The herrerasaurus was a type of theropod dinosaur. They were small predators, only five feet long and three hundred pounds, but fast and very vicious. They had excellent vision and hearing and a powerful sense of smell.
The herrerasaurus was one of the species the Silurians brought back from extinction after they took over in a parallel world. Packs of herrerasaurus were used by the Silurians in their hunts, being sent first to tear apart the prey. They were trained by flute signals, and were fearless during the hunt. They would also be telepathically controlled by the Silurians for more complex tasks. (PROSE: Blood Heat)