You see a triceratops standing in front of a full moon and you can't help but see a really strong resemblance. The triceratops has that round frill thing behind its horns and it looks just like the round full moon. Who knew that a triceratops would resemble the moon!
The first person to see this resemblance was the Shougun (しょう). That's why he decided to put a triceratops head with the moon behind it on his mon (family crest). Now he's known as the full moon dinosaur shogun, and he's very famous.