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.
Shonisaurus
"Shonisaurus" lived during the Norian stage of the late Triassic period. "S. popularis" measured around long. A second species from British Columbia was named "Shonisaurus sikanniensis" in 2004. "S. sikkanniensis" was one of the largest marine reptiles of all time, measuring . However, phylogenetic studies later showed "S. sikanniensis" to be a species of "Shastasaurus" rather than "Shonisaurus".
A new study published in 2013 reasserted the original classification, finding it more closely related to "Shonisaurus" than to "Shastasaurus". Specimens belonging to "S. sikanniensis" have been found in the Pardonet Formation British Columbia, dating to the middle Norian age (about 210 million years ago).