Abdominal Contents from Two Large Early Cretaceous Compsognathids (Dinosauria: Theropoda) Demonstrate Feeding on Confuciusornithids and Dromaeosaurids

Abstract

Two skeletons of the large compsognathid 'Sinocalliopteryx gigas' include intact abdominal contents. Both specimens come from the Jianshangou Beds of the lower Yixian Formation (Neocomian), Liaoning, China. The holotype of 'S. gigas' preserves a partial dromaeosaurid leg in the abdominal cavity, here attributed to 'Sinornithosaurus'. A second, newly-discovered specimen preserves the remains of at least two individuals of the primitive avialan, 'Confuciusornis sanctus', in addition to acid-etched bones from a possible ornithischian. Although it cannot be stated whether such prey items were scavenged or actively hunted, the presence of two 'Confuciusornis' in a grossly similar state of digestion suggests they were consumed in rapid succession. Given the lack of clear arboreal adaptations in 'Sinocalliopteryx', we suggest it may have been an adept stealth hunter.