Data from: Exceptionally preserved stomach contents of a young tyrannosaurid reveal an ontogenetic dietary shift in an iconic extinct predator (TMP 2009.12.14 Citipes tail segment)

Tyrannosaurids were large carnivorous dinosaurs that underwent major
changes in skull robusticity and body proportions as they grew, suggesting
they occupied different ecological niches during their lifespan. Although
adults commonly fed on dinosaurian megaherbivores, the diet of juvenile
tyrannosaurids is largely unknown. Here we describe a remarkable specimen
of a juvenile Gorgosaurus libratus that preserves the articulated
hindlimbs of two yearling caenagnathid dinosaurs inside its abdominal
cavity. The prey were selectively dismembered and consumed in two separate
feeding events. This predator-prey association provides direct evidence of
an ontogenetic dietary shift in tyrannosaurids. Juvenile tyrannosaurids
may have hunted small and young dinosaurs until they reached a size when,
to satisfy energetic requirements, they transitioned to feeding on
dinosaurian megaherbivores. Tyrannosaurids thus occupied both mesopredator
and apex predator roles during their lifespan, a factor that may have been
key to their evolutionary success.