A scientist at Jurassic Park who created mutant embryos and then smuggled the eggs away; one day, his briefcase was stolen by Derrick and Abby, but he retrieved it. This was accomplished by engaging in a high speed Jeep chase, in which he drove Derrick and Abby off the road, causing them to crash. He then threatens Derrick with a knife not to interfere in his affairs as he takes his briefcase back.
The next day, when Gustavus was supposed to be in a meeting, Derrick and Abby went to his bunker and found multiple mutant dinosaurs; Gustavus arrived, and held them at gunpoint with his 9mm Beretta, firing a warning shot at them. He then explained that he was creating a race of super-dinosaurs. He prepares to shoot the two, but the bunker quakes as the ledge it is on starts to collapse.
Derrick and Abby escape, but Gustavus follows; he is about to shoot them again, this time with an assault rifle, when he is attacked by a Dilophosaurus and is gravely injured. He returns to the bunker to kill Derrick and Abby, but a mutant chick wielding the Berreta he had dropped from earlier accidentally shoots him. Dying, he remains in the bunker as it collapses away.