Struthiomimus (meaning "ostrich mimic", from the Greek στρούθειος/stroutheios meaning "of the ostrich" and μῖμος/mimos meaning "mimic" or "imitator") is a genus of ornithomimid dinosaurs from the late Cretaceous of North America. Ornithomimids were long-legged, bipedal, ostrich-like dinosaurs with toothless beaks. The type species, Struthiomimus altus, is one of the more common small dinosaurs found in Dinosaur Provincial Park; its abundance suggests that these animals were herbivores or omnivores rather than pure carnivores.[1]
In 1901, Lawrence Lambe found some incomplete remains, holotype CMN 930, and named them Ornithomimus altus, placing them in the same genus as material earlier described by Othniel Charles Marsh in 1890. The specific name altus is from Latin, meaning "lofty" or "noble". However, in 1914, a nearly complete skeleton (AMNH 5339) was discovered by Barnum Brown at the Red Deer River site in Alberta, prompting O. altus to be described as the type genus of a new subgenus, Struthiomimus, by Henry Fairfield Osborn in 1917.[2] Dale Russell made Struthiomimus a full genus in 1972, at the same time referring several other specimens to it: AMNH 5375, AMNH 5385, AMNH 5421, CMN 8897, CMN 8902 and ROM 1790, all partial skeletons.[3] The type species, S. altus, is known from several skeletons and skulls,[4] In 1916 Osborn also renamed Ornithomimus tenuis Marsh 1890 into Struthiomimus tenuis.[2] This is today considered a nomen dubium. In 2016, ROM 1790 was made the holotype of a new genus and species, Rativates evadens.[5]
In subsequent years William Arthur Parks named four other species of Struthiomimus: Struthiomimus brevetertius Parks 1926,[6] Struthiomimus samueli Parks 1928,[7] Struthiomimus currellii Parks 1933 and Struthiomimus ingens Parks 1933.[8] These are today seen as either belonging to Dromiceiomimus or to Ornithomimus.
In 1997 Donald Glut mentioned the name Struthiomimus lonzeensis.[9] This was probably a lapsus calami, a mistake for Ornithomimus lonzeensis (Dollo 1903) Kuhn 1965. Struthiomimus altus comes from the Late Campanian (Judithian age) Oldman Formation.[10]
A possible second species of Struthiomimus is known from the early Maastrichtian (Edmontonian age) Horseshoe Canyon Formation. Because dinosaur fauna show rapid turnover, it is likely that these younger Struthiomimus specimens represent a species distinct from S. altus, though no new name has been given to them.[10][11]
Additional Struthiomimus specimens from the lower Lance Formation and equivalents are larger (similar to Gallimimus in size) and tend to have straighter and more elongate hand claws, similar to those seen in Ornithomimus. One relatively complete Lance Formation specimen, BHI 1266, was originally referred to Ornithomimus sedens (named by Marsh in 1892[12]) and later classified as Struthiomimus sedens.[13] One 2015 paper by van der Reest et al. listed BHI 1266 as Ornithomimus sp.,[14] while another paper the same year considered the specimen Struthiomimus sp. pending a re-evaluation of both genera.[10]