Ornithischian and theropod dinosaurs were morphologically diverse during the Cretaceous. In contrast, sauropods were relatively more conservative. The anatomy of Bonitasaura salgadoi, a new 9-m titanosaurian sauropod from Upper Cretaceous beds of Patagonia, suggests that sauropod anatomical diversity would have included unexpected items. Its unusual, rectangular lower jaw possesses narrow, anteriorly restricted teeth and shows evidence of a sharp keratinous sheath over the non-dentigerous region that probably worked to guillotine plant material. This discovery definitely demonstrates that titanosaurs acquired a mandibular configuration similar to that of some basal diplodocoids, as had already been suggested by the lower jaw of the controversial genus Antarctosaurus. This oral configuration, plus the beak-like structure and the skull shape, resemble some traits more commonly seen in Laurasian ornithischians, mostly unexpressed in southern continents. A high sauropod morphological diversity seems to be in agreement with the poorly represented ornithischian clades of the southern hemisphere.
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The work was supported by the Jurassic Foundation and Paleogenesis. I gratefully acknowledge the assistance of the Pincheira and Ávila families and thank them for their kind help. Thanks to Mr. Parodi for guiding us to the fossil site and to Marcos Zúñiga and the Salinas family for logistics. P.A. Gallina, F.L. Agnolin, G. Lio, L. Gaetano, M. Cardenas, M. de la Fuente, L. Ballarino, F. Pose, are thanked for field support. Thanks to the geologists Hugo Corbela and Hector Leanza for the stratigraphic position of the specimen. I am grateful to J.A. González for illustrations and M. Isasi for preparation. M. Lamanna, J.F. Bonaparte and P.J. Makovicky substantially improved this work with useful comments and critical reviews.
Communicated by G. Mayr
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Apesteguía, S. Bonitasaura salgadoi gen. et sp. nov.: a beaked sauropod from the Late Cretaceous of Patagonia. Naturwissenschaften 91, 493–497 (2004). https://doi.org/10.1007/s00114-004-0560-6