Cienciargentina

MEANING: Argentine science

PERIOD: Late Cretaceous

CONTINENT: South America

Rebbachisaurids are the latest known sauropod dinosaurs outside the titanosaur lineage. Cienciargentina is a rebbachisaurid from the Late Cretaceous, making it among the most recent. It had many hollow bones, and likely had batteries of teeth used for chewing, a rebbachisaurid feature unique among sauropods.

Abstract from paper: Cienciargentina sanchezi gen. et sp. nov. is a new rebbachisaurid sauropod dinosaur from the Late Cretaceous of Argentina. The new species is erected on the basis of a unique combination of characters that includes many autapomorphies, among them: cervical epipophyses absent, anterior dorsal centra amphicoelous to slightly opisthocoelous, posterior dorsal centrum slightly opisthocoelous, posterior dorsal neural spines anteroposteriorly extended, mid and posterior dorsal vertebrae with intrapostzygapophyseal lamina supporting the postzygapophyses from below, middle and posterior dorsal vertebrae with accesory spinodiapophyseal lamina, lateral laminae in anterior caudal vertebrae formed by the spinoprezygapophyseal lamina and the spinopostzygapophyseal lamina, which fuse at the middle of the neural spine, anterior caudal vertebrae with spinoprezygapophyseal lamina more robust than spinopostzygapophyseal lamina, anterior caudal transverse processes with a full suite of diapophyseal laminae (anterior centrodiapophyseal lamina, posterior centrodiapophyseal lamina, prezygodiapophyseal lamina, postzygodiapophyseal lamina), ratio of length to height of the posterior caudal vertebrae 5 or higher, forked chevrons without anterior and posterior projections, and femoral head dorsally directed, rising well above the level of the greater trochanter. This new species is added to the list of rebbachisaurid sauropods documented in the Huincul Formation (upper Cenomanian-Turonian), which are thought to be the latest diplodocoids at global level. In fact: from the Turonian onwards, sauropod communities are composed exclusively of macronarians, mostly titanosaurs. In Patagonia, particularly in the Huincul Formation, the hypothetical faunal turnover that occurred in the middle of the Cretaceous, which involved not only sauropods but other groups of dinosaurs, is observed, perhaps like nowhere else in South America.

Cienciargentina 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.

Cienciargentina is a sauropod. Sauropods are saurischian dinosaurs that had very long necks, long tails, small heads (relative to the rest of their body), and four thick, pillar-like legs. They are notable for the enormous sizes attained by some species, and the group includes the largest animals to have ever lived on land. Well-known genera include Brachiosaurus, Diplodocus, Apatosaurus and Brontosaurus.

The oldest known unequivocal sauropod dinosaurs are known from the Early Jurassic, and by the Late Jurassic (150 million years ago), sauropods had become widespread. By the Late Cretaceous, one group of sauropods, the titanosaurs, had replaced all others and had a near-global distribution. This group included the largest animals ever to walk the earth. Estimates vary, but the largest titanosaurs are estimated at upward of around 40 m, and weighing 100 t, or possibly even more.

As with all other non-avian dinosaurs alive at the time, the titanosaurs died out in the Cretaceous–Paleogene extinction event. Fossilized remains of sauropods have been found on every continent, including Antarctica.