Owen escapes from the Tyrannosaur when an object becomes lodged in the creature's jaw, making it unable to close, similar to how Luke Skywalker escapes the rancor in Star Wars: Episode VI - Return of the Jedi (1983). The rancor's behavior has already been referenced by the tyrannosaur once before, as the shot of it devouring the goat before looking down at the car in Jurassic Park (1993) was also taken from the rancor pit.
It's established that Owen's raptors are hatched on Wednesday, May 23rd 2012.