A new basal iguanodontian (Dinosauria, Ornithischia) from the Upper Cretaceous of Patagonia

摘要

We report the discovery of an almost complete skeleton of a new iguanodontian dinosaur, Talenkauen santacrucensis n. gen. et sp., from Maastrichtian rocks of southwestern Patagonia. Talenkauen is odd in the presence of plate-like structures on both sides of the thorax, which are better interpreted as uncinate processes than dermal armor. Talenkauen and the also Maastrichtian Thescelosaurus neglectus Gilmore from North America, represent the only two ornithischians in which this peculiar feature is currently known. Some derived features unite Talenkauen with other Gondwanan ornithopods, but all the evidence does not offer enough support for an iguanodontian clade endemic from the Southern Hemisphere. Small- to medium-sized ornithischians appear to have been the dominant plant-eating dinosaurs in Antarctica and Australia during the Cretaceous, in contrast with the outstanding abundance of medium sized to giant sauropods in central Gondwana (e.g., South America, Africa, India).