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.
Sinraptor
The holotype specimen of "Sinraptor" was uncovered from the Shishugou Formation during a joint Chinese/Canadian expedition to the northwestern Chinese desert in 1987, and described by Philip J. Currie and Zhao Xijin in 1994. Standing nearly tall and measuring roughly in length, two species of "Sinraptor" have been named. "S. dongi", the type species, was described by Currie and Zhao in 1994. A second species, originally named "Yangchuanosaurus hepingensis" by Gao in 1992, may actually represent a second species of "Sinraptor". Whether or not this is the case, "Sinraptor" and "Yangchuanosaurus" were close relatives, and are classified together in the family Metriacanthosauridae.