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.
Fossil evidence shows that the first placental mammals evolved during the early Paleogene Period (65.6 million to 23 million years ago), some 200,000 to 400,000 years after the extinction of the dinosaurs at the end of the Cretaceous Period (145.5 million to 65.5 million years ago).