T h e E v o l u t i o n O f T u r t l e s

In the early Triassic, about 260 millions of years ago, appeared Captorhinus, a small reptile who

was the first reptile having a shell that covered his chest, organs, and also covered his ribs.

Fifty years later, in the upper Triassic appeared another group of reptiles similar of actual turtles, call Placodontos which now are extinct without evolutionary descent.

The firsts Testudines, from which actual turtles desced, appear about 200 millions of years ago, this animals had teeth in theirs mandible which

then envolved to a horny beak.

A good example of this primitive turtles is the gender Proganochelys who had a hard bony caparace similar of the actual turtles but it´s a

natomy shows that it is unlikely that he could hide his head, legs and tail in it´s caparace. They had a horny beak like actual turtles but also they had a few teeth. These teeth are an inheritance from their ancestors.

Marine turtles didn't appear until Jurassic (150 millions of years ago) although the heavy caparace was unfavorable to the marine conditions. Later, the turtles had not theeth and was able to hide they neck into the caparace and soon, turtles distinguished in two superfamilies: Criptódiros and Pleuródiros.

In the Cretaceus the caparace became light and the marine turtles were divide in four families only acuatics.

Aquatic and terrestrial turtles envolved along the time to

today, marine species changed little since their anatomy was very advanced but the terrestrial turtles was diversified into several lines that led to thousands of species.