In the Beginning
It is the dawn of the Triassic Era. Among the reptilian survivors of the Permian catastrophe are the amphibious Crimson Croc and the nocturnal and intelligent Rabbit Croc. Mammals include the Two-Tusker, a grazing herbivore and the Dog-Face, a creature blessed with intelligence and swiftness. All are found in small but growing populations.

Triassic
The orders waste no time in evolving new forms. Incredibly, some Crimson Crocs manage to evolve into seed-eating winged doves while some Two-Tuskers rapidly develop speed to evolve into rabbits. The original forms quickly grow in size and number as they find that in many areas, size is the best way to survive. The Rabbit Crocs, finding themselves less and less able to exploit their limited ability to subsist on plants, switch to preying on the others. In similar straits, the Dog-Faces shrink and develop a high-stamina diaphragm which gives them the speed to hunt both the doves and the rabbits.

Diapsid reptiles invade from South America, displacing some Rabbit Crocs. In other regions, the Rabbit Crocs and Dog-Faces carefully control the populations of their prey. The world is split between the tiny and the enormous as the Crimson Crocs, Two-Tuskers and the Rabbit Crocs have reached a weight of 60 tonnes. This works in favor of the Dog-Faces, who, too small and too fast to be caught by any predators, begin to dominate many areas by converting to predation of the competition in some areas. The Two-Tuskers develop blubber.

There is a plankton upwelling in the Zechstein sea, replacing the land in the area. Meanwhile, the South American Diapsids go extinct when the Rabbit Crocs grow larger then they do. The first invaders from Asia, Brachiosaurs, establish themselves in Western Greenland.

The small, swift Dog Faces in their combined roles of herbivores and carnivores are the clearly dominant order at this stage.

Jurassic
The early stages of this period see geographical changes as continental drift causes mountains to push their way up in the Western Laramide while a marine environment dominated by ammonites appears in the eastern Epeiric and a mangrove environment in Panama.

But the orders are changing too. The Crimson Crocs develop an incredibly long swan neck and move into new areas where they feed off tall trees. The Dog Face continues to develop too, adding cheeks, palate and tongue in order to browse and graze better and then evolving into a second form: swine. Not to be left out, the Rabbit Crocs also evolve into a new form, that of very small ornithopods, which now take over from the Dog Faces the predation of the rabbits and doves, as well as preying on the Dog Faces themselves. No longer able to overrun other species, the Dog Faces start to die off.

Suddenly and without warning, there is worldwide Trypanomiasis Plague, which kills off the last remaining swine who had been peacefully grazing in the far north of Beringia. At this point, the remaining Dog Faces are limited to the mountains of the Laramide where their intelligence allows them to survive in this difficult environment.

Meanwhile the rabbits somehow develop wings and learn to fly, giving them clear dominance in the insectivorid environments while making them utterly uncatchable by any predator. The original Two Tusker is still developing also, adding a tripod stance, and now taking away the last home of the Dog Faces who go extinct.

The Jurassic closes with a bang as due to ocean absorption of carbon-dioxide, the earth enters a new Ice Age. Ice fills the Alberta Delta and the connection with South America is severed. There is widespread dislocation and loss of population. The Rabbit Crocs and their Ornithopods relations, predators all, are clear leaders at this stage with twice the population of any other single type. There is rough parity between the Crimson Croc and the Two Tusker families.

Early Cretaceous
In response to the catastrophe and the disappearance of many marine environments, the Crimson Croc shrinks to a size of one ton, simultaneously developing the ability to drink seawater. The Two Tusker also shrinks somewhat with its predator the Rabbit Croc following this trend.

The Crimson Croc also evolves into a turtle form, which preys on the existing Crimson Crocs. Herbivorous fabrosaurs try to enter from Asia, but lose out to the speedy flying rabbits. Other than this, the world is momentarily stable.

This is temporary as gymnosperms arise in the Western Epeiric, maple woodlands and oyster beds and clams in the Zechstein, west to east, and ray fin fish replace cycads in the Laurentian Shield.

The Rabbit Crocs evolve a marine form, the pliosaurs, which drive out the turtles and make them extinct. They also develop courtship behavior. The Dog Faces return as Plesiosaurs, dominating some deep water biomes.

The period ends with continued clear dominance of the Rabbit Croc family, then the Two-Tuskers, the lagging Crimson Crocs and then the Dog Faces, limited to only two marine areas.

Late Cretaceous
Prairies develop in the western Sierra Madre and Asian invaders in the form of herbivorous iguanadonts overtake Beringia, but the big event of this period is the trouble caused by Sunspots. The ice age worsens, ice overwhelms the desert sand dunes, but founders on the Palisades in the Laramide. Ice also overwhelms the Laurentian Shield. As a result the Dog Faces lose their marine homes and go extinct while the Crimson Crocs follow them into oblivion when marine placodont immigrants force them from their remaining habitats. They are preyed upon by the Plesiosaurs who also grow fatty humps during this period, while the Rabbit Crocs now sport a tail club.

The period ends with the continued dominance of the Rabbit Croc family, now predating every other life form apart from the winged rabbits and iguanadonts.

Tertiary
In this period, termite mounds appear in Panama, angiosperms in the eastern Laramide and rain forest develops in the eastern Gulf, but the real news is Cloudiness and changes to to the earth's albedo. The Hercynian mountains erode, ice appears in the Epeiric, but most significantly, the world is too frozen to sustain viable populations.

Fin
At it ends, the Rabbit Croc family of three predators has nearly one half the remaining population while the doves on the one hand and the winged rabbits and Two Tuskers on the other have equal-sized populations at just half the size.