Elasmaria is aclade ofornithopods known fromCretaceous deposits in South America, Antarctica, and Australia that contains many bipedal ornithopods that were previously considered"hypsilophodonts".[1][2]
Calvoet al. (2007) coined Elasmaria to accommodateMacrogryphosaurus andTalenkauen, which they recovered as basal iguanodonts distinct from other iguanodontians in having mineralized plates on the ribs.[3] In 2016, a paper describing the genusMorrosaurus found Elasmaria to be far larger than its initial contents of two taxa, instead containing a variety of ornithopods from theSouthern Hemisphere.[4] In 2021, under thePhylocode, Madziaet al. (2021) formally defined Elasmaria as "the smallest clade containingMacrogryphosaurus gondwanicus andTalenkauen santacrucensis, provided that it does not includeHypsilophodon foxii,Iguanodon bernissartensis, orThescelosaurus neglectus.[5] Fonsecaet al. (2024) redefined Elasmaria as "the largest clade containingMacrogryphosaurus gondwanicus andTalenkauen santacrucensis but notDryosaurus altus,Hypsilophodon foxii,Iguanodon bernissartensis, andThescelosaurus neglectus" so that it included more related taxa. The cladogram below follows their preferred reference phylogeny, taken from the results of their own study.[6]
