Continuity mistake: When Travis goes to visit Dr. Rand to tell her what happened, she sticks a shotgun through the opening in the door to drive him off. Once he explains who he is, we hear the door unlock. In the next shot, when Travis walks in, Dr. Rand is instantly on the other side of the huge penthouse.
Plot hole: Travis does the last time jump to change the events of a previous time jump. As all the jumps were to the exact same time to kill the same dinosaur, the travelers of the second jump must have found there the travelers of the first one. The travelers of the third jump must have found the travelers of the second and the first, and so on.
Continuity mistake: The scientist draws concentric rings while saying, "We seem to be stuck ahead of the changes that are occurring." She then puts a dent in the rings. The shot changes to the government guy who responds, "What do we do?" When the shot goes back to her, the rings are in their original undented state as she replies, "Let me work on it." (00:50:08)
Factual error: The trip goes back 65 million years. This is the late Cretaceous period. The Allosaurus was a Jurassic period dinosaur, which became extinct before the beginning of the Cretaceous period. Granted, the Allosaurus was probably the most powerful predator of its time, the events in this movie take place long after the time of the Allosaurus.
Plot hole: How could a species extinction cause a volcanic eruption? It makes no sense.