Titanoboa
The largest known species of snake on the planet is the Mother Snake that's a tropical snake. It is a huge snake. There were many snakes that were as long as a school bus and as heavy as a car in the prehistoric days.
anaconda
the reticulated python is the largest snake
Basilosaurus
t.rex
Megaladon
The largest prehistoric animal ever was the Basilosaurus which was a 59 foot whale. The largest crocodilian was the 39 foot long Sarcosuchus Imperator.
The largest prehistoric mammal ever was the Indricotherium a prehistoric rhino like mammal the height of a modern giraffe and weighing 12 tons.
MegalodonOtodusPtychodusIsurus hastalisEdestus
sinead of course
The blue whale is the largest prehistoric animal, not including reptiles. Some prehistoric species of the blue whale were even larger than the current ones.
the would be the anaconda and the coral snake