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.
Spinosauridae
The subfamily Spinosaurinae was named by Sereno in 1998, and defined by Holtz and colleagues in 2004 as all taxa closer to "Spinosaurus aegyptiacus" than to "Baryonyx walkeri". And the subfamily Baryonychinae was named by Charig & Milner in 1986. They erected both the subfamily and the family Baryonychinae for the newly discovered "Baryonyx", before it was referred to the Spinosauridae. Their subfamily was defined by Holtz and colleagues in 2004, as the complementary clade of all taxa closer to "Baryonyx walkeri" than to "Spinosaurus aegyptiacus". Examinations in 2017 by Marcos Sales and Cesar Schultz indicate that the South American spinosaurids "Angaturama" and "Irritator" were intermediate between Baronychinae and Spinosaurinae based on their craniodental features and cladistic analysis. This indicates that Baryonychinae may in fact be non-monophyletic. Their cladogram can be seen below.