[15.1] examine an opposum skull. 1. do you see evidence that the sense of smell is important to these animals? 2. note the way the triangular upper molars fit against the lower molars when the jaw is closed. this molar shape and occlusion is considered primitive because it resembles the arrangement in early fossil mammals. are the upper and lower tooth rows the same distance apart? is lateral (side-to-side) movement possible when chewing for opposums? 3. the primitive number of teeth in placental mammals is 44, but marsupials often have more teeth than this. is that the case with these specimens?