Crocodiles and alligators.
They are rectangular.
Animal pupils come all different shapes and sizes. A cat has slit shaped pupils, and a chicken has round pupils. Some goats even have time glass shaped pupils. Many different shapes.
Hippopotamus
Goats have retagular shaped pupils.
cuttlefish
Sheep
The shape of an octopus' pupil is square-shaped.
It helps the pupil let in the right amount of light.
Goats. Also octopi. But octopi aren't mammals. Right?
Maltese painted frogs can have triangular shaped pupils. Please see the related link for more information...
No, it is not more likely that a non T-shaped belly button will eject a piercing when compared to a T-shaped navel.