dinosaur cocks!
Okay, so the conversation wound up on crocodilian penis b/c furries. I had no clue what crocodilian penes are like and found;
Ducks have a similar structure! So I wondered, maybe all archosaur cocks including dinosaurs, work the same way?
I checked and both icthyosaurs and pleiosaurs retain a pelvis. Cetaceans have a similar muscular action/anchor thing going on, but otters and seals have erectile cocks so I don't think it's just an aquatic adaptation.