During the scene with Amelia in the biology lab, Wei-Chen has an affinity to the teacher's lipstick-wearing monkey, who will not leave him alone. Wei-Chen can easily recognize that the monkey is actually a male, just as the monkey can actually recognize that Wei-Chen is a monkey himself.
Did the first vertebrates evolve during the mesozoic era? No. The 1st vertebrates appeared in the fossil record about 525 million years ago during the Cambrian Period.
So there we have it - the first animal on earth was a marine organism. It was not until 240 million years later that the first animal showed up on land. This was a four-legged amphibian called Ichthyostega, which is a Greek term meaning fish roof.