I regularly kill these bois with my 3 spinos and a giga. Not water boosted but I do give them the courage boost with a Yuty. Mind you that, my spinos have 36k hp & 2k dm & the giga is at 32k & 605 dm. Definitely not a dinosaur you wanna take lightly at all lol.
Easily killable with a wyvern. Lightning and poison easiest down to longer range in attack. Just hover above and light it up :) killed my first today and it didn't touch me once. Just remember to watch stamina ;)