Therizinosaur moms stuck together to build nests and lay eggs. We know this because 15 fossil nests were found in one small area. One nest had 30 fossil eggs in it! The eggs were round and as big as grapefruits.
Scientists also found an egg with a full skeleton of a tiny therizinosaur inside. The baby had a big head and very large eyes, as most baby animals do today. The skeleton had strong bones. That means the baby could probably walk and find food right after hatching.