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.
Sinocalliopteryx
The well-preserved skeleton of the "Sinocalliopteryx" holotype contained the partial leg of a dromaeosaurid within the abdominal cavity, comprising a complete lower leg and foot with toes and claws in their natural, articulated position. While the leg part, about one foot long, is very large in relation to the abdominal cavity, it is clearly situated within it, lying between the ribs. Ji and colleagues in 2007 suggested that this could indicate it preyed upon the smaller, bird-like dinosaur. This discovery indicated that "Sinocalliopteryx" may have been an agile, active, "fierce" predator, especially since other compsognathids have been found with (presumably fast-moving) lizards and small mammals in their abdominal cavities. In 2012 the dromaeosaurid was tentatively identified as an individual of "Sinornithosaurus" with a length of 1.2 metres (3.9 ft). The 2012 study also reported newly discovered remains of prey animals. Above the dromaeosaurid leg, feathers are visible. Below it two clusters of digested food can be seen. It was suggested that the feathers had belonged to a bird and were with the leg still present in the stomach. The digested food would, using the preserved digestive tract of "Scipionyx" as a reference, have been positioned in the duodenum. The C-shaped abdominal contents of this specimen appear to reflect of the original contour of the digestive tract.