Crocodiles have a heart with four chambers (two connected to the lungs and two connected to the rest of the body) just like birds and mammals.
However crocodiles also have the ability to have their heart act as a three chambered heart to mix oxygenated and deoxygenated blood (through the foramen of Panizza) to slow down their metabolism.
The also have a further mechanism (a cog toothed valve) to completely block the flow of blood to the lungs when submerged.
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