There have been several prehistoric creatures that performed cannibalism. Such creatures include Dunkleosteus, Dimetrodon, and even Tyrannosaurus Rex. These animals would often target their own young. Sometimes they would try to eat their young after a few months and sometimes they attack their young as soon as they hatch. This practice may seem cruel, but it is a pragmatic survival strategy. The adults would weed out the weakest of the juveniles so that the strongest would thrive. This guarantees the long term survival of the species as a whole. Several of the carnivores in my dinosaur series perform this version of cannibalism.