Which of the following is not related to studying the fossilized skeletons? 

"Carcasses" has nothing to do with the study of fossilized skeletons. 

The term "carcasses" refers to the dead body of an animal, usually one that was killed for food. In contrast, fossilized skeletons are the remains of ancient organisms that have been preserved in rocks over millions of years. 

The remaining three options – "Life span," "Medical pathologies," and "Growth patterns" – are all related to fossilized skeletons and can provide information about the biology and evolution of ancient organisms.