INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
capítulos de libros
Paleobiology of South American titanosaurs
GONZÁLEZ RIGA, BERNARDO J.
Paleontología y dinosaurios desde América Latina
EDIUNC, Editorial de la Universidad Nacional de Cuyo
Lugar: Mendoza; Año: 2010; p. 125 - 141
South American titanosaur studies are shedding light on to diverse phylogenetic and paleobiological topics. From a cladistic viewpoint, different clades have been recognized (Lognkosauria, Rinconsauria, Aeolosaurini, Saltasaurinae), revealing a greater diversity of Late Cretaceous herbivorous dinosaur faunas. In most titanosaur taxa skull characters are unknown; this aspect must be carefully considered in phylogenetic analyses. At present, to test these interpretations, more detailed cladistic analysis including all new titanosaur species recently discovered in South America (Brazil, Argentina), Africa, and Asia are necessary. From a paleobiological viewpoint, several new discoveries are important. Ontogenetic topics have been studied through embryos and osteohistology. First, the discovery of exceptionally preserved embryos, eggs, and nests at Auca Mahuevo (Neuquén Province, Patagonia) has produced new ontogenetic and phylogenetic information. Second, new osteohistological studies promise to provide insight into the growth strategies of titanosaurs. These analyses will also be important for understanding evolutionary aspects, when osteohistological sections of most relevant sauropod species become available. Third, detailed sedimentological and taphonomic analyses of bone assemblages have supported systematic studies, indicating the association of different specimens and the in situ position of articulated bones. Moreover, such analyses yield information about the environments where titanosaurs lived. Finally, the ichnological record offers valuable information about different strategies of titanosaur locomotion and behavior. For example, in Argentina two sauropod ichnotaxa have been named: Sauropodichnus giganteus Calvo, from the early Cenomanian of Neuquén Province, and Titanopodus mendozensis González Riga and Calvo, from the late Campanian-early Maastrichtian of Mendoza Province. Sauropodichnus footprints show a wide gauge trackway, and were probably produced by basal titanosaurs. Titanopodus footprints were discovered at the Agua del Choique track site and offer an excellent example of the wide-gauge style of locomotion. This track site comprises more than 250 tracks produced by Late Cretaceous sauropods, probably medium-sized saltasaurine or aeolosaurine titanosaurs. Tracks are preserved on a calcareous sandstone bed of the Loncoche Formation. Most of the trackways are parallel and show the same direction of travel suggesting that titanosaurs moved in social groups. This discovery constitutes the second piece of evidence of gregarious sauropod behavior recorded in South America; the first was documented in Late Cretaceous strata of Bolivia. From a paleoenvironmental point of view, the ocurrence of sauropod tracks in tidal facies of the Loncoche Formation is not direct evidence of a permanent habitat for these huge vertebrates. Instead, this record indicates that some titanosaurs had the capacity to walk across marginal marine environments, in this case related to the Late Cretaceous Atlantic transgression that covered central-northern Patagonia during the Maastrichtian-Paleogene.