On the world Galapagon, the scientist Shh-Ell of an advanced race of turtles realised that their planet was doomed, and convinced the Science Council that they should build 1,000 spaceships to evacuate it. Slow by nature, the turtles only managed to build one spaceship, in which Shh-Ell's infant son, Tur-Tel was sent to Earth. Found by a kindly homespun farming couple, the turtle grew up and gained super-powers, becoming Super-Turtle, the Reptile of Steel.
[It is unclear on which pre-Crisis Earth, if any, the humorous adventures of Super-Turtle took place. There have been a couple of post-Crisis (non-canonical) appearances that fit in with the character's pre-Crisis history.]