on the parietals the anterolateral process of the parietal is expanded relative to the width of the posterolateral process the maxillary teeth are narrow and do not have denticles Additionally, Sekiya et al. (2013) add one more character distinguishing Y. huangi: a hemispherical neural spine in the posterior cervical vertebrae. Y. youngi According to Lu et al. (2007), Y. youngi can be distinguished from Y. huangi based on the following characteristics: the sixth cervical vertebra is the longest among the vertebral column the neural spines of the posterior cervical vertebrae are short with an expanded distal end, which is wider than its anteroposterior length three sacral vertebrae are tightly fused with a stout sacrocostal yoke the ventral margin of the postacetabular process of the ilium is slightly concave the ischium is longer than the pubis the distal end of the pubis is round Y. robustus According to Sekiya et al. (2013), Yunnanosaurus robustus can be distinguished from other sauropodomorphs based on the following characteristics: the absence of the anteroposterior expansion on the medial end of the astragalus the shaft of the metatarsal IV is dorsoventrally compressed Paleoecology 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. Chung Chien Young had also explored the lower dark/dull purple beds of the Shawan Member of the Lufeng Formation and found more specimens that he later assigned to Y. huangi. Specimen IVPP V32 was collected by Young in 1938 in dark red, argillaceous sandstone that is believed to have been deposited during the Hettangian stage