Gillicus was a medium sized fish from the late Cretaceous, it was probably a food source for large predators like Tylosaurus, Xiphactinus and sharks. Gillicus fed on smaller fish or algae. There is a famous fossil of Gillicus after it was eaten by a Xiphactinus. The Gillicus was eaten whole which caused the Xiphactinus' death.
Jurassic Park Inspired Games
Gillicus can be created in Jurassic Park: Builder. Though it requires dino-dollars purchase.
see Gillicus/JW: TG
Gillicus was added as a new tournament cave in the game on June 13th, 2018.