En supposant l'absence du grand cataclysme qui a balayé de la surface de notre planète les grands dinosaures, Dixon propose une simple petite modification de notre préhistoire, qui lui permet de jeter les bases d'un nouveau déroulement de l'évolution des espèces.
De bout en bout, j'ai admiré l'audace de cette hypothèse. Et cette tentative est si enthousiasmante qu'elle mérite d'être baptisée d'un nom qui lui soit propre : La Zoologie Alternative.
Desmond Morris, préface (extrait.)
After some 50 million years of evolution these features have all developed again in one animal - the desert leaper, Aquator adepsicautus. The leaper is descended from the rodents, possibly one of the jerboas or sand rats, and has grown large - adult males may reach more than 3 metres from nose to tail. The tail is the most unusual feature of this animal; it is here that all its subcutaneous fat is stored. The fat is not a water store, but a store of food that enables the leaper to go for long periods without eating when food is unavailable. When the fat store is full the animal's body is well balanced and it can leap quickly along on its hind limbs. In this condition it can undertake journeys of 100 kilometres or more between waterholes and oases. It has broad, horny pads on the toes of its hind feet which prevent it from sinking into the sand and give it a good grip on naked rock
As the rats expanded to occupy the niches left by the dwindling carnivores their teeth evolved to fulfil their new role. The gnawing incisors developed long, stabbing points and were equipped with blades that could cut into and grip their prey. The gap between the incisors and the back teeth became smaller and the grinding molars became shearing teeth that worked with a scissor action. To make the dentition effective the jaw articulation changed from a rotary grinding motion into a more powerful up-and-down action. This dentition was crucial in the development of the predator rats and allowed them to radiate into the numerous forms and varieties seen throughout the world today.
The flooer, Florifacies mirabila, has remained an insect-eater, but is now largely sedentary. Its brightly coloured ears and nose flaps mimic a species of flower found on the islands. It sits among them with its face turned upwards, snapping at any insect that attempts to land.