Written on September 5, 2005.
Turtles first appeared in our fossil record about two hundred million years ago, roughly that's when the mammals appeared. These reptiles are one of the great mysteries in evolution, because there is no record of the transitional species' that paved their way. Some believe that this is so because they evolved quite quickly.
Proganocheelyz, the oldest turtle fossil we have, was a three-foot long freshwater beast that rather resembled a modern snapping turtle.
Turtles made their way into our oceans almost immediately. Our fossil records suggest that various turtles evolved from marine reptiles to freshwater reptiles back and forth.
Several terrestrial species evolved into marine turtles. It happened, independently, thousands of times. The shell, originally designed as protection against stomping reptiles, and as a wintertime storehouse for minerals, became in the sea a catalyst of aerodynamics and an efficient anti-shark cage. Gigantism in sea turtles is considered an evolutionary reaction to the threat of both sharks, and the now extinct giant seafaring reptiles of the lost ages.
Today, of all these thousands of variations, only seven species survive. Six of these come from the same lineage, and thus all are somewhat similar in appearance. But the seventh - the leatherback - is a sole survivor of a lineage of massive and ancient mariners. In today's world of conservation imagery (Polar bears, Pandas, Siberian Tigers), it is extraordinary how little weight is given to this sea-flying vessel of the Triassic. The leatherback, about the size of a European car, has flippers like wings and can achieve enormous speeds - flying vertically 4,000 feet into the darkest depths, in search of its translucent lowlife lunches.
Its black body hosts a constellation of white stars, its leathery shell like an inverted hull. The leatherback is thought to be related to the most massive sea turtle to ever swim the seas. Archelon weighed 10,000 pounds. It rode the great sea that at one time composed the interior of North America.
Five of the other six turtles closely approximate our idea of the sea turtle. Like the leatherback, they lead a complicated life of vastly different stages.
The seventh turtle, the flatback, lives along the north and east coasts of Australia.