The story goes that, in the 1930s, a Scottish naturalist named Hobard Quell went to South America and discovered a valley where dinosaurs had survived the extinction (all South American species, mind you).
After establishing it as a nature preserve and managing to acquire the valley, named Tierra Olvidada, under his ownership, via Quell Laboratories, he kept the place protected from poachers. Time passed and he was getting older, and in 1945, shortly before his death, he passed ownership to his son, Jonathan. Jonathan had no interest in the place, but instead was curious about a mysterious plant known as Amahirium, which was found only in the valley. He stripped the place to harvest this to make pharmaceutical drugs. Quell Laboratories used techniques they learned from the Amahirium Cartel to properly harvest and transplant the odd foliage to their uses, but this process caused any species to fall extinct once again.
When the public caught wind, conservation groups where formed, most notably the Paleo Patrol, an extremists dinosaur protection group, demanding for changes.
Time later, Jonathan died in an accident and his son, the infamous Samson Quell, takes over. Worst of all, he performs cruel experiments on the remaining dinosaurs and caused even more species to fall extinct. When the conservation groups, backed by the authorities, threatened to take the ownership away, Samson, in a desperate attempt, went to OnyxoCore, a genetics company that worked in tandem with Quell Laboratories back when Jonathan was in control.
OnyxoCore cloned brand new species to fill the gaps, including the Tyrannosaurus, the Dakotaraptor, and the Sinornithosaurus. Quell, however, secretly used these newly cloned species for his experiments. Dr. Jonah Onyx, founder of OnyxoCore, threat to expose Quell.
In order to prevent this, Quell contacted a disgruntled OnyxoCore employee, Dr. Dimitri Lambros, and the 2 conspired to.
murder Jonah; Quell so that he doesn't get exposed and Lambros so that he gains control of OnyxoCore. They poisoned Onyx, making everyone believe it was heart failure.
However, Miguel Onyx, Jonah's nephew, became head of OnyxoCore instead. Despite this, Quell promoted Lambros to be head scientist for Quell Laboratories, which made him defacto head of OnyxoCore (due to the partnership); he also gave him a private bungalow deep in the forest to perform his own sadistic experiments without interference from anybody.
However, there was a leak in the company, exposing Quell Laboratories. The Paleo Patrol demanded that a representative be onsight at all times, nominating Victor Martinez, the current vice president of Quell Laboratories; Victor is a compassionate man and was once a great lawyer, and he was chosen because of his empathy towards the Paleo Patrol and his high position.
Quell became even more desperate and demanded that OnyxoCore, against Miguel's wishes, design hybrid dinosaurs to experiment with. Quell's reasoning: "These hybrids technically don't exist, making them fully under our control. They have no rights."
It was shortly after this that the Quell Laboratories Incident (2001) occured...
And that's the build up

Yes, I have hybrids, but the story is not at all revolved around them; they only cause 1 "on-screen" death and nothing more. Most of the species I chose are gonna be scientifically accurate in design, with some theories thrown in on their behavior (and some of my own). For example, Sinornithosaurus (or Sinthies) are speculated to be venomous, so they will have venom in the book. Tropeognathus has a bonus club on its snout, so they will behave like flying battering rams...
SO far, I have 8/10 chapters done, and I just started chapter 9. When I'm done, I'm gonna post it on the Prehistoric Legacy fandom site (which is still in the works because there's only 3 of us working on it)