The type specimens of "Yunnanosaurus huangi" and "Yunnanosaurus robustus" were recovered in the Huangchiatien (Dahungtien) locality of the Lufeng Formation in Yunnan, China. The "Y. huangi" holotype specimen IVPP V20 and the "Y. robustus" holotype specimen IVPP V93, were collected by Chung Chien Young in terrestrial sediments from the upper dark/deep red beds of the Zhangjiawa Member of this formation, that are believed to have been deposited during the Sinemurian stage of the Jurassic period, approximately 199 to 190 million years ago. Several other specimens assigned to "Y. huangi" (IVPP V54, IVPP V47, IVPP V61, IVPP V62, IVPP V63, IVPP V96, IVPP V264), and "Y. robustus" (IVPP V39, IVPP V94) were also recovered by Young in this locality. These specimens are all housed in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology, in Beijing, China. In the years to come several more specimens assigned to these two species were recovered from Zhangjiawa Member of this formation.