When they come across a stegosaurus, Mitch tells Tiff to "stay clear of its thagomizer" - the stego's spiked tail. This is a reference to a "Far Side" comic strip, where cavemen named the stego's tail Thagomizer after "the late Thag."
Hap closely resembles Robert Muldoon from the original film. He also (presumably) dies in a similar fashion, being dispatched by a pack of dinosaurs working as a team while safeguarding the lives of others.