The Octosaurs originated in the Goo Caverns, where Dr. Rex had a secret laboratory. Whether they were created by him, or by Dr. Inferno or Dr. Wolf, who also had secret laboratories in the Goo Caverns, is unknown. What is known is that after being created they fled into the submerged passageways of the Goo Caverns. These passageways, once used by Ogel to move forces quickly between the Caverns and his aquatic bases, were long abandoned and the Octosaurs ensured they stayed that way, by killing anything that tried to go through them.
Former Alpha Team Agent and former Pirate-turned Dino Attack Agent Coral led a submarine through one of these passageways, where he used computer hacking to open the gates. Upon opening the gates, two massive, old Octosaurs emerged, and Coral was able to make Ogel's formidable defenses open fire and pulverize them. Coral's ship continued into the passageways, narrowly dodging more Octosaurs heading for the opened gates (and to be pulverized by the underwater cannons).
Younger, amphibious Octosaurs emerged when a Dino Attack team under the command of Reptile came too close to the aquatic passageways. They attacked with ferocity- one of them bit off Sauro-Hunter's hand. However, they were eventually beaten off or killed.
It is believed most of the race was killed during these battles, as when these passageways were used by the Trouble Sub to escape the Goo Caverns, they met little resistance. Shortly afterward, much of the Goo Caverns blew up. However, at least a few survived in the tunnels or escaped into the ocean, and they may remain a danger to Dino Attack Agents, Alpha Team Agents, or anyone who comes too close.
After rescuing Commander Frank Bowman from the wreckage of a shuttle, another former pirate Elizabeth Winsor encountered one of these surviving Octosaurs, although they were unaware of what it was. Due to her pirate background, Elizabeth actually believed it to be the Kraken. This Octosaur completely destroyed the Coast Guard patrol boat they were aboard.
An Octosaur, is technically speaking, a mutated Octopus. Due to the insertion of Mutant Dino DNA into their cells, Reptile nicknamed them Octosaurs. They are mutated creatures with immense strength, from even their youngest years. They are rarely found unless in extremely flooded areas, such as certain caves in the Goo Caverns. Octosaurs age quickly but also reproduce quickly, meaning that a handful of Octosaurs could replenish this deadly race.
The Octosaur young are capable of breathing on the surface and are amphibious. Such Octosaurs were the ones that attacked the Dino Attack Agents in the Goo Caverns, emerging from the water. As they age, they loose their amphibious capability and become incredibly massive beasts, capable of crushing even the largest ships and submarines easily.