A new genus and species of titanosaur has been identified from the fossilized remains found in the Hațeg Basin in Transylvania, western Romania.
An artist’s impression of a herd of lithostrotian dinosaurs (right). Image credit: ABelov / CC BY 3.0.
The newly-identified species lived on Hațeg Island, a large subtropical landmass in Tethys Ocean, some 70 million years ago (Cretaceous period).
Dubbed Uriash kadici, the animal belongs to Lithostrotia, a group of titanosaurian dinosaurs that includes many armored species.
“Titanosaurian sauropod dinosaurs include the largest animals to ever walk on land, with gigantic species that exceeded 60 tons,” said Dr. Verónica Díez Díaz, a paleontologist with the Museum für Naturkunde at the Leibniz-Institut für Evolutions- und Biodiversitätsforschung, and her colleagues.
“By the late Early Cretaceous, titanosaurs had achieved a near-global distribution, with their remains known from every landmass in the Late Cretaceous.”
“Despite a rich and global fossil record, titanosaurian evolutionary relationships are poorly known, limiting our understanding of this diverse clade of megaherbivores (the only group of sauropods to survive into the latest Cretaceous).”
“In particular, European titanosaurs have largely been neglected in phylogenetic analyses,” they said.
“This neglect mainly stems from the historical predominance of Gondwanan species, as well as the scarcity and incompleteness of Laurasian remains, especially from Europe.”
“However, this has begun to change through a combination of reassessments of existing species and specimens, as well as the discovery of new remains, including articulated, partial skeletons.”
“As such, the latest Cretaceous European sauropod fossil record, in particular, is starting to reveal a rich evolutionary history, with increasingly recognized importance for biogeographical scenarios and growing incorporation into phylogenetic analyses.”
The holotype of Uriash kadici was found in the Densuș-Ciula Formation of Hațeg Basin in Romania.
The dinosaur is estimated to have had a body mass of between 5 and 8 tons, and a body length close to 12 m.
“Uriash kadici is the largest titanosaurian species known from the Hațeg Basin, and surpassed the maximum values reached by most other Late Cretaceous European titanosaurs, with the exception of Abditosaurus (with estimates of 14 tons and 17.5 m in length),” the paleontologists said.
“The presence of large-sized titanosaurs such as Uriash kadici is noteworthy and requires explanation because it appears to contradict — or at least undermine — the supposed action of the ‘island rule’ upon these faunas.”
Uriash kadici co-existed with three other titanosaurian species: Magyarosaurus dacus, Paludititan nalatzensis and Petrustitan hungaricus.
According to the researchers, this diversity was likely even higher as evidenced by the substantial amount of associated fossils.
“Our phylogenetic analyses show that these Transylvanian titanosaurs present particularly close relationships with Gondwanan species: Magyarosaurus is recovered either as a member or a close relative of Saltasauridae; Paludititan has affinities with Lognkosauria, along with the approximately contemporaneous Spanish titanosaur Lohuecotitan; Petrustitan is most closely related to South American early diverging eutitanosaurian species; and Uriash shares one feature uniquely with Gondwanan titanosaurs,” they said.
“These analyses also strengthen the palaeobiogeographical hypothesis that the latest Cretaceous European titanosaurs were members of Gondwanan lineages that invaded the former area during the Barremian-Albian ages.”
“Since its initial discovery, Magyarosaurus dacus has been identified as a dwarfed sauropod, with island dwarfism proposed as an explanation for the diminutive size of this species and other dinosaurs on Hațeg Island.”
“Whereas Paludititan and Petrustitan are also small-bodied sauropods, Uriash was an order of magnitude heavier and represents one of the largest titanosaurian species found in the Late Cretaceous of Europe.”
“We interpret the presence of this body-size disparity as either evidence that large-bodied species were ecologically excluded from body-size reduction by competition from small-bodied titanosaurs, or that dwarfing occurred stratigraphically earlier among several lineages and the small-bodied titanosaurs on Hațeg Island are the descendants of existing dwarfed ancestors.”
“By contrast with some previous studies, we find no indication of a body-size related titanosaur turnover, involving replacement of dwarfed species with larger-sized ones, in the uppermost Cretaceous of the Transylvanian area.”
The discovery of Uriash kadici is reported in a paper published this month in the Journal of Systematic Palaeontology.
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Verónica Díez Díaz et al. 2025. Revision of Romanian sauropod dinosaurs reveals high titanosaur diversity and body-size disparity on the latest Cretaceous Haţeg Island, with implications for titanosaurian biogeography. Journal of Systematic Palaeontology 23 (1): 2441516; doi: 10.1080/14772019.2024.2441516
