One Of the avatar of Vishnu was Kurma – tortoise
He was part of Samudra manthan. When the deva and danava decided to churna the ocean of milk , they used Vasuki As the rope, mandara as the churn and they needed someone strong to support it.
So Vishnu appeared as the tortoise – upper half human and lower half tortoise and supported the churn
Of course the whole process is a description of how to reach samadhi. But that is a story for a different time
Why did I think of this ?
They just found remains of a tortoise that was the size of a car!
Bhavin