The Reptilians were genetically bred from several different species of prehistoric reptiles, mainly aquatic ones.
Two Reptilians started attacking H.E.A.T. when they entered the Tachyons' Leviathan ship. Monique Dupre pulled out her gun and shot at them. The Reptilians started to chase her and the H.E.A.T. crew down. The H.E.A.T. crew hit a dead end shortly after, but Nick Tatopoulos backed up into a fleshy wall and it opened up. The crew went in and it closed after Monique entered, leaving the Reptilians behind.
The Reptilians have several tentacles connected to their jaws. They can extend as long to reach to their targets.