Erenhot (Iren-Nur ) is located right on the border between China and Mongolia. This town represents one of many Chinese entrances to southern Mongolia. It has a counterpart on the Mongolian territory, the town of Za-Monwudia. Erenhot was built on a lowland landscape called the Eren Basin by geologists. There is a small salt lake just seven kilometers northeast of the town. Gray-green, pinkish mudstone exposed around the lake is believed to represent freshwater deposits. The thickness of these depositis is about 57 to 59 meters. Plenty of dinosaur bones and egg fossils have been unearthed at this site.
The Central Asiatic Expeditions conducted two major excavations at the Eren Basin. In 1933, C. Gilmore, who studied fossils from the basin, described two primitive hadrosaurs, Bactrosaurus johnsoni and Mandschurosaurus mongnliensis.Both taxa were reexamined by Brett-Surman in 1980, latter refer now to a single taxon of Gilmoresaurus mongoliensis. The basin is so rich for ornithomimid dinosaurs that one could say that as long as you bend down, you can pick up a fossil bone. Gilmore worked on a collection of ornithomimid bones and found these bones belong to a single species that he named as Ornithomimus asiaticus. Later on, D. Russell of the Canadian National Museum restudied the collection and changed the generic name for Archaeomithimus .