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When it was first described, in 1993, Shuvosaurus was thought to be a very early ornithomimid, the "bird mimic" dinosaurs that roamed Cretaceous Eurasia and North America in vast herds. Later study revealed, however, that ornithomimids were unlikely to have evolved way back in the late Triassic period, so the beaked, toothless Shuvosaurus has now been tentatively assigned as an archosaur rather than an early theropod. Future fossil discoveries may tip the balance one way or the other.
By the way, the name of the only species of this ancient reptile (Shuvosaurus inexpectus) refers to the fortuitous nature of its discovery; "Shuvo" is the son of the paleontologist who found the bones.