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Stegosaur from Early Cretaceous of Argentina



From: Ben Creisler
bcreisler@gmail.com


A new online paper in Alcheringa:

Xabier Pereda-Suberbiola, Peter M. Galton, Heinrich Mallison &
Fernando Novas (2012)
A plated dinosaur (Ornithischia, Stegosauria) from the Early
Cretaceous of Argentina, South America: an evaluation.
Alcheringa (advance online publication)
DOI:10.1080/03115518.2012.702531
http://www.tandfonline.com/doi/abs/10.1080/03115518.2012.702531



A re-evaluation of several vertebrae and dermal plates from the Lower
Cretaceous (La Amarga Formation, Puesto Antigual Member;
Barremian–lower Aptian) of Neuquén in Argentina, originally described
as a stegosaurian dinosaur and recently referred to an indeterminate
ornithischian, confirms the former identification. The Neuquén remains
have a combination of features that is only known among stegosaurs:
cervical vertebrae with a proportionally large cross-section of the
neural canal, the anterior height and width of which are half the
height of the anterior centrum, as in the cervical vertebrae of
Kentrosaurus, Dacentrurus and Stegosaurus; prominent lateral
depressions on the cervical centra, as in the presacral vertebrae of
Dacentrurus; and cervical dermal plates that are subtriangular, longer
than high and reminiscent of those of Miragaia. Moreover, a small bone
here interpreted to be an anterior supraorbital (= first palpebral) is
similar to that of Stegosaurus and other stegosaurs in having an
elongate form and a dorsal rugose surface. The remains from Argentina
exhibit some differences relative to other stegosaurs, suggesting that
it is potentially a distinct taxon, but their incompleteness advises
against the erection of a new genus and species. Interestingly, it is
the only known skeletal record of Stegosauria in South America. It
provides the second conclusive evidence of the presence of this clade
in the Early Cretaceous of the Gondwanan landmasses.