MEANING: Indomitable lizard
PERIOD: Late Cretaceous
CONTINENT: South America
Chucarosaurus is a titanosaurian sauropod dinosaur from the Late Cretaceous of Argentina, known from fairly intact remains of the left limbs, including a 1.9 m femur. It was a large, slender-limbed colossosaur - 30 m in length, and weighing around 50 t. Characteristics in its hips, forelimbs, and hindlimbs suggest that despite its massive size, Chucarosaurus was slender and more gracile than would be otherwise expected for such a large animal.
Abstract from paper: Chucarosaurus diripienda gen. et sp. nov. is a new and large titanosaurian sauropod from the Neuquén Basin, Rio Negro Province, Patagonia. The specimen was discovered in the Upper Cretaceous strata of the Huincul Formation (middle Cenomanian–lower Turonian). It includes appendicular and relatively slender elements, with a femoral total length of about 1.9 m long. This taxon shows a unique combination of characters indicating that appendicular bones such as the femur, ischium and tibia, show a remarkable morphological variety, greater than previously described, and are morphologically informative as source of phylogenetic data. A cladistic phylogenetic analysis placed Chucarosaurus well nested within the Colossosauria clade.
Chucarosaurus is from the Cretaceous. The Cretaceous is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period.
The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct flora and fauna, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth by the end of the Cretaceous, coincident with the decline and extinction of previously widespread gymnosperm groups.
The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary (K–Pg boundary), a geologic signature associated with the mass extinction that lies between the Mesozoic and Cenozoic Eras.
Chucarosaurus 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.