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Description
During South America's extended period of Cenozoic 'isolation', the Elasmarian Ornithopods underwent a rapid and extensive diversification event. A multitude of novel forms and lineages emerged, filling ecological niches that were taken by Ceratopsians, Parksosaurs, Rhabdodontians and Xiphosaurids on other continents. Indeed, aside from the Eusaurolophiform Hadrosaurs (which tended to be large grazers or mixed feeders), the Elasmarians were the only Ornithischian dinosaurs native to South America until the time of the Great American Interchange during the Pliocene. The sheer difference in body form can be observed in the picture above. The armoured 6m Osbornopeltid Uruguaypelta browses from a flower bearing Eudicot tree, while a family of the small slender Badjasauroid genus Janusuaurs feed on the fallen seeds and berries knocked to the ground by the larger animal. The former is a member of the Osbornopeltid subfamily Dryopeltinae, a group of narrow snouted browsing forms that first appear in the fossil record during the Middle Eocene. Uruguaypelta is the youngest and most derived Dryopeltine so far described, with the subfamily appearing to die out by the Oligocene-Miocene boundary. The reasons for this are not well studied, but climate change induced thinning of forested ecosystems and competition from herbivorous armoured Notosuchians may have played a part. Regardless, the Osbornopeltids as a whole would survive this period of stress, with the wide snouted grazing Brachypeltines going on to great success in the Miocene. Meanwhile, the Badjasauroids were a lineage of generally small and cursorial browsers and grazers that underwent a diversification event during the Late Eocene. Previously minor components of Eocene faunas, the more open environments of the Oligocene proved to their liking, with many new families proliferating. Among the most basal were the Salinasaurids, which resembled ancestral forms of the clade and remained fleet footed browsers. Janusaurus was a 2m genus with a widespread range, inhabiting Uruguay, Argentina and Bolivia throughout the Oligocene and comprising up to 4 species. More derived Badjasauroids would develop dense batteries of grinding teeth suitable for grazing and increasing cursorial adaptations.

Description
During South America's extended period of Cenozoic 'isolation', the Elasmarian Ornithopods underwent a rapid and extensive diversification event. A multitude of novel forms and lineages emerged, filling ecological niches that were taken by Ceratopsians, Parksosaurs, Rhabdodontians and Xiphosaurids on other continents. Indeed, aside from the Eusaurolophiform Hadrosaurs (which tended to be large grazers or mixed feeders), the Elasmarians were the only Ornithischian dinosaurs native to South America until the time of the Great American Interchange during the Pliocene. The sheer difference in body form can be observed in the picture above. The armoured 6m Osbornopeltid Uruguaypelta browses from a flower bearing Eudicot tree, while a family of the small slender Badjasauroid genus Janusuaurs feed on the fallen seeds and berries knocked to the ground by the larger animal. The former is a member of the Osbornopeltid subfamily Dryopeltinae, a group of narrow snouted browsing forms that first appear in the fossil record during the Middle Eocene. Uruguaypelta is the youngest and most derived Dryopeltine so far described, with the subfamily appearing to die out by the Oligocene-Miocene boundary. The reasons for this are not well studied, but climate change induced thinning of forested ecosystems and competition from herbivorous armoured Notosuchians may have played a part. Regardless, the Osbornopeltids as a whole would survive this period of stress, with the wide snouted grazing Brachypeltines going on to great success in the Miocene. Meanwhile, the Badjasauroids were a lineage of generally small and cursorial browsers and grazers that underwent a diversification event during the Late Eocene. Previously minor components of Eocene faunas, the more open environments of the Oligocene proved to their liking, with many new families proliferating. Among the most basal were the Salinasaurids, which resembled ancestral forms of the clade and remained fleet footed browsers. Janusaurus was a 2m genus with a widespread range, inhabiting Uruguay, Argentina and Bolivia throughout the Oligocene and comprising up to 4 species. More derived Badjasauroids would develop dense batteries of grinding teeth suitable for grazing and increasing cursorial adaptations.