IV
On the Cliffs of Time
Two hundred and twenty-five million years ago the earliest recognizable ancestors of the Tu-nel ruled the earth. They were the therapsids. Mammal-like reptiles.
There were also the dicynodonts, roaming in stupendous herds that stretched the horizon. The largest of these was the size of a rhinoceros.
But the Tu-nel originated with the cynodonts that preyed upon the herds. Their precursor was Cynognathus crateronotus, a carnivore with a dog-like visage and prominent fangs. Although only seven feet long, by working in packs they could bring down a large herbivore with relative ease.
On the early continents no other form of life challenged the mammal-like reptiles. Giant, primitive crocodiles patrolled the rivers. The long and slimy reptile Nothosaurus clambered over sun-baked rocks. But the broad vistas belonged to the creatures who were the forerunners of all mammals. For one hundred and thirty million years they unknowingly shaped the master plan of the planet. Someone from another world would have looked at their advanced metabolism, their enormous population, their variety and the sheer weight of invested evolution, and have little doubt that true mammals were on the verge of permanently conquering the land.
Then came the archosaurs.
The ensuing battle lasted thirty million years.
The defeat of the therapsids, the catastrophic faunal displacement, was final--almost. The various mammal-like reptiles either died out or slipped into the holes and crevices of history. For now, a mighty triumvirate of thecodontians ruled: the sluggish crocodilians, the flying pterosaurs... and the all-powerful dinosaurs. For one hundred and forty million years the mammal-like reptiles quailed in the shadows of cold-blooded reptiles and warm-blooded dinosaurs.
Not all of the defeated therapsids remained on land. A tiny handful took to the water. Among them were the proto-Tu-nel.
During the Jurassic and Cretaceous Periods a variety of elasmosaurs and pliosaurs swam the shallow seas in enormous reptilian schools. They now wrought havoc amongst the creatures that would one day resemble them so closely. The proto-Tu-nel were driven to the evolutionary wall. They were faced with four options: they could return to the rivers, retreat to the cold polar waters where reptiles could not follow, or fight back. They could also become extinct--extinction being an evolutionary choice.
Many millions of years later, in the Holocene Epoch, early cartographers would compile their meager information to create the first maps of the world. Those maps showed two huge (and for the most part mysterious) continents with a sea in the middle--the Mediterranean. It was as if they had seen the planet from space one hundred and forty million years earlier, for in the Late Jurassic, there were two huge (and for the most part mysterious) super-continents. To the north was Laurasia. To the south, Gondwanaland. The sea in the center was the Tethys Sea and it was there that one species of Tu-nel fought the plesiosaurs and ichthyosaurs for oceanic domination. This branch of the Tu-nel was wiped out in a brief but furious million years.
The polar Tu-nel never had much chance of success. Most of the primitive fish of the period remained in the tropics and sub-tropics. Whenever famine struck, the Tu-nel had to enter the warmer zones to find food. More often than not, they themselves became food as they entered the domain of the aquatic reptiles.
The riverine Tu-nel remained small, archaic--and alive. Like many of the therapsids before them, they had weaned themselves from the egg-laying habits of the amphibians and reptiles. They gave birth to live young. The newborns clung to their mothers' teats.
Once grown, quickness, intelligence and luck remained the keys to survival. The early Tu-nel could slip into the water when predators approached on land or race to the beach when a great croc angled towards them. They remained quadrupeds with webbed toes. Their powerful diamond-shaped flippers would come later.
Eventually, catastrophe overcame the dinosaurs. It began with a series of great ice ages. The oceans retreated from the fertile land. The food chain of the sea altered drastically. The reptilian serpents began to starve.
On land, hot-blooded dinosaurs had no problem with the lower temperatures. But when land bridges were exposed, herds that had been kept separate for geologic ages came into contact. The result was very much like that which would happen to the American Indians when the European explorers arrived. Sometimes entire herds were destroyed by disease. For three hundred thousand years the two dinosaur orders, Saurischia and Ornithischia, maintained a perilous hold. Many species were wiped out. But a few, such as the Stegosauria, clung tenaciously to their ancient foothold. For all their travails, it was beginning to seem dinosaurs would survive.
Then the asteroid hit.
The weakened structure that had supported the dinosaurs and marine reptiles collapsed.
The mammals emerged.
The Tu-nel emerged.
With the giant sea reptiles gone, the Tu-nel could once again venture into the wide ocean. There was competition, of course. Encounters with giant sharks rarely ended happily. But the attrition was never on the same scale as it had been during the Mesozoic. Over tens of millions of years, the Tu-nel became more streamlined, more pelagic. One breed, descended from the Tu-nel of Gondwanaland, sported necks that took up half their body length. What made them so imposing was their strength. Having descended from bull-necked cynodonts, their long necks were far sturdier than the sinuous extensions of the plesiosaurs, whose ancestors were slender-necked reptiles. This was to be a crucial feature in the next great challenge the Tu-nel faced.
The arrival of the first whales.