Sinosauropteryx
Three specimens have been assigned to "Sinosauropteryx prima": the holotype GMV 2123 (and its counter slab [opposite face], NIGP 127586), NIGP 127587, and D 2141. Another specimen, IVPP V14202, was assigned to the genus but not to the only species by Zhang and colleagues. The assignment of an additional larger specimen to "S. prima", GMV 2124, was later found to be in error. All of the fossils were found in the Jianshangou or Dawangzhangzi Beds of the Yixian Formation in the Beipiao and Lingyuan regions of Liaoning, China. These fossil beds have been dated to 124.6–122 million years ago, during the early Aptian stage of the Early Cretaceous.
Sanchiaosaurus
"Sanchiaosaurus" is known solely from the holotype IVPP V3228, a partial skeleton housed at the Institute of Vertebrate Paleontology and Paleoanthropology. This skeleton is exposed in ventral view, i.e. from below, and preserves the skull and lower jaw, 1 isolated tooth and a partially preserved postcranial skeleton. IVPP V.3228 was collected near the Jinzhong Bridge, in the suburbs of Guiyang City, Chinchungchiao, Sanchiao in the vicinity of Guiyang, Guizhou Province, from the first member of the Guanling Formation, dating to the Anisian stage of the early Middle Triassic, about 245 million years ago.