Udelartitan

MEANING: "Universidad de la República" giant

PERIOD: Late Cretaceous

CONTINENT: South America

Udelartitan had the typical sauropod body plan, standing on four thick pillar-like legs, and possessing a long neck. Titanosaurs are a very diverse group, and Udelartitan was a small one, estimated at only 15 m in body length. Though a skull has yet to be discovered, it probably had peglike teeth, and a large gut for processing vegetation.

Abstract from paper: The up to 200 m thick Upper Cretaceous deposits of Uruguay includes from base to top the Guichón, Mercedes, and Asencio formations, plus the lateral correlate of the latter, the Queguay Formation. In 2006, the most complete sauropod from the country was excavated from the Guichón Formation near Araújo, Paysandú Department. Augmented by new specimens reported here, the material includes sixty caudal vertebrae (all strongly procoelous, except for the biconvex first one), a partial coracoid, long bone fragments (proximal and distal portions of tibia, proximal portion of fibula), two astragali, and six metatarsals, as well as associated eggshell fragments. The Uruguayan titanosaur shows a unique combination of characters (biconvex first caudal centrum, pneumatic foramina in the anteriormost caudal centra, dorsal tuberosities on the transverse processes of the anterior caudal vertebrae, well developed fibular knob, pyramidal astragalus), as well as a potential autapomorphy – middle caudal centra condyles with hexagonal contour – allowing the proposition of new genus and species, Udelartitan celeste. Phylogenetic analyses were for the first time performed to assess the relations of that taxon, which was recovered either as a saltasaurine saltasaurid or a non-saltasaurid saltasauroid. Further, one of the analyses show Udelartitan celeste nested within a clade including Late Cretaceous titanosaurs with a biconvex first caudal vertebra, such as Alamosaurus sanjuanensis, Baurutitan britoi, and Pellegrinisaurus powelli. This contribution demonstrates that at least two titanosaur lineages were present in the Late Cretaceous of Uruguay: Saltasauroidea and Aeolosaurini, the latter recently recognized in the stratigraphically younger Asencio Formation.

Udelartitan is from the Late Cretaceous. The Cretaceous is the third and final geological period of the Mesozoic Era, with the Late Cretaceous making up roughly the second half of it, lasting from about 100 to 66 million years ago. It was a time of significant evolutionary change, with dinosaurs reaching their greatest diversity before the mass extinction at the end of the Cretaceous.

The Cretaceous was a period with a relatively warm climate, though the Late Cretaceous experienced a global cooling trend, caused by falling levels of carbon dioxide in the atmosphere. The continents were nearing their present positions, but high sea levels flooded low-lying regions, turning Europe into an archipelago, and forming the Western Interior Seaway in North America. These seas were home to a variety of marine reptiles, including mosasaurs and plesiosaurs, while pterosaurs and birds shared the skies.

On land, dinosaurs continued to thrive and diversify during the Late Cretaceous, producing many of the most well-known groups, including tyrannosaurs, hadrosaurs, and pachycephalosaurs. Established Cretaceous dinosaur clades like the ceratopsians, ankylosaurs, and dromaeosaurs continued to flourish. Sauropod species consisted almost exclusively of titanosaurs, which seemed to be confined to the Southern Hemisphere for much of the Late Cretaceous. Flowering plants and grasses diversified and spread, becoming the dominant flora similar to what we see today.

The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene (K–Pg) extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. This event, likely triggered by an asteroid impact, is marked by the abrupt K–Pg boundary, a distinct geologic layer separating the Mesozoic and Cenozoic Eras. In its aftermath, mammals and avian dinosaurs rapidly diversified, becoming the dominant land animals of the Cenozoic Era.

Udelartitan is a titanosaur. Titanosauria was a diverse and widespread group of sauropod dinosaurs that lived during the Cretaceous Period, especially flourishing in the Late Cretaceous. As the final major lineage of sauropods, they replaced older groups like the diplodocids and brachiosaurids. Sauropods are herbivorous saurischian dinosaurs known for their long necks and immense size, and titanosaurs took this to the greatest extreme. Estimates vary, but the largest titanosaurs are estimated at upward of around 40 m long, and weighing 100 t in total body mass, or possibly even more. While this derived group included the largest animals ever to walk the earth, it is also notable for its diversity - titanosauria also includes some of the smallest sauropods.

Titanosaurs had a remarkable global distribution during the Cretaceous, with fossil remains discovered on nearly every continent, adapting to a wide range of environments. They were especially diverse and abundant in the Southern Hemisphere, where most of the larger species have been found. In contrast, titanosaurs are notably rare in North America, where they appear to have largely disappeared for much of the Late Cretaceous. This uneven distribution may reflect changing environmental conditions, or competition with other herbivores.

As with all other non-avian dinosaurs alive at the time, the titanosaurs died out in the Cretaceous–Paleogene extinction event, marking the end the long-lived sauropod lineage.