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Description
The Plenosauroids were a distinctive lineage of Elasmarian Ornithopods that inhabited environmental niches similar to those of the Ceratopsians. First emerging during the Early Eocene, basal members were small and firmly bipedal but already were developing the powerful jaws and slicing teeth that were so characteristic of this lineage. By the end of the Eocene, the derived clade Taurosauroidea had diverged, to which all Oligocene and Miocene members belonged. These were bulky, heavy-set animals adapted for chewing and processing tough vegetation, with proportionally large square skulls. Ranchoverdedon was a Late Oligocene genus known from fossil remains recovered from Argentina and Uruguay, represented by several specimens of up to three species. R. monesi was endemic to Uruguay, measuring up to 5m long and weighing in at over 1 tonne. The animal possessed a pair of short brow horns above the eyes, as well as a large nasal ridge probably used as a form of display and species recognition. Unlike the very distantly related Ceratopsians of the Northern Hemisphere, Plenosauroids lacked an expanded bony neck frill and greatly elongated horns, although the vertical chopping tooth batteries were superficially very similar. This slow moving species likely dwelt in herds as a form of protection from predators, particularly the Pelorosaurine Megaraptorans and the Baurusuchid Notosuchian Pantherachampsa, inhabiting more densely wooded areas away from open country. The Plenosauroids were a successful group, producing a large number of genera throughout the Miocene and into the Pliocene. However, these animals would suffer greatly during the American Faunal Interchanges of the latter period, vanishing from the fossil record approximately 4 million years ago to ironically be replaced by true Ceratopsians.

Credit to Sheather888 for the artwork.

Description
The Plenosauroids were a distinctive lineage of Elasmarian Ornithopods that inhabited environmental niches similar to those of the Ceratopsians. First emerging during the Early Eocene, basal members were small and firmly bipedal but already were developing the powerful jaws and slicing teeth that were so characteristic of this lineage. By the end of the Eocene, the derived clade Taurosauroidea had diverged, to which all Oligocene and Miocene members belonged. These were bulky, heavy-set animals adapted for chewing and processing tough vegetation, with proportionally large square skulls. Ranchoverdedon was a Late Oligocene genus known from fossil remains recovered from Argentina and Uruguay, represented by several specimens of up to three species. R. monesi was endemic to Uruguay, measuring up to 5m long and weighing in at over 1 tonne. The animal possessed a pair of short brow horns above the eyes, as well as a large nasal ridge probably used as a form of display and species recognition. Unlike the very distantly related Ceratopsians of the Northern Hemisphere, Plenosauroids lacked an expanded bony neck frill and greatly elongated horns, although the vertical chopping tooth batteries were superficially very similar. This slow moving species likely dwelt in herds as a form of protection from predators, particularly the Pelorosaurine Megaraptorans and the Baurusuchid Notosuchian Pantherachampsa, inhabiting more densely wooded areas away from open country. The Plenosauroids were a successful group, producing a large number of genera throughout the Miocene and into the Pliocene. However, these animals would suffer greatly during the American Faunal Interchanges of the latter period, vanishing from the fossil record approximately 4 million years ago to ironically be replaced by true Ceratopsians.

Credit to Sheather888 for the artwork.