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[dinosaur] Giant aristonectine elasmosaurid from end Cretaceous of Antarctica

Ben Creisler


J.P. O'Gorman, S. Santillana, R. Otero & M. Reguero (2019)
A giant elasmosaurid (Sauropterygia; Plesiosauria) from Antarctica: new information on elasmosaurid body size diversity and aristonectine evolutionary scenarios.
Cretaceous Research (advance online publication)
doi: https://doi.org/10.1016/j.cretres.2019.05.004Â


The heaviest elasmosaurid worldwide is described.
The presence of this specimen, located less than 2.5 meters below the K/Pg boundary, indicates the persistence of aristonectines at high latitudes short time before the mass extinction
Elasmosaurids achieved maximum body size diversity during the Campanian-Maastrichtian
The development of the aristoenctine morphology, the increased body size and the cooling trend in the sea water are temporally and spatially correlated


Aristonectines show a highly derived morphology among elasmosaurid plesiosaurs, including some species with large body size. A new postcranial skeleton is described from the uppermost Maastrichtian levels of the LÃpez de Bertodano Formation, Seymour Island (= Marambio), Antarctica, being referred to as cf. Aristonectes sp; the most striking feature of the specimen described is its large body size, among the largest elasmosaurids worldwide. The occurrence of this specimen, located approximately 2.3 m or less below the K/Pg boundary, indicates the persistence of aristonectines at high latitudes and also it verifies their chronostratigraphical distribution until the end Cretaceous, before the mass extinction. Elasmosaurid diversity in terms of body size, possible relation of this body size, the trophic niche and abiotic drivers in aristonectine evolution are discussed. The body size inferred for MLP 89-III-3-1 seems to indicate an environment with high primary productivity, suggesting that these conditions persisted until the K/Pg mass extinction.

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