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Sidersaura

MEANING: Star lizard

PERIOD: Late Cretaceous

CONTINENT: South America


Rebbachisaurids like Sidersaura are the last known diplodocoids. They lived alongside the titanosaurs until fairly late in the Cretaceous before disappearing from the fossil record, presumably going extinct. They had long tails and short necks, by sauropod standards. Sidersaura was large for a rebbachisaurid, growing to about 20 m in length.


Sidersaura

Abstract from paper: Rebbachisauridae is mainly recorded during the early Late Cretaceous in Gondwana, and in South America in particular. Sidersaura marae gen. et sp. nov. was found in rocks of the Huincul Formation (upper Cenomanian – Turonian) of Neuquén Province, Argentina. Sidersaura has notable characteristics that allow recognising it as a new species and defining its phylogenetic relationships. First, it has a frontoparietal foramen, as in dicraeosauridae. It bears fourteen caudal vertebrae with neural arches displaced closer to the anterior margin of the centrum and a ventral longitudinal hollow on middle of the centra, both characters previously considered as titanosaurian synapomorphies, and here recognised in these diplodocoid sauropods. Sidersaura shows a peculiar tarsal condition with an unusual calcaneum morphology which resembles that of basal sauropods. The haemal arches have a stellate morphology with two sets of projections comparable to the specimen MMCh-PV 47 from the Candeleros Formation (Cenomanian), previously described as a titanosaurian. The phylogenetic analysis retrieves Sidersaura as a basal Rebbachisauridae more closely related to Zapalasaurus than to Limaysaurinae. The presence of a basal taxon at Cenomanian – Turonian times, so close to the extinction of the group, implies that the evolutionary history of rebbachisauridae was more complex than previously thought.



Sidersaura 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.


Sidersaura 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.

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