/u/Georgy_K_Zhukov and I posted about 'sharkmouth' designs in [this thread] (https://www.reddit.com/r/AskHistorians/comments/51eu4u/what_is_the_first_recorded_usage_of_the_shark/), drawing heavily on Richard Ward's Sharkmouth books from Osprey. The mouth design appears to have originated on a Roland C.II in World War I, though no specific event seems to have prompted it.