur, her cladistic analysis found that taxon to be of uncertain placement within Lithostrotia. Given that Magyarosaurus is a dwarf taxon, its placement within Saltasauridae by Diez Diaz et al. indicates that Magyarosaurus itself arose from African saltasaurids that evolved insular dwarfism after colonizing island chains in southern Europe. The authors' recovery of Paludititan as closely related to or within Lognkosauria differs from the placement of Paludititan as a member of Lirainosaurinae in the phylogeny by Mocho et al. (2024), On the other hand, Nemegtosaurus falls outside Saltasauridae in the cladistic analysis by Diez Diaz et al. (2025), while the equal weights analysis finds Malawisaurus to be sister to a clade composed of Andesaurus, Baotianmansaurus, Daxiatitan, Dongyangosaurus, Huabeisaurus, and Xianshanosaurus. The placement of Nemegtosaurus outside Saltasauridae is most likely a fluke because it is coeval with Opisthocoelicauda, but the Diez Diaz et al. cladistic analysis is in lockstep with the phylogeny in Han et al. in placing Huabeisaurus as a late-surviving basal titanosaur. The recovery of Petrustitan as sister to Antarctosaurus, Vahiny, and Jainosaurus could attest to Antarctosaurus-like titanosaurs evolving insular dwarfism after entering Europe from North Africa because Diez Diaz et al. (2025) assess Petrustitan as a dwarf titanosaur.
In summary, the paper by Diez Diaz et al. (2025) is kind of a magnum opus with respect to the alpha-taxonomy of Transylvania's titanosaur fauna because it re-evaluates all nominal referred species of Magyarosaurus in light of the description of Paludititan over a decade ago. Moreover, the authors of this paper demonstrate that the titanosaur fauna from Hațeg Island comprises both insular dwarfs and large-bodied forms judging from the large size of the newly described taxon Uriash. By refining the cladistic position of the Transylvanian titanosaurs, this paper will be useful for future discussions of the biogeography of derived titanosaurs as they relative to the inter-relationships of lithostrotians.
References:
Curry Rogers, K. A., 2005. Titanosauria: A Phylogenetic Overview. pp. 50-103. In: Curry Rogers and Wilson (eds), The Sauropods: Evolution and Paleobiology. University of California Press: Berkeley.
Codrea, V., Jipa-Murzea, C., and Godefroit, P., 2010. A partial titanosaur (Sauropoda, Dinosauria) skeleton from the Maastrichtian of Nǎlaţ-Vad, Haţeg Basin, Romania. Neues Jahrbuch fur Geologie und Palaontologie – Abhandlungen 258 (3), 297–324.
Díez Díaz, V., Mannion, P.D., Csiki-Sava, Z., and Upchurch, P., 2025. Revision of Romanian sauropod dinosaurs reveals high titanosaur diversity and body-size disparity on the latest Cretaceous Hațeg Island Island, with implications for titanosaurian biogeography. Journal of Systematic Palaeontology 23 (1): 2441516. doi:10.1080/14772019.2024.2441516
Han, F., Yang, L., Lou, F., Sullivan, C., Xu, X., Qiu, W., Liu, H., Yu, J., Wu, R., Ke, Y., Xu, M., Hu, J., and Lu, P., 2024. A new titanosaurian sauropod, Gandititan cavocaudatus gen. et sp. nov., from the Late Cretaceous of southern China. Journal of Systematic Palaeontology 22 (1): 2293038. doi: https://doi.org/10.1080/14772019.2023.2293038.
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