definition were adopted. Another clade, Ornithomimiformes, was defined by Sereno (2005) as (Ornithomimus velox > Passer domesticus) and replaces the more inclusive use of Ornithomimosauria when alvarezsaurids or some other group are found to be closer relatives of ornithomimosaurs than maniraptorans, with Ornithomimosauria redefined to include dinosaurs closer to Ornithomimus than to alvarezsaurids. Gregory S. Paul has proposed that Ornithomimosauria might be a group of primitive, flightless birds, more advanced than Deinonychosauria and Oviraptorosauria. The cladogram below follows an analysis by Yuong-Nam Lee, Rinchen Barsbold, Philip J. Currie, Yoshitsugu Kobayashi, Hang-Jae Lee, Pascal Godefroit, François Escuillié & Tsogtbaatar Chinzorig. The analysis was published in 2014, and includes many ornithomimosaurian taxa. The cladogram below follows the phylogenetic analysis by Scott Hartman and colleagues in 2019, which has included a vast majority of species and uncertain specimens, resulting in a novel phylogenetic arrangement. Below is a cladogram by Serrano-Brañas et al., 2020, showing an analysis more in line with previous assumptions about ornithomimosaur classification. Palaeobiology Ornithomimosaurs probably acquired most of their calories from plants. Many ornithomimosaurs, including primitive species, have been found with numerous gastroliths in their stomachs, characteristic of herbivores. Henry Fairfield Osborn suggested that the long, sloth-like "arms" of ornithomimosaurs may have been used to pull down branches on which to feed, an idea supported by further study of their strange, hook-like hands. The sheer abundance of ornithomimids — they are the most common small dinosaurs in North America — is consistent with the idea that they were plant eaters, as herbivores usually outnumber carnivores in an ecosystem. However, they may have been omnivores that ate both plants and small animal prey. Comparisons between the scleral rings of two ornithomimosaur genera (Garudimimus and Ornithomimus) and modern birds and reptiles indicate that they may have been cathemeral, active throughout the day at short intervals. Social behavior Ornithomimosaurs are fairly well known for their gregarious life-styles. Some of the first findings of ornithomimosaur bonebeds were reported from the Iren Dabasu Formation in 1993 by Charles W. Gilmore. The bonebed consisted of numerous individuals of Archaeornithomimus ranging from young to adult remains. Multiple specimens of Sinornithomimus were collected from a single monospecific bonebed with a considerable density of juvenile individuals—out of 14, 11 were juveniles—, suggesting a gregarious behavior for an increased protection from predators. The notable abundance of juveniles indicates a high mortality in them or that a large mass-mortality event of