Crocodiles have a smooth, cylindrical penis with an external groove to carry sperm and a tip that resembles a mammal's penis. Some experts suppose that's what a Titanosaur's penis probably looked like as well. It all leads to an irresistible question; what about size? Just how big are the bits of a creature that's as long as a four-story building is tall? If body size is any indicator, the Titanosaur could have had a penis that's up to 12 feet long.