I once had a Petra egg she was a very high level o gave here 3 stacks of food when she got strong enough I had to go for a couple hours when I came back they were gone without a trace the logs did not indicate that they died but I think they starved rip Petra jr
One time I was on a raft with some people in my tribe we encountered a guy with one but we did not know they swam super fast he did not destroy us he wanted one of our ankylosaurs we gave it to him and survived.